ALBERT

Description: 〈p〉Publication date: Available online 8 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Jonas Henschel, Simon Wiemers-Meyer, Marcel Diehl, Constantin Lürenbaum, Wen Jiang, Martin Winter, Sascha Nowak〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The expansion of lithium ion battery (LIB) application is accompanied by the growth of battery pack sizes. This progression emphasizes the consideration of electrolyte safety as well as environmental aspects in case of abuse, accident, or recycling. Hexafluorophosphate is one of the most commonly used conducting salt anions in electrolytes. It has great potential to degrade to various acidic and non-acidic organo(fluoro)phosphates with presence of water and during battery cell operation. Consequently, toxicological investigation on these organo(fluoro)phosphates has emerged because they either have structural similarities as chemical warfare agents or play a widespread physiological role as phosphates in the human body. This circumstance underlines the need of isolated examination of these compounds for safety assessment. In this work, we used hydrophilic interaction liquid chromatography for the extraction of acidic organofluorophosphates from thermally aged LIB electrolytes. The developed two-step fractionation method provided high separation selectivity towards acidic head groups, which allowed the separation of undesired matrix and target compounds. These findings facilitate isolated toxicological investigations on organofluorophosphates that are beneficial for environmental and safety research, the battery cell industry, and human safety surveillance in regard to aged LIB electrolytes.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 3 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Fa Xu, Yun Huang, Shiyu Ding, Xu Cai, Chang Liu, Zhenni Ji, Jintian Tang, Yi Yang, Jing Tian〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉An efficient strategy for the selection of active components based on counter-current fractionation and bioassay-guided separation was established in the present work. 〈em〉Blaps rynchopetera〈/em〉 Fairmaire was an edible medicinal insect. Its extract showed the potential RAW264.7 macrophage cell inhibitory activity. After extraction with different solvents, the active components were enriched in ethyl acetate. In order to further track the active compounds, the ethyl acetate extraction was divided into 14 fractions by means of HSCCC. The results showed that the activities of F6 and F7 were significant higher than the others. Two compounds, hydroxytyrosol and 4-ethylbenzene-1,3-diol, were separated from the mixture of F6 and F7 by column chromatography and their chemical structures were confirmed by MS, 〈sup〉1〈/sup〉H NMR and 〈sup〉13〈/sup〉C NMR. The IC〈sub〉50〈/sub〉 of hydroxytyrosol and 4-ethylbenzene-1,3-diol against RAW264.7 macrophage cell were 38.24 ± 0.26 μg/mL and 103.26 ± 0.29 μg/mL, respectively, indicating that hydroxytyrosol was the major active ingredient responsible for the RAW264.7 inhibitory activity of 〈em〉Blaps rynchopetera〈/em〉 Fairmaire.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 2 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Crystal Sweeney, Yuri Park, Jong Sung Kim〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In the acidic environment of the stomach, nitrosatable pesticide residues may react with nitrite to form potentially carcinogenic pesticide-associated 〈em〉N〈/em〉-nitroso compounds (PANOCs). The objective of this study was to develop a method for the analysis of 10 nitrosatable pesticides and breakdown products in human serum and urine. Three sample preparation methods were evaluated for extraction of target analytes from the biomatrices. Deproteinization by methanol for 300-μL aliquots of serum with a final extract volume of 225 μL resulted in excessive ion enhancement of some analytes and suppression of others. Three types of solid-phase extraction cartridges were tested for optimal analyte retention from 200-μL aliquots of serum with a final extract volume of 400 μL; this approach resulted in significant analyte loss for some compounds. The Quick, Easy, Cheap, Effective, Rugged, and Safe approach resulted in a suitable method for extraction of the analytes from each biomatrix. Biofluid samples (500 μL) were spiked to 100 μg L〈sup〉−1〈/sup〉 with analytical standards and extracted using 500 μL of acetonitrile (ACN) with 4% acetic acid (AcOH) for serum and 0.1% AcOH in ACN for urine. For extraction, 200 mg magnesium sulfate (MgSO〈sub〉4〈/sub〉) and 50 mg sodium acetate were added for serum and 200 mg MgSO〈sub〉4〈/sub〉 and 50 mg sodium chloride were added for urine. Final extract volumes for both biomatrices using the QuEChERS method was 400 μL after dilution. Samples were analyzed via ultra-high pressure liquid chromatography/high-resolution accurate mass orbital ion trap mass spectrometry. Mean recoveries for target analytes in serum and urine ranged between 74 and 120% (%RSD 〈 12) and 96 to 116% (%RSD ≤ 10), respectively. These methods may be used in large-scale biomonitoring studies to analyze PANNs and their parent compounds in human serum and urine.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 2 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Jijie Kong, Fengxi Zhu, Wen Huang, Huan He, Jiapeng Hu, Cheng Sun, Qiming Xian, Shaogui Yang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, three kinds of Zeolite imidazolate framework-8 (ZIF-8), synthesized by solvothermal, stirring and ball-milling method, were fabricated on the stainless steel wire via sol-gel technique. These fibers were used as solid phase microextraction (SPME) coating materials and applied for analyzing 16 polycyclic aromatic hydrocarbons (PAHs) and 11 nitro polycyclic aromatic hydrocarbons (NPAHs) in environmental water samples by gas chromatography-tandem mass spectrometry (GC–MS). The optimal pH, ionic strength, extraction time, extraction temperature, desorption temperature and desorption time were 6.0, without salt addition, 45 min, 35 °C, 260 °C and 5 min, respectively. The extraction mechanism of the ZIF-8 fiber might be the hydrophobicity, molecular penetration and π-π stacking interactions. Under the optimized conditions, the as-proposed fiber provides a wide linearity range from 10 to 20,000 ng L〈sup〉−1〈/sup〉 and a low detection limit of 0.3–27.0 ng L〈sup〉−1〈/sup〉 for PAHs and NPAHs analysis. The single fiber and fiber to fiber relative standard deviations were observed in the range of 3.0%–13.9% and 3.5%–12.3%, respectively. The method shows great potential in environmental analysis field.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 2 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Natalja P. Nørskov, Søren Krogh Jensen, Martin Tang Sørensen〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Glyphosate is the most used herbicide in agriculture. To monitor glyphosate exposure, analytical methods have to fulfill requirements with regard to sensitivity, reproducibility, ease of handling/high-throughput and applicability to multiple biological matrices. Furthermore, the methods have to include the degradation product of glyphosate, aminomethylphosfonic acid (AMPA) and preferably metabolites of glyphosate and AMPA, 〈em〉N〈/em〉-acetyl AMPA and 〈em〉N〈/em〉-acetyl glyphosate. Majority of the published methods for glyphosate and AMPA require derivatization to be able to achieve high sensitivity. In this work, we present highly sensitive microLC–MS/MS method for simultaneous quantification of glyphosate, AMPA, 〈em〉N〈/em〉-acetyl AMPA and 〈em〉N〈/em〉-acetyl glyphosate in multiple biological matrices without derivatization. The combination of simple sample clean-up procedures for simultaneous handling of 96 sample and short chromatographic run of only 3.4 min, meets the requirements for high-throughput methods. Simple mobile phase of water containing formic and medronic acids and isocratic run provided robust chromatographic separation on hypercarb column. The use of micro-flow system decreased the background noise, increasing the sensitivity. Achieved Low Limits of Quantification (LOQs) for liquid samples (plasma/serum/urine) were 0.00005 mg L〈sup〉−1〈/sup〉 and 0.0001 mg kg〈sup〉−1〈/sup〉 for solid samples (grain and soybean based feed/stomach/gizzard/intestinal content), which is more than 100 time more sensitive compared to QuPPe-Method. The method was validated in representative matrices with minimum of five fortification levels, six measurements per spiked concentration and three batches. All the samples were spiked with corresponding internal standards for all four analytes before sample clean-up procedures, ensuring high accuracy and precision. Recoveries for plasma/serum ranged between 86–108%, urine 93–120%, feed 91–115% and stomach/gizzard/intestinal content 92–110% with precision below 20%. The method’s applicability was tested on 2000 samples measured during one year period.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 2 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): E. Peris-García, M.C. García-Alvarez-Coque, S. Carda-Broch, M.J. Ruiz-Angel〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In reversed-phase liquid chromatography, the performance for basic compounds is affected by the interaction of the protonated (cationic) species with the anionic free silanols on the alkyl-bonded stationary phases. Using aqueous-organic mobile phases in the absence of additives, the retention may be too high, and the peaks be broad and asymmetric. The performance is improved by addition to the mobile phase of ionic liquids, from which 1-hexyl-3-methylimidazolium chloride ([C〈sub〉6〈/sub〉MIm][Cl]) has especially good characteristics. A recent report has also revealed that the use of the phosphate system as buffer, at varying concentration and pH, may have a significant role in the chromatographic performance of basic compounds, with effects on both retention and peak shape. In this work, this study has been extended to other three buffer systems (acetate, citrate, and formate), at increasing concentrations and pH 3 and 7, in the presence and absence of [C〈sub〉6〈/sub〉MIm][Cl]. The results have been compared with those obtained with the phosphate system. The retention increases by addition of larger concentration of all buffers, in both absence and presence of [C〈sub〉6〈/sub〉MIm][Cl]. Without additive, peak performance is also enhanced significantly. This effect is minimal in the presence of [C〈sub〉6〈/sub〉MIm][Cl], which yields highly symmetrical peaks at all buffer concentrations, due to an effective blocking of the silanol activity.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 9 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Diana M. Cárdenas-Soracá, Felipe I. Tucca-Díaz, Claudia A. Mardones-Peña, Ricardo O. Barra-Ríos〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A novel strategy for the analysis of 20 organochlorine pesticides (OCPs) monitoring in marine surface waters through ethylenevinyl acetate (EVA) passive samplers was developed and validated. The approach is based on the coupled of ultrasound-assisted solvent extraction (UASE) and headspace solid-phase microextraction (HS-SPME) as extraction method for OCPs from EVA samplers. The UASE-HS-SPME method was optimized with a 27-4 Plackett-Burman design, while the significant factors (salting out, temperature and extraction time) were optimized using a central composite design (CCD) combined with desirability function (DF). The OCPs detection was performed using multiple reaction monitoring (MRM) by gas chromatography-tandem mass spectrometry (GCMS/MS). The optimum experimental conditions comprised: salting out: 23% wv-1 NaCl, temperature: 75°C and extraction time: 55 min. The optimized method was validated in terms of linearity (R2〉0.9946), recovery (〉61%) and inter-day and intra-day reproducibility (〈19%) for 20 OCPs studied. The limits of detection (LODs) were ranging from 0.01 ng for α-hexachlorocyclohexane and 0.27 ng for endrin aldehyde. Finally, the methodology was tested in marine surface seawater of Southern Chile using EVA samplers, where twelve OCPs were detected at ultra-trace levels (ngL-1).〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 3 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Maria Marioli, Ü. Bade Kavurt, Dimitrios Stamatialis, Wim Th. Kok〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In the present proof-of-concept study, we demonstrate that retention time, selectivity and resolution can be increased in asymmetrical flow field-flow fractionation (AF4) by introducing microstructured ultrafiltration membranes. Evenly spaced micron-sized grooves, that are placed perpendicular to the channel flow on the accumulation wall of a field-flow fractionation system, cause a decrease in the zone velocity which is stronger for larger solutes. This has been demonstrated in thermal field-flow fractionation, and we prove that this is also the case in AF4. We examine the hypothesis theoretically and experimentally, by both computational and physical experiments. By means of moment analysis, we derive theoretically a set of equations which, under certain conditions, describe the mass transport and relate retention time, selectivity and plate height to the dimensions of the grooves. Physical experiments are carried out using microstructured polyethersulfone membranes fabricated by hot embossing, and the experimental results are compared with computational fluid dynamics experiments.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 9 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Yu-jia Zhang, Yuan Zhang, Yu Zhou, Guo-hui Li, Wen-zhen Yang, Xue-song Feng〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Biogenic amines (BAs), mainly produced by amino acid decarboxylation, are widespread in foods and human organisms. Appropriate intake of BAs is beneficial to the human body, while excessive consumption may cause discomfort. Meanwhile, BAs are a kind of chemical marker for evaluating meat freshness. For these reasons, simple, rapid and efficient methods have been developed for the determination of BAs in food and biological products. This review introduces the provenance, classification and physiological activity of eight essential BAs and summarizes the dominant pretreatment and analysis methods since 2010. Pretreatment technologies mainly include the “dilute and shoot” method, ultrasonic assisted extraction, solid-phase extraction, matrix solid-phase dispersion, dispersive liquid-liquid microextraction, etc. Determination methods include liquid chromatography coupled to ultraviolet or fluorescence detectors, liquid chromatography tandem mass spectrometry, capillary electrophoresis, biosensors and so on.〈/p〉〈/div〉

Description: 〈p〉Publication date: 11 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1603〈/p〉 〈p〉Author(s): 〈/p〉

Description: 〈p〉Publication date: Available online 17 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): J.F. Ayala-Cabrera, E. Moyano, F.J. Santos〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this work, the suitability of gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the multi-class determination of different families of neutral per- and polyfluoroalkyl substances (PFASs), such as fluorotelomer olefins (FTOs), alcohols (FTOHs) and fluorooctanesulfonamides (FOSAs) and sulfonamido-ethanols (FOSEs), was investigated and compared. Regarding GC-MS, the use of a semi-polar GC column (DB-624, 6%-cyanopropilphenyl 94%-dimethyl polysiloxane) allowed the adequate separation of all the compounds while chemical ionisation (CI) of positive ions as ionisation technique provided the best responses. Concerning UHPLC-MS/MS, atmospheric pressure chemical ionisation (APCI) and photoionisation (APPI) sources allowed the ionisation of all studied neutral PFASs, including FTOs for the first time. High vaporizer temperatures (450 °C) and acetonitrile/water mobile phase mixtures were required to favour the ionisation of FTOs, with adequate ionisation for FTOHs, FOSAs and FOSEs. The chromatographic separation, performed on a totally porous column (Luna C18), allowed the successful separation of the four families of neutral PFASs. After comparing the performance of the studied methods, the highest detectability was achieved using UHPLC-APCI-MS/MS and it was chosen in combination with a solid-phase extraction (SPE) procedure for the analysis of neutral PFASs in water samples. The whole method provided low limits of detection (0.003 to 6 µg L〈sup〉–1〈/sup〉), good precision (RSD 〈 9%) and trueness (relative error 〈 10%). The methodology was applied to the analysis of river water samples and the presence of some neutral PFASs were detected (8:2 FTO) and quantified (4:2 FTOH and 〈em〉N〈/em〉-EtFOSA) at low concentration levels (ng L〈sup〉–1〈/sup〉).〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 14 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Mengjie Qie, Yan Zhao, Shuming Yang, Wei Wang, Zhenzhen Xu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In order to address the specific question of food safety in livestock and poultry, it is imperative to monitor veterinary drugs at every moment in the process of livestock and poultry breeding. Thus, multi-residue analysis of a wide variety of drugs using ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) has become a tool of critical significance, especially for veterinary drug monitoring programs. A total of 160 compounds, belonging to 17 different families of veterinary drugs, were investigated in the urine and blood of livestock and poultry. Drug samples were extracted using a slightly acidic acetonitrile solution. The QuEChERS (quick, easy, cheap, effective, rugged, and safe) preparation method, combined with dispersive solid phase extraction (d-SPE) was compared with the approach of solid phase extraction (SPE). In the end, the QuEChERS extraction procedure was selected to reduce matrix effects and efficiently extract target veterinary drugs, and d-SPE was applied as a cleanup step. Electrospray ionization coupled with positive dynamic multiple reaction monitoring (dMRM) was utilized for the analysis of 160 different drugs in a single chromatographic run of 24 min. The efficiency of this method was evaluated using 7 matrices (pig blood, cattle blood, sheep blood, chicken blood, pig urine, cattle urine, and sheep urine). Good linearity was obtained for the analytes in a concentration range of 1–100 ng/mL, with correlation coefficients higher than 0.990. Most of the 160 drugs studied gave estimated limits of detection (LOQs) of 1 ng/mL, with some LOQs reaching as much as 5 ng/mL. The mean recoveries at four spike-in levels of 1, 5, 10, and 50 ng/mL, ranged from 60% to 120%. The intra-day precision measurements had coefficients of variation (n = 6) 〈 15%, and the inter-day precision measurements were below 25%. Our method was applied in real samples and proved to be adequate for routine analysis. The proposed method proved to be simple, rapid and reliable for monitoring 160 drugs in the urine and blood of livestock and poultry, and can also be used for food safety monitoring.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 12 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Laura Akbal, Gérard Hopfgartner〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The application of supercritical fluid chromatograph with mass spectrometric (MS) detection (SFC-MS) was compared towards generic reversed phase liquid chromatography (RPLC) and hydrophilic interaction liquid chromatography (HILIC) for the analysis of urine with regards of ionization performance and analyte identification. The different chromatographic conditions were characterized with a selected set of 51 metabolites from different classes reported in the Human Metabolome DataBase (HMDB) and previously detected in human urine and/or plasma. SFC using a diol column with a gradient of carbon dioxide (CO〈sub〉2〈/sub〉) and methanol with 10 mM ammonium hydroxide as modifier was able to retain and separate twenty polar analytes co-eluting in the RPLC eluent front. In the conditions investigated and compared to HILIC where many metabolites were also co-eluting, SFC showed a different ratio between elution domain and analysis time. Similar peak width and symmetry were observed, while retention time variability was slightly lower compared to that of HILIC (0.15% versus 0.24% and 1.26% for RPLC and HILIC, respectively). In SFC-MS, a significant signal enhancement (2-150 times, average of about 10 times) was measured after post-column make-up addition (MeOH/H〈sub〉2〈/sub〉O, 95/5, v/v + 25 mM ammonium acetate) for twenty-eight analytes. Nine analytes measured by LC-MS could not be detected in SFC-MS. Applicability of SFC-MS for metabolomics was investigated with the analysis of urine samples using data independent acquisition (DIA) and more specifically Sequential Window Acquisition of all Theoretical Mass Spectra (SWATH/MS). Using a metabolomics library, 74 metabolites from human urine could be identified in positive mode in a single SFC-MS analysis of 15 minutes.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 11 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Mattias Sörengård, Vera Franke, Rikard Tröger, Lutz Ahrens〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Syringe filters are used to separate solids from liquids prior to analysis of poly- and perfluoroalkyl substances (PFASs). This is a critical step in sample preparation, as losses of PFASs to the filter material can be significant and lead to underestimation. This study evaluated losses of 21 PFASs in three different matrices (methanol, MilliQ water, and water containing 10 mg L〈sup〉-1〈/sup〉 dissolved organic carbon (DOC)) to six different types of syringe filter (0.45 and 0.22 〈em〉µ〈/em〉m). Regarding sample matrix, the lowest average ∑〈sub〉21〈/sub〉PFAS losses were observed in methanol (13%), followed by DOC water (19%) and MilliQ water (26%). Regarding syringe filter material, the lowest average losses of ∑〈sub〉21〈/sub〉PFAS in DOC water and MilliQ water were observed for a recycled cellulose filter (average losses 16% and 21%, respectively), while a polypropylene filter had the lowest ∑〈sub〉21〈/sub〉PFAS losses in methanol (9%). A smaller polyethersulfone (PES) filter (0.22 〈em〉µ〈/em〉m, 17 mm Ø) showed significantly (〈em〉p〈/em〉 〈 0.05) lower ∑〈sub〉21〈/sub〉PFAS losses in DOC water (on average 7.3%) than a larger PES filter (0.45 〈em〉µ〈/em〉m, 37 mm Ø) (23%). In DOC water, losses to the filter increased by 3.8%, 5.1%, and 8.4% per CF〈sub〉2〈/sub〉-moiety for C〈sub〉3〈/sub〉-C〈sub〉11〈/sub〉 perfluoroalkyl carboxylates (PFCAs), perfluoroalkyl sulfonates (PFSAs), and fluorotelomer sulfonic acids (FTSAs), respectively. Comparing different functional groups of PFASs, losses increased as follows: PFCAs 〈 PFSAs 〈 FTSAs 〈 perfluorooctanesulfonamides (FOSAs). Thus, care is needed when including filtration in PFAS analysis, since losses can be significant (up to 100%) depending on the type of syringe filter, target PFAS, and matrix.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 10 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): T. Alvarez-Segura, S. López-Ureña, J.R. Torres-Lapasió, M.C. García-Alvarez-Coque〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Multi-linear gradients are a convenient solution to get separation of complex samples by modulating carefully the gradient slope, in order to accomplish the local selectivity needs for each particular solute cluster. These gradients can be designed by trial-and-error according to the chromatographer experience, but this strategy becomes quickly inappropriate for complex separations. More evolved solutions imply the sequential construction of multi-segmented gradients. However, this strategy discards part of the search space in each step of the construction and, again, cannot deal properly with very complex samples. When the complexity is too large, the only valid alternative for finding the best gradient is the use of global search methods, such as Genetic Algorithms (GAs). Recently, a new global approach where the level of detail is increased along the search has been proposed, namely Multi-Scale Optimisation (MSO). In this strategy, cubic splines are applied to build intermediate curves to define any arbitrary solvent variation function. Subdivision schemes are used to generate the cubic splines and control their level of detail. The search was subjected to a number of restrictions, such as avoiding long elution and favouring a balanced peak distribution. The aim of this work is evaluating and comparing the results of GAs and MSO. Both approaches were tested with a set of 14 diuretics and probenecid, eluted with acetonitrile-water mixtures using a C18 column. Satisfactory baseline resolution was obtained with an analysis time of 15‒16 min. We found that GAs optimisation offered results equivalent to those provided by MSO, when the penalisation parameters were included in the cost function.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 6 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Adrian Sanden, Susanna Suhm, Matthias Rüdt, Jürgen Hubbuch〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉PEGylation of biological macromolecules is a well-established strategy to increase circulation half-life, decrease renal clearance and improve biocompatibility. PEGylation is a process in which polyethylene glycol (PEG) is covalently attached to a target molecule. The production of PEGylated biopharmaceuticals is usually executed by first producing and purifying the base molecule followed by the PEGylation reaction and purification of the modified molecule. Most PEGylated pharmaceuticals are produced by random PEGylation in batch mode and need to be purified as mainly the mono-PEGylated form is the desired drug product. In this work we propose a method to estimate the degree of PEGylation (DOP) of modified protein eluting from a chromatography column in near real-time. extended multiplicative signal correction (EMSC) is used in conjunction with asymmetric least squares (aaLS) to alleviate the influence of a salt gradient during ion exchange chromatography (IEX) on the spectral data. To convert the raw data obtained from spectral data to the actual DOP additional information obtained from off-line measurements is utilized. Once the signal correction is applied to in-line spectral data the DOP can be estimated without further use of off-line analytics. As the prerequisites for the application of this method are relatively easy to obtain it may also find use to speed up process development.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 5 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Niloofar Jalilian, Homeira Ebrahimzadeh, Ali Akbar Asgharinezhad〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In the current study, MMWCNTs@MIL-101(Cr) (Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉/multiwalled carbon nanotubes/MIL-101(Cr)) was synthesized and utilized as a new sorbent for the first time. It was employed successfully for the extraction of parabens and phthalate esters (PEs) from water and cream samples prior to their quantification with HPLC-DAD. The prepared metal-organic-framework (MOF) was characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), energy-dispersive X-ray spectroscopy (EDX), EDX mapping, thermogravimetric analysis (TGA), vibrating-sample magnetometer (VSM) and X-ray powder diffraction (XRD). Three phthalate esters (dimethyl phthalate (DMP), diethyl phthalate (DEP), diallyl phthalate (DAP)) and two parabens (methylparaben (MP) and butylparaben (BP)) were chosen as model analytes. Several experimental factors affecting the extraction efficiency, including pH value, nanosorbent amount, sorption time, salt concentration, sample volume, type and volume of the eluent, and elution time were investigated. The optimization of the extraction method was carried out by response surface methodology (RSM) and desirability function (DF) approach. Under the opted conditions, the method was linear in the range of 0.1-1500 μg L〈sup〉-1〈/sup〉 with coefficients of determination 〉 0.9991. The limits of detection of PEs and parabens were found in the range of 0.03-0.15 μg L〈sup〉-1〈/sup〉 (S/N = 3). The relative standard deviations were less than 7.5% and the extraction recoveries ranged from 38.04 to 70.62%. The present method was simple, rapid, inexpensive and environmentally friendly and was successfully utilized for the determination of PEs and parabens in water samples and various types of cream samples with satisfactory results.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 1 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Carlos Ramos-Contreras, Estefanía Concha-Graña, Purificación López-Mahía, Francisco Molina-Pérez, Soledad Muniategui-Lorenzo〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A green analytical methodology for the determination of 16 priority polycyclic aromatic hydrocarbons (PAHs) and 8 related compounds in air particulate matter was developed and validated. The method was based on pressurized hot water extraction (PHWE) followed by miniaturized membrane-assisted solvent extraction (MASE) and programmed temperature vaporization-gas chromatography-ion trap tandem mass spectrometry detection (PTV-GC-MS/MS). The parameters studied for PHWE were percentage of organic modifier (25 % MeOH), temperature (200 °C) and static extraction time (5 min). For MASE, extraction temperature (30 °C), time (90 min) and effect of an organic modifier were also optimized. The matrix effect was evaluated and compensated using deuterated labelled standards as surrogates for the quantitation of the target compounds. The analytical performance of the method was satisfactory: relative recoveries varied between 78 and 118% and repeatability and intermediate precision were 〈22% for all compounds. The Method Quantitation Limits (MQL) ranged from 0.9 (TPY) to 75.6 pg m〈sup〉−3〈/sup〉 (NAP). Satisfactory results for accuracy and traceability were evidenced by the analysis of a reference material (SRM 1649b) and comparison with previously published methods. The greenness score was estimated and compared with other techniques widely used for the analysis of PAHs in particulate matter, having a lower relative environmental impact.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 31 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Cornelius C.W. Willacey, Martijn Naaktgeboren, Edinson Lucumi Moreno, Agnieszka B. Wegrzyn, Daan Van der Es, Naama Karu, Ronan M.T. Fleming, Amy C. Harms, Thomas Hankemeier〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Recent advances in metabolomics have enabled larger proportions of the human metabolome to be analyzed quantitatively. However, this usually requires the use of several chromatographic methods coupled to mass spectrometry to cover the wide range of polarity, acidity/basicity and concentration of metabolites. Chemical derivatization allows in principle a wide coverage in a single method, as it affects both the separation and the detection of metabolites: it increases retention, stabilizes the analytes and improves the sensitivity of the analytes. The majority of quantitative derivatization techniques for LC-MS in metabolomics react with amines, phenols and thiols; however, there are unfortunately very few methods that can target carboxylic acids at the same time, which contribute to a large proportion of the human metabolome. Here, we describe a derivatization technique which simultaneously labels carboxylic acids, thiols and amines using the reagent dimethylaminophenacyl bromide (DmPABr). We further improve the quantitation by employing isotope-coded derivatization (ICD), which uses internal standards derivatized with an isotopically-labelled reagent (DmPABr-D〈sub〉6〈/sub〉). We demonstrate the ability to measure and quantify 64 central carbon and energy-related metabolites including amino acids, N-acetylated amino acids, metabolites from the TCA cycle and pyruvate metabolism, acylcarnitines and medium-/long-chain fatty acids. To demonstrate the applicability of the analytical approach, we analyzed urine and SUIT-2 cells utilizing a 15-minute single UPLC-MS/MS method in positive ionization mode. SUIT-2 cells exposed to rotenone showed definitive changes in 28 out of the 64 metabolites, including metabolites from all 7 classes mentioned. By realizing the full potential of DmPABr to derivatize and quantify amines and thiols in addition to carboxylic acids, we extended the coverage of the metabolome, producing a strong platform that can be further applied to a variety of biological studies.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 17 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Alejandro Fernández-Pumarega, José Luís Dores-Sousa, Sebastiaan Eeltink〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The present study reports on the analysis of different factors affecting the magnitude of the peak capacity for intact protein separations conducted in gradient reversed-phase liquid chromatography. Experiments were conducted using a 200 µm i.d. capillary styrene-〈em〉co〈/em〉-divinylbenzene monolithic column that was developed in-house and was characterized by a mode globule cluster size of 1.2 µm and a mode macropore size of 1.0 µm (based on scanning electron microscopy). The monolith yielded a minimum plate-height value of 13.3 µm for uracil. The use of trifluoroacetic acid instead of formic acid as ion-pairing agent generally led to better peak symmetry, narrower peak widths which effect is protein-dependent, and improved loadability characteristics. The peak capacity has been systematically assessed at different flow rates and gradient duration. The highest peak capacity of 247 was obtained at a flow rate of 1 µL•min〈sup〉−1〈/sup〉 and a gradient time of 120 min, which corresponds to an optimal 〈em〉t〈sub〉G〈/sub〉〈/em〉/〈em〉t〈sub〉0〈/sub〉〈/em〉 ratio of ∼60. While the optimum van Deemter velocity for intact proteins was approximated to be 0.065 µL•min〈sup〉−1〈/sup〉, the highest peak capacity was achieved at approximately 20-fold higher flow rate, depending on the gradient duration applied and the molecular weight of the proteins. The optimum velocity increased with decreasing gradient time and is a compromise between the magnitude of the mass-transfer contribution (decreasing the peak capacity with velocity) affect by molecular diffusion, and the increase in peak capacity induced by the more favorable gradient-volume ratio.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 15 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Nan Li, Jing Qiu, Huiying Liu, Zhijun Chen, Yongzhong Qian〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Oligo(ethylene glycol)-based thermoresponsive polymers with Wulff-type boronate affinity were anchored on magnetic nanoparticles. The resultant magnetic nanoparticles were used as sorbents for extracting luteolin, a 〈em〉cis〈/em〉-diol-containing model analyte. By exploiting the thermoresponsive properties and Wulff-type boronate affinity of the sorbents, target adsorption at room temperature (25 °C) and target release at high temperature (40 °C) were achieved under neutral conditions without pH alteration. The proposed thermoregulated extraction method was favorable for automated boronate affinity extraction, preventing degradation of the target and avoiding acidic elution for breaking Wulff-type boronate sites. Compared to reported sorbents for extracting luteolin, the sorbents possessed higher maximum adsorption capacity (98.7 mg g〈sup〉-1〈/sup〉) with acceptable sensitivity, simplified operation procedure, and mild extraction condition. Furthermore, the sorbents were applied in thermoregulated extraction of luteolin from honey samples. Satisfactory recoveries in the range of 83.2% ˗ 89.1% with RSD ranging from 2.2% to 4.6% were achieved. The results demonstrated that this work provided a new research direction to design and synthesize efficient thermoresponsive materials for recognition and release of 〈em〉cis〈/em〉-diol compounds under neutral conditions.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 9 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Joaquin Hernández-Fernandez, Erika Rodríguez〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper describes a new method for the effective extraction of the residues of five synthetic phenolic antioxidants (AOs): Ditertbutylphenol (DTF), Irganox 1010, Irganox 1076, Ethanox 330 and Cyanox 1790, from industrial water produced during the polypropylene (PP) deodorization process. In the deordorization process, PP is stored in a column for an average time of four hours and exposed to nitrogen and water vapor to remove inflammable compounds which may generate atypical odors in the PP. The samples of interest were taken in the desorber, followed by cleansing and pre-concentration using modified styrene divinylbenzene polymer cartridges. Liquid chromatography was performed with a reversed phase column and diode array. The method was validated for linearity, recovery, precision, specificity, limits of detection (LOD) and limits of quantification (LOQ). The chromatographic method showed LOQ from 5.4 to 16 mg L〈sup〉-1〈/sup〉 and LOD between 1.6 and 4.8 mg L〈sup〉-1〈/sup〉. The worldwide challenge to develop an analytical methodology which incorporates SPE with HPLC to identify and quantify AOs in industrial wastewater is addressed in this study. The recovery percentages were above 90% for most AOs, except for Irganox 1076 which showed a value of 83.2%. The ability to separate these five AOs of most frequent use worldwide, permits precision of measurement of the degree of contamination, making it useful for environmental regulation and the protection of public health.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 7 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Martin Eckardt, Marie Kubicova, Duyen Tong, Thomas J. Simat〈/p〉

Description: 〈p〉Publication date: Available online 8 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Muhammad Imran Malik〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉At the borderline between size exclusion chromatography (SEC) and interaction chromatography (IC) there is a special mobile phase composition and temperature at which polymer chains become “chromatographically invisible”. This point is termed as “chromatographic critical point” and chromatographic separations performed using these conditions are called “liquid chromatography at critical conditions” (LCCC). LCCC is a powerful technique in the analysis of functional polymers and block copolymers. At these so-called critical conditions molar mass discrimination of any specific homopolymer is suppressed rendering elution of whole range of molar mass at same elution volume. These conditions allow enhanced separation with regard to non-critical segment either in exclusion or interaction regime of the polymer chromatography. This article is intended to critically discuss different parameters that can be maneuvered to improve separation and in turn characterization of non-critical segment of block copolymers at LCCC. Different experimental parameters evaluated in this study include pore size of the column, mobile phase composition, temperature and gradients. These parameters can be adeptly adjusted to improve separation of non-critical segment while keeping the other segment close to critical conditions. Current study demonstrates that pore diameter and mobile phase are the only practical variable that can be used for improvement of characterization of non-critical block in the block copolymer while non-critical block is in exclusion regime. On the other hand, pore diameter of the column, temperature, solvent composition and gradients are important parameters that can be skillfully tuned for improvement of separation of non-critical block while non-critical block elutes in interaction regime. The above-mentioned variations are evaluated for di-block as well as tri-block copolymers of A-B-A and B-A-B type. Moreover, LCCC-IC is especially important for analysis of poloxamers.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 5 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Guoxiu Cao, Nian Wang, Dandan He, Xinmiao Wang, Yang Tian, Ning Wan, Wenchao Yan, Hui Ye, Haiping Hao〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The characterization of metabolome for poorly absorptive natural medicines is challenging. Previous identification strategy often relies on nontargeted scanning biological samples from animals administered with natural medicines in a data-dependent acquisition (DDA) mode by LC-MS/MS. Substances that displayed significant increases following drug administration are thus assigned as potential metabolites. The accurate 〈em〉m/z〈/em〉 of precursors and the corresponding MS/MS fragment ions are used to match with herbal ingredients and to infer possible metabolic reactions. Nevertheless, the low concentration of these metabolites within complex biological matrices has often hampered the detection. Herein we developed a strategy termed intestinal mucosal metabolome-guided detection (IMMD) to tackle this challenge using ginkgo biloba (GBE) as an example. The rationale is that poorly absorptive natural products are usually concentrated and extensively metabolized by enterocytes before they enter the blood stream and distribute to other organs. Therefore, we firstly identified the metabolites from intestinal mucosa of GBE-treated rats, and then used the identified intestinal mucosal GBE metabolome as targeted repository for MRM analysis. The presences of these metabolites were subsequently examined in rat plasma, liver and brain. The resultant GBE metabolome showed significantly improved coverage with 39, 45 and 6 metabolites identified in plasma, liver and brain compared to 22, 16 and 0 metabolites from the corresponding regions via the DDA-based strategy. In addition, we integrated the previously reported nontargeted diagnostic ion network analysis to facilitate the characterization of GBE components, and a chemicalome-metabolome matching approach (CMMA) to assist the identity assignment of GBE metabolome with IMMD. Combinatorially, we establish a multi-faceted platform to streamline the workflow of metabolome characterization for herbal medicines of low bioavailability. The metabolome information is expected to shed light on the elucidation of metabolic pathways for natural products, and the underlying mechanisms of their biological efficacies.〈/p〉〈/div〉

Description: 〈p〉Publication date: 27 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1602〈/p〉 〈p〉Author(s): 〈/p〉

Description: 〈p〉Publication date: Available online 15 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Federica Ianni, Francesca Blasi, Danilo Giusepponi, Alice Coletti, Francesco Galli, Bezhan Chankvetadze, Roberta Galarini, Roccaldo Sardella〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉α-linolenic acid (ALA) and its most important positional isomer γ-linolenic acid (GLA), are essential fatty acids (vitamin F). Therefore, ALA- and GLA-rich edible oils hold great potential in human and animal nutrition, as well as in nutraceutics and cosmetics. Quality control and nutritional validation of oil products is thus of increasing importance. In the present study, the cellulose tris(3,5-dichlorophenylcarbamate)-based chiral stationary phase was successfully used for separation of ALA and GLA, a major challenge in the liquid chromatography of these isomers. The chromatographic conditions were firstly optimized on a HPLC system with UV detection, and the use of a reversed-phase eluent system made up of aqueous 10 mM ammonium acetate/acetonitrile (40/60, v/v; 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈msubsup〉〈mrow〉〈/mrow〉〈mi〉w〈/mi〉〈mi〉s〈/mi〉〈/msubsup〉〈mi〉p〈/mi〉〈mi〉H〈/mi〉〈mspace width="0.33em"〉〈/mspace〉〈/mrow〉〈/math〉6.0) with a 25°C column temperature resulted optimal for the simultaneous discrimination of the two isomers at a 0.5 mL/min flow rate (α=1.10; R〈sub〉S〈/sub〉=1.21). The method was then optimized for LC-MS/MS implementation.〈/p〉 〈p〉The proposed innovative separation method holds a great potential for the quantification of ALA and GLA in food and biological matrices, thus opening the way to further investigations involving the two positional isomers.〈/p〉 〈/div〉

Description: 〈p〉Publication date: Available online 13 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Kanji Miyabe〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A moment analysis method is effective for the kinetic study of intermolecular interaction and solute permeation at the interface of spherical molecular aggregates. Association and dissociation rate constants of intermolecular interactions or the rate constants of interfacial solute permeation can be determined on the basis of the moment theory from the first absolute and second central moments of elution peaks measured by affinity capillary electrophoresis (ACE) or electrokinetic chromatography (EKC). In this study, it was discussed how the experimental conditions concerning the concentration of ligand molecule or molecular aggregate should be optimized in ACE or EKC experiments in order to determine the rate constants as accurately as possible. At first, peak broadening due to axial diffusion, reaction kinetics of intermolecular interaction, and mass transfer kinetics of interfacial solute permeation was quantitatively evaluated under hypothetical ACE or EKC conditions, which were chosen on the basis of our previous studies. Second, it was confirmed that some rate constants were determined in the previous studies from ACE and EKC data measured under appropriate experimental conditions. Then, a procedure was considered for determining more accurate analytical results of the objective rate constants from ACE or EKC peaks experimentally measured.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 12 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Giovanni D’Orazio, Chiara Fanali, Salvatore Fanali, Alessandra Gentili, Bezhan Chankvetadze〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In the present study separation of enantiomers of some chiral neutral and weakly acidic analytes was investigated on the chiral stationary phase (CSP) made by covalent immobilization of amylose tris(3-chloro-5-methylphenylcarbamate) onto silica in nano-liquid chromatography (nano-LC) and capillary electrochromatography (CEC) in acetonitrile and aqueous acetonitrile. Few comparisons were made also between the enantioseparations in nano-LC and high-performance liquid chromatography (HPLC) with the chiral column of 4.6 × 250 mm dimension. Slightly better separation of enantiomers was observed in HPLC mode compared to nano-LC mode. It was shown that in the capillary columns packed with the CSP containing about 20% (w/w) of a covalently immobilized neutral chiral selector, amylose tris(3-chloro-5-methylphenylcarbamate), sufficient electroosmotic flow has been generated and enantioseparations with reasonable analysis time were performed also in CEC mode. It was shown once again that CEC offers a clear advantage over nano-LC from the viewpoint of plate numbers and peak resolution.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 28 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Päivi Pöhö, Karen Scholz, Niina Kärkkäinen, Markus Haapala, Heikki Räikkönen, Risto Kostiainen, Anu Vaikkinen〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A new heated capillary photoionization (CPI) ion source design was developed to photoionize analytes inside a transfer capillary between a gas chromatograph (GC) and a mass spectrometer (MS). The CPI setup included a wide, oval-shaped vacuum-ultraviolet (VUV) transparent magnesium fluoride (MgF〈sub〉2〈/sub〉) window to maximize photoionization efficiency and thus sensitivity. The source contained a nitrogen housing around the ionization chamber inlet to avoid undesirable hydrolysis and oxidation reactions with ambient air and to maximize the proportion of formed molecular radical cations of analytes. The feasibility of the ion source was studied by analyzing 18 endogenous steroids in urine as their trimethylsilyl (TMS) derivatives with gas chromatography-tandem mass spectrometry (GC-MS/MS). The method was validated and applied to human urine samples. To our best knowledge, this is the first time that a capillary photoionization ion source has been applied for quantitative analysis of biological samples. The GC-CPI-MS/MS method showed good chromatographic resolution (peak half-widths between 3.1 to 5.3 s), acceptable linearity (coefficient of determination between 0.981 to 0.996), and repeatability (relative standard deviation (RSD%) between 5 to 18%). Limits of detection (LOD) were between 2 to 100 pg mL〈sup〉-1〈/sup〉 and limits of quantitation (LOQ) were between 0.05 to 2 ng mL〈sup〉-1〈/sup〉. In total, 15 steroids were quantified either as a free steroid or glucuronide conjugate from the urine of volunteers. The new CPI source design showed excellent sensitivity for analysis of steroids in complex biological samples.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 30 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Dmytro Iurashev, Susanne Schweiger, Alois Jungbauer, Jürgen Zanghellini〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Peak broadening in small columns is dominated by spreading in the extra column volume and not by hydrodynamic dispersion or mass transfer resistances. cfd permits to study the influence of these effects separately. Here, peak broadening of three single component solutes – silica nanoparticles, acetone, and lysozyme – was experimentally determined for two different columns (100 mm × 8 mm inner diameter and 10 mm × 5 mm inner diameter) under non-binding conditions. A mass transfer model between mobile and stationary phases as well as a hydrodynamic dispersion model were implemented in the computational fluid dynamics (cfd) environment STAR-CCM+®). The mass transfer model combines a model of external mass transfer with a model of pore diffusion. The model was validated with experiments performed on the larger column. We find that extra column volume plays an important role in peak broadening of the silica nanoparticles pulse in that column; it is less important for acetone and is weakly pronounced for lysozyme. Hydrodynamic dispersion plays the dominant role at low and medium flow rates for acetone because we are in a regime of 1–10 ReSc. Mass transfer is important for high flow rates of acetone and for all flow rates of lysozyme. Then, peak broadening was predicted in the smaller column with the packed bed parameters taken from larger column. The scalability of the prepacked columns is demonstrated for acetone and silica nanoparticles by excellent agreement with the experimental data. In contrast to the larger column, peak broadening in the smaller column is dominated by extra column volume for all solutes. Peak broadening of lysozyme is controlled only at high flow rates by mass transfer and overrides extra column volume and hydrodynamic dispersion. cfd simulations with implemented mass transfer models successfully model peak broadening in chromatography columns taking all broadening effects into consideration and therefore are a valuable tool for scale up and scale down. Our simulations underscore the importance of extra column volume.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 29 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Ning Zhang, Lishen Su, Suning Man, Xiaoyun Lei, Ting Huang, Chunling Zhu, Lan Zhang, Xiaoping Wu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A direct immersion solid-phase microextraction (DI-SPME) approach for gas chromatography-mass spectrometry (GC-MS) based on hybrid fiber coating of ionic liquid and polyhedral oligomeric silsesquioxane (POSS) is presented. To fabricate the task-specific coating for the enrichment of polycyclic aromatic hydrocarbons (PAHs), 1-butyl-3-vinylimidazolium bis[(trifluoromethyl)sulfonyl]imide (IL) and POSS were rapidly photoinitiated copolymerized within 5 min on a stainless steel fiber. The high efficient extraction of target analytes can be attributed to a combined result of multiple interactions including the strong C-F···H-C pseudohydrogen bonding, π-π stacking, hydrophobic force, and molecular sieve effect. A wide linear range (0.04 - 400 ng L〈sup〉-1〈/sup〉) with low detection limits in the range of 0.004 and 0.5 ng L〈sup〉-1〈/sup〉 were obtained for PAHs by GC-MS. The applicability of this coupling method was successfully demonstrated by the analysis of trace PAHs in real river water and soil samples, with satisfied recoveries (84.2-108.6%) and relative standard deviations (〈8.1%). Compared to the other commercial fiber-based SPME methods, the IL/POSS hybrid coating-based SPME is much cheaper, thermally stable and capable of eliminating possible deleterious effects as well.〈/p〉〈/div〉 〈h5〉Graphic abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0021967319303346-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 29 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Erin P. Shields, Stephen G. Weber〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Stationary phases that can withstand extremes of pH and temperature are needed to allow a single column to accommodate a wider set of solutes and separation criteria. We used a simple multi-step process using the thiol-yne reaction following the modification of the silica surface with a thiol-containing silane. The monomers 1,4-diethynylbenzene (DEB) and 1,6-hexanedithiol were used to create a crosslinked thiol-yne (CTY) stationary phase along the surface of the thiol functionalized silica. In the Tanaka test characterization, the CTY phase showed a low phase ratio, methylene selectivity typical of a reversed phase, and extremely high shape selectivity compared to commercial reversed phases. The hydrophobic subtraction model characterization showed a high positive steric resistance, a low hydrogen bond acidity, and a high cation-exchange capacity compared to most reversed phases. At pH 0.5 with an 85% aqueous mobile phase the phase showed no significant change over 114 h. With a 50% aqueous mobile phase the phase took four more days than a sterically protected C18 phase for the k’ to decline 25%. At pH 12.6, 50% aqueous mobile phase, a sterically protected C18 phase showed a 20% decrease in k’ and more than a 60% decrease in theoretical plates per meter in three hours. The CTY phase actually showed modest increases in k’ and theoretical plates per meter after three hours.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 30 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Juan Yang, Xin Dong, Yu-Han Hu, Qiu-Yan Wang, Shu-Ling Wang, Jun Cao, Hong-Hua Zhang〈/p〉 〈h5〉ABSTRACT〈/h5〉 〈div〉〈p〉A rapid and effective method was successfully established for the extraction and determination of chlorogenic acid, protocatechuic acid, malic acid, caffeic acid and gallic acid in fruit (chaenomeles speciosa) via matrix solid-phase dispersion (MSPD) microextraction combined with ultra-high performance liquid chromatography with quadrupole time-of-flight tandem mass spectrometry (UHPLC-Q-TOF/MS). Several major extraction parameters were investigated and optimized, such as the type of sorbent, the amount of sorbent, the grinding time, the type and concentration of the eluting solvent. The optimal extraction conditions were obtained by using 20 mg of calix[8]arene as dispersing adsorbent, selecting 60 s as the appropriate grinding time and applying 250 mM of [Domim]Br as eluent solvent. Moreover, the calibration curves of the analytes were in the range of 0.01–500 µg/mL with the determination coefficients (r〈sup〉2〈/sup〉) higher than 0.9995. The limits of detection and limits of quantification were in the range of 0.202–1.056 ng/mL and 0.674–3.521 ng/mL, respectively. The recoveries of the target compounds at two spiked levels were between 82.19 and 113.36%. Furthermore, this method had acceptable reproducibility (RSD ≤ 3.84%). The proposed approach combined the advantages of MSPD microextraction with UHPLC-Q-TOF/MS, and could be applicable for the analysis organic acids in fruit.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 29 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Jörgen Samuelsson, Finnur Freyr Eiriksson, Dennis Åsberg, Margrét Thorsteinsdóttir, Torgny Fornstedt〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉A strategy for determining a suitable solvent gradient 〈em〉in silico〈/em〉 in preparative peptide separations is presented. The strategy utilizes a machine-learning–based method, called ELUDE, for peptide retention time predictions based on the amino acid sequences of the peptides. A suitable gradient is calculated according to linear solvent strength theory by predicting the retention times of the peptides being purified at three different gradient slopes. The advantage of this strategy is that fewer experiments are needed to develop a purification method, making it useful for labs conducting many separations but with limited resources for method development.〈/p〉 〈p〉The preparative separation of met-enkephalin and leu-enkephalin was used as model solutes on two stationary phases: XBridge C18 and CSH C18. The ELUDE algorithm contains a support vector regression and is pre-trained, meaning that only 10–50 peptides are needed to calibrate a model for a certain stationary phase and gradient. The calibration is done once and the model can then be used for new peptides similar in size to those in the calibration set. We found that the accuracy of the retention time predictions is good enough to usefully estimate a suitable gradient and that it was possible to compare the selectivity on different stationary phases 〈em〉in silico〈/em〉. The absolute relative errors in retention time for the predicted gradients were 4.2% and 3.7% for met-enkephalin and leu-enkephalin, respectively, on the XBridge C18 column and 2.0% and 2.8% on the CSH C18 column. The predicted retention times were also used as initial values for adsorption isotherm parameter determination, facilitating the numerical calculation of overloaded elution profiles. Changing the trifluoroacetic acid (TFA) concentration from 0.05% to 0.15% in the eluent did not seriously affect the error in the retention time predictions for the XBridge C18 column, an increase of 1.0 min (in retention factor, 1.3). For the CSH C18 column the error was, on average, 2.6 times larger. This indicates that the model needs to be recalibrated when changing the TFA concentration for the CSH column.〈/p〉 〈p〉Studying possible scale-up complications from UHPLC to HPLC such as pressure, viscous heating (i.e., temperature gradients), and stationary-phase properties (e.g., packing heterogeneity and surface chemistry) revealed that all these factors were minor to negligible. The pressure effect had the largest effect on the retention, but increased retention by only 3%. In the presented case, method development can therefore proceed using UHPLC and then be robustly transferred to HPLC.〈/p〉 〈/div〉

Description: 〈p〉Publication date: Available online 27 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Yiwen Zhang, Xinyan Lv, Ran Liu, Mingyang Zhang, Haopeng Liu, Hao Gao, Qian Zhang, Huarong Xu, Qing Li, Kaishun Bi〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Traditional Chinese Medicines (TCMs) have been widely used in orient countries for thousands of years, while their inconsistent quality and therapy issues have become increasingly serious as a result of the absence of effective methods for quality control. Therefore, it is necessary to develop a novel and specific evaluation system for TCMs’ quality involved with not only composition but also bioactivity. In this study, we used 〈em〉Schisandra chinensis (Turcz.)〈/em〉 Baill as an example and developed a novel integrated approach involved with various chemical analysis and data processing methods to explore its quality marker (Q-marker) underlying its anti-depressive effects. First, six bioactive lignans were identified and semi-quantified in rat brain samples via high resolution mass spectrometry. Then, the bioinformation analysis showed that all the six bioactive components could modulate various diseases relative to noradrenergic, dopaminergic and serotonergic pathways. Thus, the monoaminergic metabolites contained in these three pathways were selected to screen potential biomarkers of depression treated by S. chinensis based on target metabolomics using a rapid HPLC-MS/MS method. Finally, the correlation analysis between the six components and potential biomarkers was employed to uncover the Q-markers of S. chinensis. It is suggested that schisandrol A, schisandrin A, schisandrin C and gomisin N could be determined as Q-markers for S. chinensis. Thus, the integrated approach describing here for discovering Q-markers was expected to offer an alternative quality assessment strategy of herbal medicines for the first time.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 28 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Thomas Avery Garran, Ruifeng Ji, Jin-Long Chen, Dongmei Xie, Lanping Guo, Lu-Qi Huang, Chang-Jiang-Sheng Lai〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The isomer structural discrimination is a significant challenge in metabolome analysis based on ultrahigh performance liquid chromatography tandem high-resolution mass spectrometry (UHPLC-HRMS). In this study, a new discriminating metabolite isomerism strategy is proposed to elucidate the metabolome, especially the isomers, of 〈em〉Leonurus japonicus〈/em〉 and 〈em〉Leonurus cardiaca〈/em〉. This strategy consists of three steps. First, the metabolite biosynthesis pathways are constructed based on a home-built compound database to rapidly profile the compounds of interest using the multiple diagnostic product ions (DPIs) screening analysis and binary comparison based on SUMPRODUCT function. Second, the fragmentation patterns (〈em〉e.g.〈/em〉 the high-resolution DPIs, DPI ratios) and chromatographic elution order are defined based on scattered reference chromatographic and mass spectrometry data, calculated lipophilicity parameters, molecular hydrogen bond analysis, and chemical reference standards. Finally, all discovered isomerisms are mapped with the defined applicable rules and the isomers are identified conveniently. Using this strategy, a total of 257 compounds were tentatively characterized, including 212 potential novel compounds and 67 pairs of 〈em〉cis〈/em〉-, 〈em〉trans〈/em〉-, and positional isomers of flavonoids, phenylethanoid glycosides, glucaric acids, novel quinic acids, and esters of fatty acids. Moreover, 56 characteristic markers were identified to discriminate these two herbal medicines. This strategy may significantly improve the efficiency and reliability of identifying isomers found in metabolite biosynthesis pathways.〈/p〉〈/div〉

Description: 〈p〉Publication date: 22 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1587〈/p〉 〈p〉Author(s): Meiru Pan, Ping Xiang, Zhiguo Yu, Yunli Zhao, Hui Yan〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The screening analysis for drugs and poisons always symbolizes the capabilities of a forensic laboratory. Due to the rapid emergence of new compounds in clinical and forensic intoxication cases, sensitive and specific methods are necessary for the screening of wide range of target compounds. A novel high-throughput screening method has been developed for the toxicological analysis of 288 drugs and poisons in human blood using Orbitrap technology with gas chromatography-high resolution mass spectrometry (GC-HRMS). This method allows for the fast detection and identification of high-throughput forensically important drugs and poisons, e.g., drugs of abuse (cocaine, amphetamines, synthetic cannabinoids, opiates, hallucinogen), sedative-hypnotics, antidepressants, non-steroidal anti-inflammatory drugs, pesticides (acaricides, fungicides, insecticides, nematicides), and cardiovascular agents in one single GC-Q Exactive run. After a simple extraction with ethyl ether and buffer, following centrifugation, the supernatant was injected into the system. For detection, spiked blood samples were analyzed by Orbitrap-GC-HRMS using an electrospray ionization in full scan mode with a scan range from 40 to 650 (〈em〉m/z〈/em〉). The identification of drugs and poisons in the samples was carried out by searching the accurate molecular mass of characteristic fragment ions, ion rations and retention time (RT) against the in-house library that we developed with 70 ev electron energy. The limit of detection (LOD) for most compounds (249 in a total of 288 compounds) was below 100 ng/mL. For selectivity, no substances have been identified in drug-free blood samples from six different sources, and the method was suitable for the recovery and the carryover. The coefficient of variation (CV) of the RTs was below 0.99% in all reproducibility experiments. Mass accuracy was always better than 3 ppm, corresponding to a maximum mass error of 1.04 millimass units (mmu). The developed method was applied to 136 real samples from forensic cases, demonstrating its suitability for the sensitive and fast screening of high-throughput drugs in human blood samples.〈/p〉〈/div〉

Description: 〈p〉Publication date: 22 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1587〈/p〉 〈p〉Author(s): Xiaosheng Guan, Zhijun Zhao, Siyi Cai, Shuxiao Wang, Hua Lu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A single-channel comprehensive two-dimensional gas chromatography-quadrupole mass spectrometry (GCxGC-qMS) system was developed using a recently introduced solid-state thermal modulator. By modulation on a special column, extremely light hydrocarbons down to C2 can be successfully modulated without use of any cryogens. Paired with a polar secondary dimension column, a hybrid primary dimension column was developed to provide complete two-dimensional separation of all target volatile organic compounds (VOCs) from C2 to C12. This single-channel GCxGC-qMS system is used to analyze VOC standards containing 57 PAMS and 64 TO-15 gas mixtures, as well as real-world samples. This study demonstrates that a low resource GCxGC-qMS system may serve as a feasible tool for routine VOCs monitoring.〈/p〉〈/div〉

Description: 〈p〉Publication date: 22 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1587〈/p〉 〈p〉Author(s): Melissa N. Dunkle, Pascal Pijcke, Bill Winniford, George Bellos〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Hydrocarbons analysis is important in the oil and gas industry, as stream composition has a strong impact on plant operations. The composition of hydrocarbon streams vary across a plant, which makes the selection of analytical methods challenging. Traditional methods for the evaluation of liquid hydrocarbon streams include the Detailed Hydrocarbon Analysis (DHA); however, non-traditional methods, such as comprehensive gas chromatography (GCxGC), are also utilized in the chemical industry, including Dow. This work details a comparison of analytical techniques available for such analyses, specifically, DHA and GCxGC compared to the recently introduced GC-Vacuum Ultra Violet (GC-VUV) system. Numerous liquid hydrocarbon streams were blended together to generate a composite and extensive matrix in terms of composition. Paraffin, isoparaffin, olefin, naphthene, and aromatic (PIONA) results are presented for the three techniques. All of those methods obtained relative standard deviations lower than 1.3% for five injections a day for three days. Standard addition curves were utilized to accurately quantify specific compounds in a liquid hydrocarbon stream, and these results were compared to the GC-VUV PIONA+ and DHA quantification procedures.〈/p〉〈/div〉

Description: 〈p〉Publication date: 22 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1587〈/p〉 〈p〉Author(s): Ursula Simon, Simone Dimartino〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Monolithic adsorbers with anion exchange (AEX) properties have been 3D printed in an easy one-step process, i.e. not requiring post-functionalization to introduce the AEX ligands. The adsorber, 3D printed using a commercial digital light processing (DLP) printer, was obtained by copolymerisation of a bifunctional monomer bearing a positively charged quaternary amine as well as an acrylate group, with the biocompatible crosslinker polyethylene glycol diacrylate (PEGDA). To increase the surface area, polyethylene glycol was introduced into the material formulation as pore forming agent. The influence of photoinitiator (Omnirad 819) and photoabsorber (Reactive Orange 16, RO16) concentration was investigated in order to optimize printing resolution, allowing to reliably 3D print features as small as 200 μm and of highly complex Schoen Gyroids. Protein binding was measured on AEX adsorbers with a range of ligand densities (0.00, 2.03, 2.60 and 3.18 mmol/mL) using bovine serum albumin (BSA) and c-phycocyanin (CPC) as model proteins. The highest equilibrium binding capacity was found for the material presenting the lowest ligand density analysed (2.03 mmol/mL), adsorbing 73.7 ± 5.9 mg/mL and 38.0 ± 2.2 mg/mL of BSA and CPC, respectively. This novel 3D printed material displayed binding capacities in par or even higher than commercially available chromatographic resins. We expect that the herein presented approach of using bifunctional monomers, bearing commonly used chromatography ligands, will help overcome the material limitations currently refraining 3D printing applications in separation sciences.〈/p〉〈/div〉

Description: 〈p〉Publication date: 25 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1585〈/p〉 〈p〉Author(s): Bibiana da Silva, Luciano Valdomiro Gonzaga, Roseane Fett, Ana Carolina Oliveira Costa〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Honeydew honeys have been under-evaluated about their major phenolic compounds, especially 〈em〉Mimosa scabrella〈/em〉 Bentham (bracatinga) honeydew honey. In this work, a fast and robust chromatographic method was optimized for simultaneous separation and quantification by HPLC/DAD of 18 phenolic compounds detected in bracatinga honeydew honey. A simplex-centroid design, central composite rotatable design and response surface-desirability function simultaneous optimization of Derringer and Suich were used, evaluating the mobile phase composition, flow rate and oven temperature to separate all the peaks. These multivariate procedures were efficient in determining the optimal separation conditions, using peak pair resolutions and run time as responses. The 18 peaks were separated in 25 min and the mobile phase gradient started with 1.6% MeOH, 3.3% ACN, 1.0% THF and 94.1% formic acid 0.1% changing to 10.0% MeOH, 33.3% ACN, 6.0% THF and 50.7% formic acid 0.1%, oven temperature of 33 °C and flow rate of 0.73 mL min〈sup〉−1〈/sup〉. The method was validated according to Eurachem guidelines and considered accurate and robust. It was applied to 18 bracatinga honeydew honey samples in which 9 phenolic compounds were identified and quantified.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 3 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Meng Chen, Hua Bai, Junfeng Zhai, Xianshuang Meng, Xiangyu Guo, Chun Wang, Penglong Wang, Haimin Lei, Zengyuan Niu, Qiang Ma〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉An analytical methodology for comprehensive screening of 63 coloring agents of great concern for regulatory control in cosmetics has been established using ultra-high-performance liquid chromatography (UHPLC) coupled with quadrupole-Orbitrap high-resolution mass spectrometry (Q-Orbitrap HRMS). An effective, rapid, and simple sample pretreatment protocol with low sample and reagent consumption was developed based on matrix solid-phase dispersion (MSPD). The selection of the most suitable extraction conditions was made using statistical tools of factorial multifactor experimental design and analysis of variance (ANOVA). In the final conditions, 0.1 g of cosmetic sample was blended with 0.3 g of anhydrous sodium sulfate and 0.4 g of sand, and the MSPD column was eluted with 2 mL of methanol. The extract was analyzed by UHPLC-Q-Orbitrap HRMS under synchronous full-scan MS and data-dependent MS/MS (full-scan MS〈sup〉1〈/sup〉/dd-MS〈sup〉2〈/sup〉) acquisition mode. The mass resolution was set to 70,000 FWHM (full width at half maximum) for full-scan MS〈sup〉1〈/sup〉 and 17,500 FWHM for dd-MS〈sup〉2〈/sup〉 stage with the experimentally measured mass deviations of less than 3 ppm (parts per million) for quasi-molecular ions and 5 ppm for characteristic fragment ions for each individual analyte. An accurate-mass database and a mass spectral library were built in house for searching the 63 target compounds. Broad screening was conducted by comparing the experimentally measured exact mass of precursor and fragment ions, retention time, isotopic pattern, and ionic ratio with the accurate-mass database and by matching the acquired MS/MS spectra against the mass spectral library. Method performance was evaluated in terms of limits of detection (LODs), limits of quantitation (LOQs), linearity, precision, recovery, and matrix effect. The UHPLC-Q-Orbitrap HRMS approach was applied for the simultaneous analysis of 63 target coloring agents in 69 genuine cosmetic samples. Eleven legally prohibited coloring agents were detected in 26 cosmetic samples in total. The proposed method exhibited great potential for high-throughput, sensitive, and reliable screening of multi-class coloring agent substances in cosmetics.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 3 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Yuanhong Chen, Kunpeng Chang, Xi Xie, Xiaohua Liu, Mengya Jia, Lijuan Nie, Haixing Li, Shuixing Wang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉γ-aminobutyric acid (GABA) is a key physiologically active molecule in organisms. Separation of glutamate from its decarboxylated product GABA has been vigorously pursued. The interaction between these two compounds severely hindered their disassociation. Herein, we present a new strategy, termed zinc acetate-assisted differential precipitation/dissolution (ZA-DPD), for the removal of glutamate by step by step recovering pure GABA solution and discarding pure glutamate pellet, essentially attributed to the use of two core reagents (zinc acetate-assisted glutamate-precipitating reagent, and glutamate-rejecting reagent). In each precipitation, the zinc acetate-assisted glutamate-precipitating reagent guaranteed most GABA still soluble although the rest co-precipitated with glutamate; in the coupled dissolution, the co-precipitated GABA was fully dissolved with or without (in the case of glutamate-rejecting reagent used in the final dissolution) co-dissolution of glutamate. The process was repeated twice until glutamate was thoroughly removed. An accurate quantitative method coupling ZA-DPD with colorimetry was thereafter established for the determination of GABA. This study may facilitate the areas associated with GABA or glutamate.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 2 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): María Teresa Fernández-del-Campo-García, Ana María Casas-Ferreira, Encarnación Rodríguez-Gonzalo, Bernardo Moreno-Cordero, José Luis Pérez-Pavón〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this paper, a high-throughput approach is proposed for the sensitive screening and the confirmatory analysis of polar compounds in saliva using a two-step approach based on a liquid chromatographic system coupled to a triple quadrupole mass spectrometer. A reversed-phase chromatographic column was used in both steps and changes in the composition of the mobile phase allowed the screening and the confirmatory analyses to be performed with the same instrumental configuration. The proposed strategy has been tested for the determination of a multiclass group of polar endogenous compounds (creatinine, polyamines and amino acids) in saliva samples. The validation of the entire procedure showed consistent results for all the compounds in both steps. Repeatability and reproducibility were evaluated for both procedures, with values below 8% in the case of repeatability and 17% in the case of reproducibility. The instrumental limits of detection were found to be between 1.22 × 10〈sup〉−3〈/sup〉 and 46.1 × 10〈sup〉−3〈/sup〉 mg/L for creatinine and lysine, respectively, and accuracy of the method was evaluated in terms of apparent recoveries and values were found to be between 80 and 127%. Matrix effects were evaluated and it was found that the analytical outcome was influenced by the matrix of the sample. Thus, a one-point standard addition method was used for quantification. The optimized two-step procedure was applied to saliva samples from apparent healthy volunteers. Overall, satisfactory results were obtained in both steps, demonstrating its applicability for quantitative analysis of polar endogenous compounds in this kind of matrices.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 2 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Zuzana Bílková, Marie Adámková, Tomáš Albrecht, Zdeněk Šimek〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Feathers gradually accumulate hormones and reflect long-term average plasma steroid levels during their growth. Feather hormone levels thus provide for the measurement of plasma hormones concentrations integrated over a period of several days or weeks. In this study, we focused on the development of a method to determine testosterone (TEST) and corticosterone (CORT) levels in extracts from feathers of small bodied birds with a limited amount of feathers available per individual. For this purpose, the method had to be verified for a small weight of samples. The present study describes the effect of the conditions of sample preparation and keto-derivatisation on the sensitivity of the LC–ESI–MS/MS analysis of TEST and CORT. Generally, chemical derivatization improves the sensitivity and selectivity of LC–MS/MS analysis. It can be used particularly in situations when the total amount of collected sample is limited (such as in our studies). Both the conditions of feather sample preparation (the selection of the extraction solvent, the time of extraction, and the conditions of solid phase extraction) and the reaction conditions affecting the formation of keto-derivatives (such as reaction temperature and reaction time) were tested. Methanol as the extraction solvent, 8 h as the extraction time, 50 °C as the reaction temperature of derivatization, and 90 min as the reaction time of derivatization are the most suitable conditions in terms of achieving a high sensitivity of analyses. Calibration curves are linear, at least in the range 25–2500 pg mL〈sup〉−1〈/sup〉, which is usually found in feather extracts. The limit of detection (LOD) for TEST and CORT was 1.0 and 0.3 pg per mL, respectively. The limit of quantification (LOQ) for TEST and CORT was 3.3 and 1.0 pg per mL, respectively. The optimized procedure was successfully applied for the analysis of TEST and CORT in real feather samples. The method could be used in a variety of research direction including wildlife, agricultural or veterinary studies.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 30 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Dasheng Lu, Liming Xue, Chao Feng, Yu’e Jin, Chunhua Wu, Cen Xie, Frank J. Gonzalez, Guoquan Wang, Zhijun Zhou〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Simple metabolome and lipidome sample preparation procedures involving two successive extractions using small pieces of tissue, and a subsequent metabolite identification (MetID) strategy were developed. The sample preparation can significantly circumvent incomplete analysis due to insufficient amounts of tissue as a result of splitting into several aliquots for multiple measurements, with advantages over the similar previously reported methods in metabolite coverage, extraction efficiency, method robustness and friendly experimental operation. A MetID strategy, based on the integration of MS information mining (including adduct ions, in-source CID, MS information from both ESI (+) and ESI (-), characteristic fragmentation ions (CFIs), constant neutral losses (CNLs) and multimers) and 〈em〉in silico〈/em〉 MS simulation, was demonstrated. A large number of adduct ions (83 features), in-source CID (123 features), ESI (+/-) ionization (20 features), CFIs& CNLs (more than 120 features) and multimers (17 features) were mined by manually or 〈em〉in silico〈/em〉 recognition/filtering, which provide the most suspicious structures for subsequent 〈em〉in silico〈/em〉 MS simulation. The unknown features presented the same score distribution as the known (83 features) features with scores ≥25% (geomean score: 52%) and with satisfactory match for the main ions of interest. The MS/MS noise and fragment ions of coeluted quasi-molecular ions of interest are the main reason for the low score in the simulation. Manual check/evaluation is always suggested for the simulation with a score less than 50%. This strategy presents satisfactory performance with 2.5 times more metabolites structurally characterized compared with that of the traditional method based on accurate-mass-based MS and MS/MS library matching. This strategy would be useful for potentially identifying metabolites without available MS/MS information in the library.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 30 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Li Xie, Jingjing Huang, Qing Han, Yuan Song, Ping Liu, Xuejun Kang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper put forward a prospective pre-cleanup method of packed-fiber solid phase extraction by using Polypyrrole (Ppy) electrospun nanofibers as the sorbent to simultaneously extract three water-soluble vitamins (i.e., folic acid, cyanocobalamin and riboflavin) in human urine. Primary extraction of target analytes was carried out by loading samples onto the column along with diphenylboronic acid 2-aminoethylester (DPBA) reagent, and then the column should be rinsed with DPBA solution for three times before eluting. The DPBA was innovatively applied as complexing reagent to retain as much of three analytes as possible on the column based on the multi interaction between three vitamins and the boronate affinity reagent, thus improving hydrophobicity of targets and adsorption efficiency through loading and rinsing steps. Under optimized conditions, sample concentration factor was five times with small amount of organic solvent consumed and recoveries between 84.9% to 125.4%, and the lowest detection limit (LOD) between 0.020 to 0.041 μg/mL were achieved. Finally, the urine samples from a group of healthy children were processed with the optimized method. It proved that the proposed method is applicable in the determination of urinary B-vitamins in big samples of people.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 30 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Hossein Abdolmohammad-Zadeh, Abbasali Zamani, Zahra Shamsi〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A novel magnetic solid-phase extraction technique based on a ternary nano-composite, magnetite/reduced graphene oxide/silver, as a nano-sorbent was developed for simultaneous extraction/preconcentration and measurement of morphine and codeine in biological samples by high-performance liquid chromatography. The magnetic ternary nano-composite was synthesized and its functional groups, morphological structure, and magnetic properties were characterized by field emission scanning electron microscopy, vibrating sample magnetometer, powder X-ray diffraction, energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy. The optimizing of the significant variables affecting the extraction process was evaluated by a response surface methodology. In the optimized conditions, the constructed calibration curves for morphine and codeine are linear in the range of 0.01–10 μg L〈sup〉−1〈/sup〉 with correlation coefficients of 0.9983 and 0.9976, respectively. The detection limit and enrichment factor for morphine and codeine are 1.8 ng L〈sup〉−1〈/sup〉, 1000 and 2.1 ng L〈sup〉−1〈/sup〉, 1000, respectively. The presented technique was employed for the monitoring of morphine and codeine in numerous blood and urine samples with relative recoveries between 97.0 and 102.5%, and relative standard deviations of 1.02–5.10% for the spiked samples.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 30 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Tomoyuki Tsuchiyama, Miki Katsuhara, Jun Sugiura, Masahiro Nakajima, Atsushi Yamamoto〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In the analysis of pesticides performed with gas chromatography, the quantitative performance of measurements can be severely compromised by phenomena known as matrix effects. In seeking a solution to the problem of matrix effects, the application of a modifier gas generator (MGG) was investigated in this study, together with analyte protectants and multiple internal standards. Ethylene glycol (EG) was used as modifier gas and matrix effects in GC〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉MS analysis were then evaluated by using the extracts of various food commodities. MGG was used in combination with other known methods of matrix effect compensation and its performance in reducing matrix effects tested. We have found that by combining MGG with conventional analyte protectants, matrix effects were substantially reduced for most of pesticides. Use of EG was especially effective for organophosphate pesticides and those with amino groups. Using this approach, the shortcomings of conventional analyte protectants were remedied. Although neither EG nor analyte protectants could sufficiently reduce the matrix effects for certain classes of pesticides, this limitation could be overcome with the use of multiple internal standards (IS) in the analysis. Finally, it was shown that the method we developed could achieve better analytical performance than the matrix-matched calibration method. Our method was robust with respect to the variation of food matrix components, so its application to real-world analyses would be practical and promising.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 28 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Patrícia P.K.G. Costa, Thaís D. Mendes, Thaís F.C. Salum, Thályta F. Pacheco, Samira C. Braga, João Ricardo M. de Almeida, Sílvia B. Gonçalves, Mônica C.T. Damaso, Clenilson M. Rodrigues〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The recent increase in the production of crude glycerin through the manufacture of biodiesel has imputed a commercial issue, the excess of this raw material in the market and its constant devaluation, which resulted in the need for new technologies for its use. Crude glycerin can be used in biotechnological processes for the production of high value-added compounds. This study presents novel, simple and fast methods based on ultra-high performance liquid chromatography (UHPLC) using evaporative light scattering detection (ELSD) for simultaneous analysis of ten sugar alcohols with a hydrophilic interaction chromatography (HILIC) column. The selected compounds and their possible stereoisomers have major commercial importance and they can be obtained by biotechnological routes. Under optimized conditions, threitol, erythritol, adonitol, xylitol, arabitol, iditol, sorbitol, mannitol, dulcitol and volemitol can be analyzed simultaneously within 15.0 min. The use of different column temperatures was a key parameter to reach the selectivity during the separation of some stereoisomers. Regression equations revealed a good linear relationship (R 〉 0.995) over the range from 50.0 to 800.0 ng. Limits of detection (LOD) and quantification (LOQ) ranged from 30.0 to 45.0 ng and 50.0–75.0 ng, respectively. The HILIC-UHPLC-ELSD methods showed good precision with low coefficient of variation (CV%) for the intra- and inter-assays experiments (≤ 5.1%) and high repeatability in terms of retention times for each analyte (≤ 0.5%). The accuracy was confirmed with an average recovery ranging from 92.3 to 107.3%. The developed methods employ an analytical technique more accessible and suitable for routine analyzes and have shown to be suitable for simultaneous analysis of sugar alcohols present in crude bioconverted glycerin samples using different classes of microorganisms.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 26 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Josephine S. Lübeck, Linus M.V. Malmquist, Jan H. Christensen〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Unconventional oil feeds can be rich in oxygenated organic compounds that will negatively affect the fuel properties if they are not removed during refining. In this study, supercritical fluid chromatography (SFC) was utilised for the combined analysis of polycyclic aromatic hydrocarbons (PAHs) and oxygenated polycyclic aromatic compounds (OPACs). One objective was to chromatographically separate PAHs from OPACs; another to reach a high peak capacity, improved peak shapes and high signal-to-noise ratios (S/N) for OPACs. These objectives were set to establish a non-target analysis method for oxygenated compounds in unconventional oils by SFC hyphenated to a UV detector and a quadrupole time-of-flight mass spectrometer (QTOF-MS) with negative electrospray ionisation (ESI〈sup〉−〈/sup〉). Highest peak capacities were observed with a 2-picolylamine column with methanol as modifier, however, a better resolution and S/N were obtained with ethanol and 0.1% formic acid. The elution order for OPACs on all columns followed mainly the polarity of the analytes: furans 〈 aldehydes ≤ ketones 〈 phenols ≤ carboxylic acids. Best separation between PAHs and OPACs was achieved with the ethylene-bridged silica column. The optimised SFC-UV-ESI〈sup〉−〈/sup〉-QTOF-MS method was tested on a coal tar middle distillate and a pyrolysis oil where a number of homologous series (e.g. hydroxy-naphthalenes and –benzaldehydes) was tentatively identified.〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1588〈/p〉 〈p〉Author(s): Abdeljalil Akchich, Julie Charton, Emmanuelle Lipka〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Chromatographic separation of compounds with more than one chiral center is challenging, requiring high resolution methods. Owing to the low viscosity of the mobile phase, Supercritical Fluid Chromatography (SFC) enables the tandem coupling of columns which increases resolution compared over a single column and can be effective in resolving stereoisomers. Enantioseparation of a dihydropyridone derivative with two chiral centers, synthetic API, was here studied using SFC. Six polysaccharide-based, chiral stationary phases with a mobile phase consisting of a carbon dioxide/methanol mixture (80:20 v:v) were investigated at 40 °C and a flow-rate of 3 mL/min, but only incomplete separation of the four expected stereoisomers was observed. We then examined different combinations of columns in tandem. It was found that, among the thirteen successful tandems, the OJ-H//AD-H system gave complete baseline resolution of the four stereoisomers with 4.98, 5.63, 6.06 and 6.89 as retention times and 2.97, 1.83 and 3.54 as resolution values. The conditions were further optimized to obtain the best resolution in the shortest elution time. The best conditions were transposed to semi-preparative scale to obtain the pure isomers, with yield increased by using stacked injections. The four fractions allowed the attribution of elution order on all tandem performed previously. The column order itself had no impact on the stereoisomeric elution order but the type of stationary phase and column order strongly influenced the resolution. In parallel, a previously reported mathematical model was used to predict the retention times of the four stereoisomers on each of the six polysaccharide-based, chiral stationary phase column tandems. This mathematical model was successfully applied to predict separation the dihydropyridone derivative’s isomers on two columns with chlorinated stationary phases.〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1588〈/p〉 〈p〉Author(s): Yajing Jian, Jiali Deng, Hongbin Zhou, Jing Cheng〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A novel solid phase microextraction fiber named graphene oxide incorporated poly acrylamide-ethylene glycol dimethacrylate (GO-poly AM-EDGMA) monolithic fiber has been successfully prepared in a fused silica capillary tube (250 μm, i.d.) via thermally initiated polymerization using acrylamide (AM) as the monomer, ethylene glycol dimethacrylate (EGDMA) as the crosslinker, dimethylformamide dispersed by GO as porogens, and then obtained by removing 1 cm wall from one end of the fused silica capillary tube. The fiber has large surface area (536 m〈sup〉2〈/sup〉 g〈sup〉−1〈/sup〉), pore capacity (0.694 cm〈sup〉3〈/sup〉 g〈sup〉−1〈/sup〉) good thermal stability (up to 320 ℃), long service life and good reproducibility (RSD ＜5% throughout 110 times) which facilitated for high throughput headspace solid phase microextraction (HS-SPME) coupled to gas chromatograph (GC) analysis. The HS-SPME/GC method using the new fiber was evaluated by the determination of five organophosphate esters (OPEs) in soil samples coupled to flame photometric detector (FPD). The proposed HS-SPME-GC/FPD method yielded satisfactory limits of quantification (0.03 ng g〈sup〉−1〈/sup〉∼0.24 ng g〈sup〉−1〈/sup〉); linearity (≥0.99), good intra- and inter-day precision expressed as relative standard deviations for a single fiber were in the range of 5.2–9.0% and 4.8–9.0%, respectively, and fiber-to-fiber reproducibility was in the range of 5.9–9.7%. The method was applied for the analysis of OPEs in environmental soil samples and the relative recoveries were found to be in the range from 80.1 to 105.6%. Based on these features, the new fiber has great potential for widespread use as a high throughput trace analysis tool.〈/p〉〈/div〉

Description: 〈p〉Publication date: 8 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1586〈/p〉 〈p〉Author(s): Shiuhang Henry Yip, Dauh-Rurng Wu, Peng Li, Dawn Sun, Scott H. Watterson, Rulin Zhao, Joseph Tino, Arvind Mathur〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Bruton's tyrosine kinase (BTK) plays an essential role in multiple cell types responsible for numerous autoimmune diseases, thus inhibition of BTK is anticipated to provide an effective strategy for the clinical treatment of autoimmune diseases. Preparative-scale super/subcritical fluid chromatography (SFC) separation methods for four groups of highly potent and selective BTK inhibitor atropisomers were successfully developed. Depending on the rotation barrier around the chiral axis, the compounds were prepared as a single stereochemically stable atropisomer or as an atropisomeric mixture. Among the four, compound 2 with one rotationally stable atropisomeric center (carbazole/quinazolinedione based) was resolved as a mixture of two atropisomers, while compound 3 (carbazole-chlorine/quinazolinedione based) and 4 (tetrahydrocarbazole-fluorine/quinazolinedione based) with two rotationally stable atropisomeric centers were resolved into a single stable atropisomer. This article discusses the challenges and strategies in preparing large quantities of these atropisomeric active pharmaceutical ingredients (APIs) in support of the BTK program discovery efforts.〈/p〉〈/div〉

Description: 〈p〉Publication date: 22 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1587〈/p〉 〈p〉Author(s): Li Zhou, Jin-Di Xu, Shan-Shan Zhou, He Zhu, Ming Kong, Hong Shen, Ye-Ting Zou, Long-Jie Cong, Jun Xu, Song-Lin Li〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In metabolomics studies, metabolic pathway recognition (MPR) is performed by software tools to screen out the significant pathways disturbed by diseases or reinstated by drugs. To achieve MPR, the significantly changed metabolites determined in different biospecimens (〈em〉e.g.〈/em〉 plasma and urine) are analyzed either independently (metabolites from each biospecimen as a dataset) or integratively (metabolites from all biospecimens as a dataset). However, whether the choice of these two processing approaches affects the results of MPR remains unknown. In this study, this issue was addressed by selecting evaluation of the effects of the herbal medicine Rehmanniae Radix (RR) on anemia and adrenal fatigue by UPLC-QTOF-MS/MS-based metabolomics as an example. The significant pathways disturbed by the modeling of anemia and adrenal fatigue and those reinstated by treatments with raw and processed RR were recognized using MetPA software tool (〈em〉MetaboAnalyst 3.0〈/em〉), and compared by independent and integrative processing of the significantly changed metabolites determined in plasma and urine. The results showed that the two processing approaches could yield different impact values of pathways and thereby recognize different significant pathways. The differences appear to happen more easily when metabolites from different biospecimens shared the same metabolic pathway. Such pathway could be recognized as a significant pathway by integrative processing but could be excluded by independent processing due to the converged and dispersed importance contributions of the involved metabolites to MPR in the two processing approaches. This issue should concern researchers because MPR is crucial not only to understanding metabolomics data but also to guiding subsequent mechanistic research.〈/p〉〈/div〉

Description: 〈p〉Publication date: 22 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1587〈/p〉 〈p〉Author(s): Joanna Giebułtowicz, Monika Sobiech, Monika Rużycka, Piotr Luliński〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this paper, we proposed an innovative hydrophilic interaction dispersive solid-phase extraction (HI-d-SPE) protocol suitable for the isolation of the potential cyanide intoxication marker, 2-aminothiazoline-4-carboxylic acid (ATCA), from such complicated matrix as post-mortem blood. To create an optimal HI-d-SPE protocol, two sorbents were used: a molecularly imprinted polymer (MIP) and commercially available Oasis-MCX〈sup〉®〈/sup〉. The latter sorbent was identified as more recovery-efficient with higher clean-up abilities in a carefully optimized process. Computational analysis was employed to provide insight into the adsorption mechanism of the two selected sorbents. The theoretical results were in agreement with the experiment regarding the efficiency of the sorbent. HI-d-SPE was successfully applied to the analysis of ATCA in 20 post-mortem blood samples using LC–MS/MS. The analytical performance of the method was finally compared to prior existing methods, in turn revealing its superiority.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 31 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Shuai-Shuai Chi, Chao Peng, Yao-Han Lan, Hui-Yuan Yang, Xin-Zhu Chen, Luo-Bing Han, Chao Zheng, Lin-Yi Dong, Xian-Hua Wang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Boronate affinity materials are usually used for selective enrichment of 〈em〉cis〈/em〉-diol-containing compounds, mainly based on formation of pH-dependent cyclic ester between 〈em〉cis〈/em〉-diol and boronic acid. Recently, B–N coordination, or combined with hydrogen-bonding interaction, was employed as primary interaction for the extraction of nitrogen-containing compounds. However, there are no reports about the combination of hydrophobic (or π-π) interaction and B–N coordination for the extraction. Here, we prepared a novel hydrophobic phenyl-boronic acid polymer (PBAP) through initiator-free ring-opening polymerization. The adsorption experiment indicated that the PBAP could combine hydrophobic (or π-π) interaction and B–N coordination to enhance their adsorption capacity toward hydrophobic and nitrogen-containing compounds, for example sulfamethoxazole (SMX) and trimethoprim (TMP). In addition, the PBAP monolith synthesized in pipette tip was used as solid phase microextraction (SPME) sorbent with combination of ultra high performance liquid chromatography to extract and monitor SMX and TMP from animal-originated foodstuffs. The proposed method exhibited low limit of quantitation as 5.0 and 1.0 ng mL〈sup〉−1〈/sup〉 for SMX and TMP, respectively. The recoveries at three spiked levels were between 92.4% to 100.5% for SMX, and 92.7% to 102.6% for TMP, with intra-day and inter-day relative standard deviations no more than 5.3% and 8.6%, respectively. These results well demonstrated that the combination of hydrophobic (or π-π) interaction and B–N coordination played an important role in the extraction of hydrophobic and nitrogen-containing compounds.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 28 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Janice Z. Francesquett, Tiele M. Rizzetti, Tito R.S. Cadaval, Osmar D. Prestes, Martha B. Adaime, Renato Zanella〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, a modified Quick Polar Pesticides (QuPPe) method, optimized by a central composite design, was developed to determine quaternary ammonium pesticides (QUATs) residues in barley and wheat by ultra-high-performance liquid chromatographic tandem mass spectrometry (UHPLC-MS/MS) using a hydrophilic interaction chromatography (HILIC) column. Considering the high polarity of these compounds, special conditions of sample preparation and analysis are required. Different mobile phases, extraction procedure and clean-up were evaluated. An isocratic elution with aqueous solution of ammonium formate 60 mmol L〈sup〉−1〈/sup〉 (pH 3.7) and acetonitrile, 40:60 (v/v), was selected. Water and acidified methanol as extraction solvent, without heating, and a clean-up with dichloromethane, chitosan and acetonitrile presented good results. The validated method presented satisfactory selectivity, linearity, matrix effect, trueness and precision, providing recoveries from 93 to 110% with RSD 〈 13% for barley, and 70 to 115% with RSD 〈 18% for wheat. The complexity of these matrices requires the calibration in matrix and the diluted standard addition calibration (DSAC) procedure has been shown to be an excellent option to compensate for the matrix effect and the losses of the analytes in the extraction. Real samples of barley and wheat were analyzed and 60% presented concentrations of paraquat above the maximum limits allowed by the European Union. The modified QuPPe method combined with DSAC and HILIC-UHPLC-MS/MS demonstrated to be an effective approach to determine QUATs in barley and wheat, and is a good alternative for routine analysis. The use of the biosorbent chitosan is effective, low cost and more ecological when compared to others conventional sorbents.〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1588〈/p〉 〈p〉Author(s): Nicole Klaassen, Victor Spicer, Oleg V. Krokhin〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Peptide retention standards are widely used by chromatography specialists. They can be used for quality control of peptide separations (separation efficiency, selectivity, retention values) and for accurate concatenation of retention data from multiple acquisitions in proteomics. So far the repertoire of available retention standards is mostly limited to reversed-phase separations. We introduce a synthetic peptide mixture which can be used in conjunction with the most popular peptide separation techniques: reversed-phase (RPLC), strong-cation exchange (SCX), (strong-anion exchange) SAX and hydrophilic interaction liquid chromatography (HILIC). Target sequences were first designed 〈em〉in-silico〈/em〉 using Sequence-Specific Retention Calculator models covering all major peptide separation mechanisms. Peptides were also designed while keeping in mind the simplicity of retention time assignment using MS detection: they all have nearly identical masses and identical intense 〈em〉y〈sub〉3〈/sub〉〈/em〉 fragment ions. This contribution demonstrates the application of this mixture for characterization of eight HILIC as well as SAX, SCX and C18 columns.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 26 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Anthony R. Horner, Rachael E. Wilson, Stephen R. Groskreutz, Bridget E. Murray, Stephen G. Weber〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Predicting retention and enthalpy allows for the simulation and optimization of advanced chromatographic techniques including gradient separations, temperature-assisted solute focusing, multidimensional liquid chromatography, and solvent focusing. In this paper we explore the fits of three expressions for retention as a function of mobile phase composition and temperature to retention data of 101 small molecules in reversed phase liquid chromatography. The three retention equations investigated are those by Neue and Kuss (NK) and two different equations by Pappa-Louisi et al., one based on a partition model (PL-P) and one based on an adsorption model (PL-A). More than 25 000 retention factors were determined for 101 small molecules under various mobile phase and temperature conditions. The pure experimental uncertainty is very small, approximately 0.22% uncertainty in retention factors measured on the same day (2.1% when performed on different days). Each of the three equations for ln(〈em〉k)〈/em〉 was fit to the experimental data based on a least-squares approach and the results were analyzed using lack-of-fit residuals. The PL-A model, while complex, gives the best overall fits. In addition to examining the equations’ adequacy for retention, we also examined their use for apparent retention enthalpy. This enthalpy can be predicted by taking the derivative of these expressions with respect to the inverse of absolute temperature. The numerical values of the fitted parameters based on retention data can then be used to predict retention enthalpy. These enthalpy predictions were compared to those obtained from a modified van ‘t Hoff equation that included a quadratic term in inverse temperature. Based on analysis of 1 211 van ‘t Hoff plots (solute-mobile phase-day combinations), ninety-eight percent showed a significantly better fit when using the modified van ‘t Hoff expression, justifying its use to provide apparent enthalpies as a function of mobile phase composition and temperature. The foregoing apparent enthalpies were compared to the apparent enthalpies predicted by the three models. The PL-A model, which contains a temperature dependent enthalpy, provided the best enthalpy prediction. However, there is virtually no correlation between the overall lack of fit to experimental ln(〈em〉k)〈/em〉 for each model and the corresponding lack of fit of the linear (in 1/T) van ‘t Hoff expression. Thus, the temperature-dependent enthalpy is apparently not the cause of a model’s ability to fit ln(〈em〉k)〈/em〉 as a function of mobile phase composition and temperature. The value in these expressions is their ability to predict chromatograms, allowing for optimization of an advanced chromatographic technique. The two simpler models NK and PL-P, which do not contain a temperature dependent enthalpy, have their merits in modelling retention (NK being the better of the two) and enthalpy (PL-P being the better of the two) if a simpler expression is required for a given application.〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1588〈/p〉 〈p〉Author(s): Irina Timofeeva, Daria Kanashina, Kira Stepanova, Andrey Bulatov〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A simple and highly-available air-assisted dispersive liquid-liquid microextraction procedure with organic phase solidification (AA-DLLME-OPS) was developed as new approach for pretreatment of complex sample matrix. Menthol was investigated as novel extractant for the AA-DLLME-OPS. In this procedure, a cloudy solution of fine molten menthol droplets is formed when a mixture of molten menthol and aqueous sample is rapidly aspirated into a dispenser and injected into an extraction vial. In the AA-DLLME-OPS, air bubbles promote molten menthol dispersion into aqueous sample phase. Finally, the obtained mixture is cooled and menthol phase is solidified because of the low melting point, which facilitates collection for analysis. To demonstrate the efficiency of the suggested approach, the AA-DLLME-OPS procedure was applied for the HPLC-UV determination of benzoic and sorbic acids as proof-of-concept analytes in beverages and soy sauce samples. The procedure developed provides microextraction of benzoic and sorbic acids from samples with recovery from 93 to 105% and from 96 to 101%, respectively. Under optimal experimental conditions the linear detection ranges were found to be 0.1–150 mg L〈sup〉−1〈/sup〉 for benzoic acid and 0.05–100 mg L〈sup〉−1〈/sup〉 for sorbic acid with LODs calculated from a blank test, based on 3σ, 0.03 mg L〈sup〉−1〈/sup〉 and 0.02 mg L〈sup〉−1〈/sup〉, respectively.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0021967318315504-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 28 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Kaige Zhang, Chuang Liu, Shuangying Li, Jing Fan〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Hydrophobic deep eutectic solvents (DESs) are a new class of green solvents, and their research and application are a brand new area. So far, only a few hydrophobic DESs have been reported as extraction solvents. In this paper, five kinds of hydrophobic DESs composed of trioctylmethylammonium chloride and hydroquinone, 4-phenylphenol or 4-cyanophenol are designed and prepared for the first time. Melting point / glass transition temperature and density are also determined for these DESs. Coupled with HPLC, these hydrophobic DESs have been used as extractants in vortex-assisted liquid-liquid microextraction for the selective enrichment and indirect determination of formaldehyde. The optimization of reaction and extraction conditions, such as pH value, reaction time and temperature, concentration of 2,4-dinitrophenylhydrazine, type and dosage of the extraction solvent, speed and time of vortex, salt addition and centrifugation time are investigated in detail. It is found that under the optimized experimental conditions, the calibration curve of this method is linear in the range of 1.0–200.0 μg L〈sup〉−1〈/sup〉 with the linear correlation coefficient (r〈sup〉2〈/sup〉) of 0.9994. The limit of detection (S/N = 3) and limit of quantification (S/N = 10) are 0.2 μg L〈sup〉−1〈/sup〉 and 1.0 μg L〈sup〉−1〈/sup〉, and the intra-day and inter-day precision (RSD, n = 5) are 1.1% and 3.5%, respectively. The interference of some common coexisting ions and neutral molecules have been also tested. The proposed method has been successfully used for the determination of formaldehyde from biological and indoor air samples. The recovery of formaldehyde is in the range from 83.1% to 104.4%, and the relative standard deviation is lower than 5.9%. Furthermore, the analytical parameters of the proposed method have been compared with other extraction and microextraction methods.〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1588〈/p〉 〈p〉Author(s): Miaotian Sun, Sheila Ruiz Barbero, Monika Johannsen, Irina Smirnova, Pavel Gurikov〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this work, inverse supercritical fluid chromatography was applied to characterize the surface of four silica materials (three commercial Kromasils and one silica aerogel) from chromatographic retention data. Retention factors at various pressures (150–300 bar), temperatures (25–60 °C) and modifier concentrations (5–20 vol.% methanol in CO〈sub〉2〈/sub〉) for a set of representative 17 solutes were correlated with the solute properties by the linear solvation energy relationships (LSER). Two types of the LSER models were identified based on different criteria. Firstly, a generally valid model with two descriptors concerning dipolarity/polarizability and solute hydrogen-bonding acceptor ability was constructed. Secondly, a group of specific models for each particular silica material was proposed. According to the statistical analysis of the modeling results, the acid-basic interactions were demonstrated to have a major contribution to the retention for all studied silicas. The intensity of these interactions decreases with increasing methanol concentration in the mobile phase, possibly due to the mixed mechanism of competitive adsorption of the modifier on silanol groups and modification of mobile phase property. Moreover, retention factors measured under constant conditions (p, T, methanol concentration) for a pair of the materials were found to be proportional in logarithmic scale implying the transferability of the adsorption free energies and the adsorption constants across four studied silica materials.〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1588〈/p〉 〈p〉Author(s): Huikai Shao, Haibo Zhou, Tingting Zhang, Xianglong Zhao, Zhengjin Jiang, Qiqin Wang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A novel molecularly imprinted inorganic-organic hybrid monolith (MIP hybrid monolith) was fabricated through a facile single-step polymerization strategy with levofloxacin (LEV) as the template, 3-aminopropyltriethoxysilane-methacrylic acid as the hybrid functional monomer and ethylene glycol dimethacrylate as the crosslinker in a mixed porogen of methanol, toluene and dodecanol. The optimized LEV-MIP hybrid monolith was characterized using scanning electron microscopy and fourier transform-infrared spectroscopy. Uniform monolithic matrix with large through-pores in the network skeleton of LEV-MIP hybrid monolith was observed. The influence of polymerization conditions on the specific recognition behavior of the resulting monolith was systematically investigated. The LEV-MIP hybrid monolith exhibited much better adsorption (3.62 times) and selectivity towards LEV in comparison with non-imprinted hybrid monolith. Furthermore, the LEV-MIP hybrid monolith based solid-phase extraction combining with liquid chromatography-mass spectrometry was applied for the selective determination of fluoroquinolones (FQs) in infant formula powder. The average recoveries of six FQs in milk powders spiked at 20, 50 and 100 μg kg〈sup〉−1〈/sup〉 were in the range of 82.91–102.00% with the precision of 1.04–7.39%. The limit of detection and limit of quantitation of the proposed method were in a range of 0.19–1.24 μg kg〈sup〉−1〈/sup〉 and 0.63–4.13 μg kg〈sup〉−1〈/sup〉, respectively.〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1588〈/p〉 〈p〉Author(s): María J. Trujillo-Rodríguez, Jared L. Anderson〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A new class of magnetic ionic liquid (MIL) containing paramagnetic cations has been applied for 〈em〉in situ〈/em〉 dispersive liquid-liquid microextraction in the determination of both polar and non-polar pollutants, including ultraviolet filters, polycyclic aromatic hydrocarbons, alkylphenols, a plasticizer and a preservative in aqueous samples. The MILs were based on cations containing Ni(II) metal centers coordinated with four N-alkylimidazole ligands and chloride anions. The MILs were capable of undergoing 〈em〉in situ〈/em〉 metathesis reaction with the bis[(trifluoromethyl)sulfonyl]imide ([NTf〈sub〉2〈/sub〉〈sup〉−〈/sup〉]) anion during the microextraction procedure, generating a water-immiscible extraction solvent containing the preconcentrated analytes. The MIL was then isolated by magnetic separation, followed by direct analysis using reversed-phase high performance liquid chromatography with diode array detection. Among all of the studied MILs, those containing the N-butylimidazole and N-benzylimidazole ligands ([Ni(C〈sub〉4〈/sub〉IM)〈sub〉4〈/sub〉〈sup〉2+〈/sup〉]2[Cl〈sup〉-〈/sup〉] and [Ni(BeIM)〈sub〉4〈/sub〉〈sup〉2+〈/sup〉]2[Cl〈sup〉-〈/sup〉], respectively) exhibited the best extraction performance. The method under optimum conditions required 5 mL of sample at pH 3, 20 mg of [Ni(C〈sub〉4〈/sub〉IM)〈sub〉4〈/sub〉〈sup〉2+〈/sup〉]2[Cl〈sup〉-〈/sup〉] or 30 mg of [Ni(BeIM)〈sub〉4〈/sub〉〈sup〉2+〈/sup〉]2[Cl〈sup〉-〈/sup〉], 300 μL of acetone or acetonitrile as dispersive solvent (depending on the MIL), a 1:2 M ratio of MIL to [NTf〈sub〉2〈/sub〉〈sup〉−〈/sup〉], and 3 min of vortex. The developed method achieved higher extraction efficiency compared to the conventional MIL-dispersive liquid-liquid microextraction mode, with extraction efficiencies of 46.8–88.6% and 65.4–97.0% for the [Ni(C〈sub〉4〈/sub〉IM)〈sub〉4〈/sub〉〈sup〉2+〈/sup〉]2[Cl〈sup〉-〈/sup〉] and the [Ni(BeIM)〈sub〉4〈/sub〉〈sup〉2+〈/sup〉]2[Cl〈sup〉-〈/sup〉] MILs (at a spiked level of 81 μg L〈sup〉-1〈/sup〉), respectively, limits of detection down to 5.2 μg L〈sup〉-1〈/sup〉, and inter-day relative standard deviation lower than 16%.〈/p〉〈/div〉

Description: 〈p〉Publication date: 22 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1587〈/p〉 〈p〉Author(s): F. Bezold, M. Minceva〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Centrifugal partition chromatography (CPC) is a well-established technology for natural compound separation. However, the separation of hydrophobic compounds is still challenging since the number of non-aqueous biphasic systems that can be used in CPC is limited. In this work, we evaluate quaternary solvent systems composed of 〈em〉n〈/em〉-heptane, methanol, and a eutectic solvent composed of L-menthol and levulinic acid, containing DES-constituents in both phases. It was evaluated whether the phases of the systems can be used as stationary and mobile phases for CPC separations. For this purpose, solutes that cover a broad range of octanol-water partition coefficients, i.e. hydrophobic to hydrophilic compounds, were used and shake flask experiments were performed to determine solute partition coefficients. The partition coefficients indicated that the more hydrophobic compounds were in the favored range for CPC and, thus, the systems are high potential candidates for the separation of hydrophobic compounds. In this particular solute set, the biphasic systems were most suitable for compounds with octanol-water partition coefficients between 2.1 and 12.0. It was shown that the biphasic systems with low initial DES-content are stable in presence of water, while L-menthol precipitates from the biphasic systems with high initial DES content when water is added. High stationary phase retention of up to 79.1% could be obtained and the selected model compounds were separated with high resolution in pulse injections, which confirmed the high potential of the biphasic solvent systems for CPC.〈/p〉〈/div〉

Description: 〈p〉Publication date: 22 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1587〈/p〉 〈p〉Author(s): Saman Monjezi, Mason Schneier, Jaeyeong Choi, Seungho Lee, Joontaek Park〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A theoretical model is proposed to analyze the shape effect on the retention behaviors of rod-like particles in field-flow fractionation. This model is improved from a previous model for slender-body rods by Park and Mittal [Chromatography (2015) 2: 472–487]: The model can predict the retention behaviors of the rods, of which shape is assumed as a prolate ellipsoid, with low and high aspect ratios in various flow conditions of the flow-field flow fractionation. The effects of rod aspect ratio on the retention behaviors of the rods with the same volume are investigated in each operation mode. In normal mode, the retention ratio decreases with increasing aspect ratio. In steric-entropic mode, where we substantially improved the model to evaluate the rod orientation and the cross-sectional concentration distribution more rigorously based on our recent studies [Nanomaterials (2018) 8:130; Chem. Eng. Sci. (2018) 189:396-400], the retention ratio increases with the increasing aspect ratio. In steric mode, the retention ratio decreases with increasing aspect ratio again. Those results are discussed based on how the cross-sectional concentration distributions are affected by the aspect ratio. The new criteria for the prediction of each mode are also discussed and suggested Comparison with the experimental data shows the qualitative agreement.〈/p〉〈/div〉

Description: 〈p〉Publication date: 22 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1587〈/p〉 〈p〉Author(s): Xiaojie Zhao, Kaifeng Tan, Jun Xing〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Ionic liquid bonded polysiloxanes (PILs) are a class of polysiloxanes whose side chains contain ionic liquid (IL) moieties. Considering their excellent selectivity and thermo-stability, PILs have great potentials in the development of polar stationary phases for gas chromatography. In this paper, a novel synthesis strategy for PILs is proposed to diversify PIL stationary phases and also facilitate the study on relationships between stationary phase structure and separation performances. The polysiloxane with imidazole groups at the side chains was synthesized firstly, and then these imidazole groups further reacted with halogenated compounds to produce various IL groups. Upon this, fifteen PIL stationary phases differing in IL content, IL group or combination of different IL groups have been synthesized and used to prepare capillary columns through static coating method. These columns have quite different general polarity indexes (the average value of all Rohrschneider-McReynolds constants in this paper) falling in a broad range from 218 to 717, and most columns have column efficiency values over 3000 plates/m. In addition, IL content, structure of the IL and combination of different IL groups have noticeable influences on interaction features of the stationary phases. After that, the separation performances of these PIL stationary phases were demonstrated by separating various mixed samples of aliphatic esters, dichloro-anilines, alcohols, aromatic amines, substituted alkanes, and so on. In order to reveal the relationship of interaction characteristics and separation performances, a set of indexes of contribution rates (CRs) is proposed. Based on CRs, the separation selectivity of the PIL stationary phases has been discussed in detail. The results indicate that there are significant differences in the separation selectivity not only between PILs and conventional polar stationary phases, but also among different PILs. All of these imply a family of practical PILs with special selectivity could be constructed upon this synthesis strategy.〈/p〉〈/div〉

Description: 〈p〉Publication date: 22 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1587〈/p〉 〈p〉Author(s): Malgorzata Gbylik-Sikorska, Anna Gajda, Ewelina Nowacka-Kozak, Andrzej Posyniak〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A multi-residue method was developed for the determination of 45 antibacterial compounds in mushrooms - 〈em〉Agaricus bisporus.〈/em〉 The method is based on liquid-liquid extraction with acetonitrile with addition of trichloroacetic acid and filtration through sodium sulphate, followed by the identification and quantification of the analyte residues by ultra-high performance liquid chromatography triple quadrupole tandem mass spectrometry (UHPLC–MS/MS). Satisfactory linearity was obtained for all compounds with regression coefficients greater than 0.99. The mean recoveries of antibacterial agents were in the range of 73% - 118%. Repeatability and intra-lab reproducibility were lower than 10% and 15%, respectively. The limit of detection ranged from 0.3–3.0 μg kg〈sup〉−1〈/sup〉 and the limit of quantification was in the range of 1.0 - 10. 0 μg kg〈sup〉−1〈/sup〉 depending on analyte. The proposed method can be successfully applied for the determination of antibiotics in commercially available mushrooms.〈/p〉〈/div〉

Description: 〈p〉Publication date: 8 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1586〈/p〉 〈p〉Author(s): Valentina D’Atri, Reinhard Pell, Adrian Clarke, Davy Guillarme, Szabolcs Fekete〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Antibody drug conjugates (ADCs) belong to the fastest growing class of therapeutic agents for cancer therapy. In preclinical and clinical studies, there is a significant number of site-specific ADCs (also known as third generation ADCs), which are more homogeneous than their previous generations. These new ADC formats, in which the inter-chain disulphide bridges (hinge cysteines) are not reduced, also need to be deeply characterized. In particular, various quality attributes (QAs) have to be determined, such as free antibody level, average drug to antibody ratio (DAR) and drug distribution. In this contribution, a non-commercial site-specific conjugated ADC has been analyzed by RPLC. Our results demonstrated that RPLC has a huge potential to determine QAs and can replace the historically used HIC methods as RPLC provides better separation quality for such type of ADCs. Site-specific ADCs can be analyzed in RPLC at intact level without the need for sample preparation. A further advantage of RPLC is that it enables the direct coupling to MS and thus allows the fine identification of all eluting species.〈/p〉〈/div〉

Description: 〈p〉Publication date: 22 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1587〈/p〉 〈p〉Author(s): Yiran Wang, Giorgio Carta〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The internal structure of ceramic hydroxyapatite CHT Type I and Type II and the adsorption behavior of a monoclonal antibody in monomeric and dimeric forms are determined. Both CHT types contain elongated nanocrystals with size about 20 x 100 nm for Type I and about 50 x 200 nm for Type II. Internal porosities and apparent pore radii based on inverse size exclusion chromatography are 0.73 and 30 nm for Type I and 0.70 and 49 nm for Type II. Adsorption isotherms show maximum capacities of 95 and 110 mg/mL of particle for monomer and dimer on Type I and of 55 and 67 mg/mL of particle on Type II, in approximate agreement with the ratio of surface areas. The isotherms are dependent on the Na〈sup〉+〈/sup〉 concentration consistent with an electrostatically driven mechanism. Mixture adsorption shows selectivity toward the dimer, with mean α-values of 4.3 and 5.8 for Type I and II, respectively. Effective pore diffusivities for non-binding conditions are 0.54 × 10〈sup〉−7〈/sup〉 and 0.33 × 10〈sup〉−7〈/sup〉 cm〈sup〉2〈/sup〉/s for monomer and dimer in CHT Type I increasing to 0.94 × 10〈sup〉−7〈/sup〉 and 0.66 × 10〈sup〉−7〈/sup〉 cm〈sup〉2〈/sup〉/s as a result of the larger pore size of Type II. Effective pore diffusivities for strong binding conditions, obtained by confocal microscopy, are much smaller than the non-binding values for Type I but essentially the same for Type II, indicating that diffusional hindrance by the bound protein is greater in the smaller pores of Type I. Mixture confocal adsorption experiments show that the competitive binding kinetics is largely controlled by pore diffusion in both CHT types with the dimer readily displacing the monomer even for strong binging conditions, but is much faster on Type II.〈/p〉〈/div〉

Description: 〈p〉Publication date: 22 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1587〈/p〉 〈p〉Author(s): Bin Hu, Haoyuan Wang, Linfeng He, Yi Li, Cheng Li, Zhiqing Zhang, Yuntao Liu, Kang Zhou, Qing Zhang, Aiping Liu, Shuxiang Liu, Yadong Zhu, Qingying Luo〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In order to increase the utilization of cherry seeds, ultrasonic-microwave assisted aqueous enzymatic extraction (UMAAEE) was used to extract cherry seed oil. Parameters of UMAAEE were optimized by Plackett-Burman design followed by Box-Behnken design. The oil recovery of 83.85 ± 0.78% was obtained under optimum extraction conditions of a 2.7% concentration of enzyme cocktail comprising cellulase, hemicellulase and pectinase (1/1/1, w/w/w), ultrasonic power of 560 W, microwave power of 323 W, extraction time of 38 min, extraction temperature of 40 °C, enzymolysis temperature of 40 °C, pH of 3.5, liquid to solid ratio of 12 mL/g, enzymolysis time of 240 min and particle size less than 0.425 mm. There were no significant differences in the fatty acid compositions of cheery seed oil by UMAAEE and Soxhlet extraction, and oil by UMAAEE possessed superior physicochemical properties and higher content of bioactive constituents. Scanning electron microscopy illustrated that enzyme hydrolysis and ultrasonic-microwave treatment causing the structural degradation of cherry seed was the main driving force for extraction. In this study, all results suggest that UMAAEE is an effective method to extract cherry seed oil.〈/p〉〈/div〉

Description: 〈p〉Publication date: 8 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1586〈/p〉 〈p〉Author(s): John Mommers, Sjoerd van der Wal〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Orthogonality can be used as a selection parameter for two-dimensional chromatography column selection (e.g. in GC × GC or LC × LC) or for method optimization purposes, both aiming for maximal orthogonality for a particular analytical application. In order to improve the concurrence of two-dimensional chromatography expert’s orthogonality grading, two orthogonality metrics, %FIT and %BIN, were developed, evaluated and compared with the Asterisks orthogonality metric. The %BIN is a bin counting approach where the number of bins is fixed at 25 and deviations from the expected average number of peaks per bin is used as the basis for the orthogonality calculation. The %FIT is based on fitting polynomials of degree two, through the xy and the yx data and calculating the average minimal distance and standard deviation of all data points above and below the fitted polynomials. The orthogonality metrics were evaluated by using 14 different types of computer generated xy datasets and two measured LC × LC datasets. Both %FIT and %BIN, were shown to have a larger discriminative power than the Asterisks equations, and are in good agreement with the orthogonality scores for 2D-chromatograms provided by nine experts.〈/p〉〈/div〉

Description: 〈p〉Publication date: 8 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1586〈/p〉 〈p〉Author(s): Shi Qiu, Bharathi Avula, Shaohua Guan, Ranga Rao Ravu, Mei Wang, Jianping Zhao, Ikhlas A. Khan, Maud Hinchee, Xing-Cong Li〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉〈em〉Paenibacillus〈/em〉 sp. MS2379 is a highly efficient microbial strain producing fusaricidins, a class of lipopeptides that have demonstrated strong antifungal activities against a broad array of fungal pathogens. An integrated approach combining chromatographic fractionation, UHPLC-QTOF-MS analysis, and NMR spectroscopic interpretation was employed to characterize antifungal metabolites produced by this microbial strain, resulting in the identification of 48 fusaricidins including 30 cyclic and 18 open-chain species. In this regard, UHPLC-QTOF-MS played a vital role in determining structures of 28 new fusaricidins through peptide fragment analysis. The structural determination of the new fusaricidins by the high-resolution mass spectrometry was validated by follow-up isolation and NMR spectroscopic analysis of representative compounds. It is worth noting that novel fusaricidins with amino acid residues of serine and γ-aminobutyric acid were identified, which is of great biosynthetic significance for this biologically important class of compounds. The present study again illustrates the power of UHPLC-QTOF-MS for structural identification of lipopeptides, and the structural diversity of the identified fusaricidins makes this microbial strain unique as a potential biocontrol agent.〈/p〉〈/div〉

Description: 〈p〉Publication date: 8 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1586〈/p〉 〈p〉Author(s): Drew C. Hayman, R. Andrew Shalliker〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉The performance of a particle packed column will inevitably degrade through use or misadventure. ‘Active flow technology’ (AFT) is known to greatly improve the performance of pristine columns, but is as of yet untested when used on columns that have degraded significantly. In this study AFT was used to regenerate a degraded column, where the reduced plate height and asymmetry values were 3.5 and 1.25 respectively. Once the AFT fittings were fitted to the column outlet and the flow segmentation ratio adjusted to 28% from the radial central exit port, the reduced plate height decreased to 2.0, and the bands were almost perfectly symmetrical with asymmetry factors equal to 1.04. Subsequently, the performance of the degraded column with AFT fittings provided performance that was comparable to that of a new conventional column fitted with traditional end fittings.〈/p〉 〈p〉The separation power of the degraded conventional column and that of the same column fitted with the AFT end fittings was then tested using the separation of oligostyrenes. In AFT mode, detection was undertaken at both the radial central exit port of the column and the peripheral exit port. The resulting separation that was achieved from the radial central exit port was superior to that observed on the conventional column, whereas, the separation observed from the peripheral port was very poor. It was subsequently determined that the reason for the degraded performance of the conventional column was a result of increased heterogeneity associated with the packing material in the wall region of the column.〈/p〉 〈/div〉

Description: 〈p〉Publication date: 8 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1586〈/p〉 〈p〉Author(s): Yan He, Paul Brown, Michele R. Bailey Piatchek, James A. Carroll, Michael T. Jones〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Polysorbates are complex mixtures of over a thousand components with a wide range of hydrophobicity. This paper describes a methodology for characterization of heterogeneity and stability of polysorbates in therapeutic protein formulation. The method utilizes on-line coupling of a hydrophobic interaction chromatography (HIC) column with reverse phase liquid chromatography (RPLC) and charged aerosol detection (CAD)/mass spectrometer (MS). The addition of a low concentration of formic acid and organic solvent (e.g. 0.05% formic acid and 3% acetonitrile) in the mobile phase enables the use of the HIC column to separate small molecule excipients (including major components of polysorbates) and the large protein molecules by a mixed mechanism of size exclusion chromatography (SEC) and RPLC. The protein and the charged excipients, which elute early from the HIC column, are directed by a switching valve to waste. The polysorbates and other neutral excipients, which elute later from the HIC column, are directed to the RPLC column for further separation. The separated polysorbate components are detected by CAD, and characterized by MS. This method has been used to characterize the degradation of polysorbate 80 (PS80) in placebo and protein formulations. Our studies have revealed different degradation behavior of PS80 in placebo vs. protein formulation.〈/p〉〈/div〉

Description: 〈p〉Publication date: 8 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1586〈/p〉 〈p〉Author(s): Sul Lee, Su-Jin Kim, Eunjung Bang, Yun-Cheol Na〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉An enantiomeric separation method for underivatized free amino acids (AAs) using a partial filling technique with CE-MS was developed for the determination of D-AAs in vinegars. A typical chiral separation method was performed with different concentrations of (18-crown-6)-2,3,11,12-tetracarboxylic acid (18C6H4) dissolved in water or formic acid as the background electrolyte. Seventeen AAs, excluding proline and asparagine, were separated, showing chiral resolution values (Rs) ranging from 0.5 to 21.0. These results included baseline separations of 11 AAs, the peaks of which were observed as the ions [AA+18C6H4+H]〈sup〉+〈/sup〉. The migration order of the chiral AAs was also evaluated, and the L-AAs migrated faster than the counterpart D-AAs except for serine, threonine and methionine when using (+)-18C6H4. To reduce contamination of the ESI source by the nonvolatile chiral selector and improve the ionization efficiency in partial filling technique, the separation zone length was adjusted to 70% of the capillary, which was filled with 30 mM 18C6H4 in water. This method showed a similar separation efficiency as the typical method, and the separated AA peaks were observed as free AA ions, [AA+H]〈sup〉+〈/sup〉. The optimized method provided limits of detection (LODs) ranging from 0.07 to 1.03 μg/mL and good linearity (R〈sup〉2〈/sup〉 〉 0.99) up to 50 μg/mL for DL-AAs. The developed method was utilized to determine DL-AAs in vinegars with a simple pretreatment process. It may be extended to sensitive AA analysis in the determination of minor enantiomeric impurities in the major component.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 27 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Ning An, Pisheng Gong, Henglei Hou, Weiya Chi, Haibo Jin, Lan Zhao, Qiqi Tan, Xu Tang, Fei Wang, Hongchao Jin, Rongyue Zhang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The macroporous microspheres with core-shell structure, based on a copolymer of 4-Vinylbenzyl chloride, glycidyl methacrylate, and ethylene glycol dimethacrylate, were fabricated through atom transfer radical polymerization suspension polymerization. The microspheres showed 100-200 nm pores in shell and 500-900 nm pores in core. The shell was hydrophilic modified through grafting of poly(N-hydroxyethyl acrylamide) onto the shell surface for reducing adsorption of proteins. The core was coupled with a ligand of poly(ethylene imine) that could bind the proteins. Feedstock of avian influenza virus could be purified on these modified microspheres through negative chromatography. Avian influenza virus cannot enter the core and was recovered from the flow-through, while other proteins with negative charges were able to penetrate into the core and bind to the poly(ethylene imine) ligands. The dynamic binding capacity of proteins was higher on this medium (61 mg/mL) than the commercially available resin (12 mg/mL, Capto Core 700).〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 27 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Lihong Zhang, Shihua Wu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Countercurrent chromatography (or counter-current chromatography, CCC) is a unique support-free liquid-liquid partition chromatography. Since it was invented by Y. Ito in 1960s, CCC has been widely accepted and applied as popular separation and purification technique for natural and synthetic complex. However, up to date there is little study to address on hydrophobic and hydrophilic interactions in CCC process, although hydrophobic interaction chromatography (HIC) and hydrophilic interaction chromatography (or hydrophilic interaction liquid chromatography, HILIC) as solid-support chromatographic techniques are widely applied at different stages of downstream processing. In fact, hydrophobic and hydrophilic interactions might be more popular in CCC separation than that in the liquid chromatography. For example, adding small solvents or additives in two-phase solvent systems may change significantly hydrophobic or hydrophilic interactions between solvents and solutes. Normally, CCC separation employs a light and hydrophobic organic phase as the stationary phase, and a heavy and hydrophilic aqueous phase as the mobile phase. Hydrophobic interactions between the solvent system and solutes (targets) will increase the partition coefficients (〈em〉K〈/em〉 values) of solutes and lengthen retention time, while hydrophilic interactions will reduce the 〈em〉K〈/em〉 values and separation time. In this work, we aim to provide a general insight on the hydrophobic and hydrophilic interactions in CCC separation. We also highlight the current advances in utilizing the hydrophobic and hydrophilic interactions for 〈em〉K〈/em〉-targeted CCC separation and purification.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 27 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Attila Bajtai, István Ilisz, Dian H.O. Howan, Gábor K. Tóth, Gerhard K.E. Scriba, Wolfgang Lindner, Antal Péter〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Sixteen pairs of enantiomeric dipeptides were separated on four chiral ion-exchanger-type stationary phases based on 〈em〉Cinchona〈/em〉 alkaloids. Anion-exchangers (QN-AX, QD-AX) and zwitterionic phases [ZWIX(+)™ and ZWIX(-)™] were studied in a comparative manner. The effects of the nature and concentrations of the mobile phase solvent components and organic salt additives on analyte retention and enantioseparation were systematically studied in order to get a deeper insight into the enantiorecognition mechanism. Moreover, experiments were performed in the temperature range 10–50°C to calculate thermodynamic parameters like changes in standard enthalpy, Δ(ΔH°), entropy, Δ(ΔS°), and free energy, Δ(ΔG°) on the basis of van't Hoff plots derived from the ln α vs. 1/T curves. Elution sequences of the dipeptides were determined in all cases and, with a few exceptions, they were found to be opposite on the pseudoenantiomeric stationary phases as of QN-AX/QD-AX and of ZWIX(+) and ZWIX(-). The stereoselective retention mechanism is based on electrostatically driven intermolecular interactions supported by additional interaction increments mainly determined by the absolute configuration of the chiral C8 and C9 atoms of the quinine and quinidine moieties.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 27 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): A. Vallejos-Almirall, C. Folch-Cano, A. Rosas, C. Vergara〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Ultraviolet radiation from sunlight causes DNA damage in skin cells by formation of photoproducts, mainly cyclobutane pyrimidine dimers (CPD), which are reverted by exogenous CPD-photolyase, preventing photoaging and skin cancer. High performance liquid chromatography tandem mass spectrometry method for quantification of CPD-photolyase activity was developed to search new enzymes sources for dermatology or clinical studies. The method was based in the enzymatic conversion of a 15mer oligonucleotide, containing a center cyclobutane thymidine dimer, to the restored 15mer oligonucleotide. Three ion pair reagent were evaluated by response surface methodology to increase mass intensities. Additionally, chromatographic separation of oligonucleotides was performed. The selected mobile phase was 15 mM diisopropylethylamine / 20 mM hexafluoroisopropanol in methanol. The method allowed total separation between the oligonucleotides studied (resolution of 2.3) by using the core shell technology, which reduce the diffusion time of the analyte into the column, increasing the efficiency and minimizing the analysis time at 7 min. The mass spectrometry detection allowed a high selectivity and sensitivity. This is the first time where MRM modality has been employed with this specific purpose. Oligonucleotides recovery from reaction mixture was ∼ 94 % and the limit of quantification was 13.4 nM for 15mer. The method was evaluated with a recombinant CPD-photolyase from 〈em〉Synechococcus leopoliensis〈/em〉 using purified and crude protein extract. CPD-photolyase could be measured in terms of activity for enzymatic kinetics studies, for evaluation of UV-R effects in (micro)organisms and to identify new enzymes.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 26 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Rok Ambrožič, Petra Modic, Gorazd Hribar, Aleš Podgornik〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A chromatographic system was adapted to allow monitoring of eluent of preparative column via absorbance and with the chromatographic analysis of the target macromolecule on the same chromatographic system. The proposed approach was tested on important macromolecules, such as monoclonal antibodies, monoclonal antibody aggregates and plasmid DNA (pDNA). A frontal analysis was made on the preparative column, while a chromatographic on-line analysis was performed by sequentially injecting the preparative column outlet on a convection-based analytical column, operating on the same chromatographic system. Cation and/or anion exchangers were used as the chromatographic media (along with a protein A), depending on the sample to be purified. The method was found to be robust and reproducible. To adjust the limit of detection, an algorithm varying the number of injections was used, enabling accurate monitoring of an early breakthrough for concentrations below 1% of the feed concentration. The accuracy varies according to the applied flow rate, but it is typically in the range of few percent, or even below. Due to its simplicity and flexibility, the proposed method can be easily adapted to a pharmaceutical environment.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 26 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Matthew J. Sorensen, Kelsey E. Miller, James W. Jorgenson, Robert T. Kennedy〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Improvements in sample preparation, separation, and mass spectrometry continue to expand the coverage in LC-MS based lipidomics. While longer columns packed with smaller particles in theory give higher separation performance compared to shorter columns, the implementation of this technology above commercial limits has been sparse due to difficulties in packing long columns and successfully operating instruments at ultrahigh pressures. In this work, a liquid chromatograph that operates up to 35 kpsi was investigated for the separation and identification of lipid species from human plasma. Capillary columns between 15-50 cm long were packed with 1.7 µm BEH C18 particles and evaluated for their ability to separate lipid isomers and complex lipid extracts from human plasma. Putative lipid class identifications were assigned using accurate mass and relative retention time data of the eluting peaks. Our findings indicate that longer columns packed and operated at 35 kpsi outperform shorter columns packed and run at lower pressures in terms of peak capacity and numbers of features identified. Packing columns with relatively high concentration slurries (200 mg/mL) while sonicating the column resulted in 6 to 34 % increase in peak capacity for 50 cm columns compared to lower slurry concentrations and no sonication. For a given analysis time, 50 cm long columns operated at 35 kpsi provided a 20-95% increase in chromatographic peak capacity compared with 15 cm columns operated at 15 kpsi. Analysis times up to 4 h were evaluated, generating peak capacities up to 410 ± 5 (n = 3, measured at 4σ) and identifying 480 ± 85 lipids (n = 2). Importantly, the results also show a correlation between the peak capacity and the number of lipids identified from a human plasma extract. This correlation indicates that ionization suppression is a limiting factor in obtaining sufficient signal for identification by mass spectrometry. The result also shows that the higher resolution obtained by shallow gradients overcomes possible signal reduction due to broader, more dilute peaks in long gradients for improving detection of lipids in LC-MS. Lastly, longer columns operated at shallow gradients allowed for the best separation of both regional and geometrical isomers. These results demonstrate a system that enables the advantages of using longer columns packed and run at ultrahigh pressure for improving lipid separations and lipidome coverage.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 27 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Simone Carradori, Daniela Secci, Paolo Guglielmi, Marco Pierini, Roberto Cirilli〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Recently it has been reported that immobilized chlorinated-type chiral stationary phases based on cellulose tris(3,5-dichlorophenylcarbamate) are able to express an outstanding enantioselectivity towards the structure of 2-(benzylsulfinyl)benzamide. We now introduce two homologue series of chiral sulfoxides based on the same 2-(sulfinyl)benzoyl core as the prototype of new selectands for HPLC, whose enantioselectivity could be modulable through the replacement of the benzyl group with an unbranched alkyl chain varying in length from 1 to 5 carbon atoms. HPLC parameters such as mobile phase composition and column temperature have been carefully evaluated in order to get pertinent structure-enantioselectivity relationships. The enantiomer elution order was unambiguously determined by a combined strategy involving theoretical and experimental procedures. Two cases of temperature-dependent inversion of the elution order of enantiomers in the operative temperature range of chiral chromatographic support were observed.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 26 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Amar Oedit, Bastiaan Duivelshof, Peter Lindenburg, Thomas Hankemeier〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉A major strength of capillary electrophoresis (CE) is its ability to inject small sample volumes. However, there is a great mismatch between injection volume (typically 〈100 nL) and sample volumes (typically 20-1500 µL). Electromigration-based sample preparation methods are based on similar principles as capillary electrophoresis. The combination of these methods with capillary electrophoresis could tackle obstacles in the analysis of dilute samples.〈/p〉 〈p〉This study demonstrates coupling of three-phase microelectroextraction (3PEE) to CE for sample preparation and preconcentration of large volume samples while requiring minimal adaptation of CE equipment. In this set-up, electroextraction takes place from an aqueous phase, through an organic filter phase, into an aqueous droplet that is hanging at the capillary inlet. The first visual proof-of-concept for this set-up showed successful extraction using the cationic dye crystal violet. The potential of three-phase microelectroextraction for bioanalysis was demonstrated by successful extraction of the biogenic amines serotonin (5-HT), tyrosine (Tyr) and tryptophan (Trp). Under optimized conditions limit of detection (LOD) was 15 nM and 33 nM for 5-HT and Tyr respectively (with Trp as an internal standard). These LODs are comparable to other, similar preconcentration methods that have been reported in conjunction with capillary electrophoresis. Good linearity (R〈sup〉2〈/sup〉 〉 0.9967) was observed for both model analytes. RSDs for peak areas in technical replicates, interday and intraday variability were all satisfactory, i.e., below 14%. 5-HT, Tyr and Trp spiked to human urine were successfully extracted and separated. These results underline the great potential of three-phase microelectroextraction as an integrated enrichment technique from biological samples and subsequent sensitive metabolomics analysis.〈/p〉 〈/div〉

Description: 〈p〉Publication date: Available online 26 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Lidia Corell, Sergio Armenta, Francesc A. Esteve-Turrillas〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A direct procedure based on thermal desorption-gas chromatography-tandem mass spectrometry (TD-GC-MS-MS) was developed for the fast extraction of seven polychlorinated biphenyls (PCBs) from sediments and soils. PCBs were directly extracted, from 20 to 75 mg of sample, without any chemical pre-treatment or use of organic solvents, after the addition of 10 µL internal standard (PCB 195) in acetone. Sample treatment was totally automated. PCBs were extracted at 250°C for 20 min, using a helium flow and the PCBs were trapped in a cryogenic Tenax trap at -10°C. After that, analytes were directly desorbed at 270°C and introduced to the GC-MS-MS system. Recoveries were established using spiked soil and sediment from 2.5 to 50 ng g〈sup〉−1〈/sup〉, obtaining values from 74 to 127 %. The limits of quantification were from 1.0 to 1.7 ng g〈sup〉−1〈/sup〉 for soil and from 0.3 to 0.4 ng g〈sup〉−1〈/sup〉 for sediments, respectively. Precision, assessed as the relative standard deviation (RSD), was lower than 8 and 11 % for sediment and soil analysis, respectively, except for PCB-28 in soil samples which provided a RSD of 18 %. Certified reference material and field samples were analysed by the proposed TD-GC-MS-MS method. Results were compared by a paired samples Student's t-test with those obtained by a reference extraction procedure based on pressurized solvent extraction, followed by stir bar sorptive extraction, being statistically comparable (α=0.05). A comprehensive greenmetric evaluation of the proposed method was carried out, having the TD extraction a negligible environmental impact as compared to conventional extraction procedures.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 14 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): K. Adamska, A. Voelkel, M. Sandomierski〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Estimation of the properties of mesoporous aluminosilicates in various environments is important when assessing their sorption capacity. Using inverse liquid chromatography (ILC), Hansen solubility parameters (HSP) and linear free energy relationship (LFER) parameters were calculated to determine the properties of aluminosilicates in a protic and an aprotic system, using water and acetonitrile as the mobile phase, respectively. The calculated Hansen parameters, reflecting the ability of the material under investigation to different types of intermolecular interactions, slightly differ depending on the mobile phase used. It was found that in the presence of water the surface of aluminosilicates shows a weaker ability to interact, as evidenced by negative or near-zero 〈em〉e, s, a, b, v〈/em〉 coefficients. Additionally, it was found that the Si/Al ratio in aluminosilicates structure has little effect on the determined parameters.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 14 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Boquan Qu, Lina Zhang, Shaoyan Wang, Yanling Quan, Xiuhong Wu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We herein report the use of an amino-based column and hydrophilic interaction chromatography (HILIC) to separate 14 ginsenosides, namely Rb1, Rb2, Rb3, Rc, Rd, Rf, Re, Rg1, Rg2, Rg3, Rh1, Rh2, F〈sub〉2〈/sub〉, and C-K. In addition to its rapid and efficient ability to separate these ginsenosides, the amino-based column exhibited a good relationship between the ginsenoside capacity factor (〈em〉k〈/em〉′) and molecular weight (〈em〉M〈sub〉w〈/sub〉〈/em〉) and a strict elution order corresponding to the polarity (〈em〉P〈/em〉) of the ginsenosides, as confirmed by thin layer chromatography.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 3 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Léon Reubsaet, Michael J. Sweredoski, Annie Moradian, Brett Lomenick, Roxana Eggleston-Rangel, Spiros D. Garbis〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A proteomic workflow for a simple loss-less manual nano-fractionation (300 nL/fraction) for low µg sample amounts which avoids the need to dry down or transfer fractions to autosampler vials is shown to be feasible. It is demonstrated that the conventional procedure of drying samples down followed by reconstitution negatively affects the number of protein and peptide identifications. Furthermore, these losses seem to disproportionately affect hydrophobic peptides from the drying down and reconstitution step. By collecting and concatenating the fractions while the outlet of the column is submerged in a small predefined volume of 0.2% formic acid, the content of acetonitrile in the collecting vials was lowered such that it was compatible with direct injection for the online analysis. This additionally resulted in a time gain of approx. an hour for the total fractionation time. Acetonitrile concentrations up to 7.5% do not seem to compromise the chromatographic performance in the online analysis. Using as little as 2 µg digested HeLa lysate, approx. 7000 protein groups could be easily identified with 2 or more unique peptides. This was the case when fractionation was performed at pH 10 as well as at pH 5.5.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 3 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Shu-jing Chen, Kun-ze Du, Jin Li, Yan-xu Chang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A simple and efficient sample preparation method to extract four bioactive compounds (echinacoside, specnuezhenide, oleuropein and nuezhenoside G13) from 〈em〉Ligustri Lucidi Fructus〈/em〉 was established by vortex-forced matrix solid phase dispersion (VFMSPD) method. Chitosan solution was applied as green eluent in this procedure and Celite AZO was employed as dispersant. High performance liquid chromatography (HPLC) equipped with ultraviolet (UV) detector was used to analyze the target analytes. The best result of the investigation was obtained with Celite AZO as dispersant, sample/ dispersant ratio as 1:1, grinding for 2 min, 1 mL high-viscosity chitosan solution (0.5 mg mL〈sup〉−1〈/sup〉) used as the elution reagent and vortex mixing for 1.5 min. The method exhibit a good linearity for the analytes (〈em〉r〈/em〉〈sup〉2〈/sup〉 〉 0.999). The absolute recoveries of the four target compounds in 〈em〉Ligustri Lucidi Fructus〈/em〉 ranged from 90.7% to 98.8% and the relative recoveries of the target compounds ranged from 99.2% to 102% (RSD ≤ 3.4%), which were obtained by the final optimization method. Consequently, the newly developed chitosan solution-based vortex-forced matrix solid phase dispersion (MSPD) combined with HPLC could be efficiently applied to extract and analyze the target compounds in 〈em〉Ligustri Lucidi Fructus〈/em〉 samples.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 7 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Juliana Crucello, Danilo V. Pierone, Leandro W. Hantao〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this article we describe a method using flow-modulated comprehensive two-dimensional gas chromatography with electron capture detector (FM–GC×GC–ECD) for the determination of polychlorinated biphenyls (PCBs) in complex transformer oils bypassing the need for sample preparation. A two-fold improvement in method development was attained. First, the solvation parameter model (SPM) was used to guide column selection. A highly cohesive ionic liquid-based phase (low 〈em〉l〈/em〉 system constant), namely 1,12-di(tripropylphosphonium)dodecane bis(trifluoromethanesulfonyl)imide, was used in the primary stage leading to negligible retention of interfering aliphatic hydrocarbons, which are eluted in the first upper quadrant of the chromatogram. The resulting separation space was used to resolve the critical class of compounds, namely, PCBs and polyaromatic hydrocarbons. Second, a unique combination of column geometries and phase ratios enabled highly efficient reverse fill/flush flow modulation using very low pressure for auxiliary gas flow. The proof of concept method described herein exhibited linearities ranging from 0.990 to 0.994, limits of quantitation (LOQ) from 2.23 and 6.85 µg mL〈sup〉−1〈/sup〉, precision below 5% relative standard deviation (RSD), and accuracy from 84.2% to 108.9% showcasing the potential of FM–GC×GC for routine analysis.〈/p〉〈/div〉

Description: 〈p〉Publication date: 25 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1604〈/p〉 〈p〉Author(s): María B. Anzardi, Juan A. Arancibia, Alejandro C. Olivieri〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Parallel factor analysis 2 (PARAFAC2) is still being advocated for the processing of second-order chromatographic-spectral data, both for qualitative and quantitative applications. However, neither classical PARAFAC2 nor the newly developed flexible non-negative NN-PARAFAC2 version can adequately model these data in a general situation. In quantitative analysis, considerable bias may result in the estimation of analyte concentrations, due to the fact that both PARAFAC2 models apply an artificial constraint to the retrieved profiles, requiring constant cross-product, i.e., constant overlapping, between all pairs of component elution profiles in all samples. This only occurs under limited conditions. In this report, simulations help to understand, visualize and interpret these PARAFAC2 features. Experimental data are also studied concerning the determination of a fluoroquinolone antibiotic in bovine liver samples by liquid chromatography with multi-wavelength fluorescence detection. Both for simulated and experimental data, the PARAFAC2 versions provide poor analytical results, while correct data processing and reasonable analytical indicators can be achieved using multivariate curve resolution - alternating least-squares (MCR-ALS). For the simulated data sets, root mean square errors/relative errors of prediction were 0.01 concentration units/2% for MCR-ALS, compared to 0.02–0.06 units/4–12% for both PARAFAC2 and NN-PARAFAC2. For the experimental data sets, they were 0.025 µg mL〈sup〉−1〈/sup〉/11% for MCR-ALS, 0.09 µg mL〈sup〉−1〈/sup〉/40% for PARAFAC2 and 0.16 µg mL〈sup〉−1〈/sup〉/71% for NN-PARAFAC2, with average recoveries (standard deviation) of 91(14)%, 185(135)% and 69(35)% respectively.〈/p〉〈/div〉

Description: 〈p〉Publication date: 25 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1604〈/p〉 〈p〉Author(s): Petra Ložnjak, Carolina García-Salinas, Rocío Isabel Díaz de la Garza, Anette Bysted, Jette Jakobsen〈/p〉

Description: 〈p〉Publication date: 25 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1604〈/p〉 〈p〉Author(s): Claudia Seidl, David S. Bell, Dwight R. Stoll〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In recent years there has been increasing interest in the use of HILIC separations in two-dimensional liquid chromatography (2D-LC), mainly because the selectivity of HILIC separations complement that of reversed-phase separations for a variety of molecules. Historically, the re-equilibration of HILIC phases following gradient elution has been perceived as too slow to be useful in the second dimension of 2D-LC separations in particular. Recent studies of re-equilibration of HILIC phases by McCalley and coworkers using a limited set of conditions showed that highly repeatable gradient separations could be obtained with re-equilibration times as short as 4.3 min [1], [2]. In this study we aimed to study re-equilibration of HILIC phases under a broader set of conditions, and at much shorter re-equilibration times, in the interest of determining whether or not HILIC separations can be generally considered as a viable option for use in the second dimension of 2D-LC separations. To this end we studied the effects of mobile phase pH, buffer concentration, and preparation method, flow rate, analyte and stationary phase chemistry, column length, and re-equilibration time on retention of a variety of small molecule probe solutes following gradient elution. In general, we have found that excellent separation repeatability can be obtained with quite short (≪10 min) re-equilibration times, even when progress toward full equilibration of the column is quite slow (≫10 min). In other words, even if the stationary phase is not fully equilibrated, as long as it is partially equilibrated in a highly precise manner, highly repeatable retention times can be obtained. Higher flow rate has a positive effect on both the rate of progress toward full equilibration and the repeatability of separation. No significant, consistent effects of eluent pH or buffer concentration on repeatability of gradient separation were observed for the stationary phases studied. Excellent gradient separation repeatability was obtained with shorter columns (30 mm length) with re-equilibration times as short as 3 s. A proof-of-concept 2D-LC separation of several small molecule probes using HILIC separations in both dimensions was performed to illustrate that re-equilibration of these columns can be fast enough for HILIC columns to be considered as a viable option for the second dimension of comprehensive 2D-LC separations.〈/p〉〈/div〉

Description: 〈p〉Publication date: 25 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1604〈/p〉 〈p〉Author(s): Yang Jin, Huawei Lv, Xingchu Gong, Wenyu Sun, Shanshan Zhao, Xiang Wang, Meng Luo, Jizhong Yan, Shengqiang Tong〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The influence of chlorine substituents in chiral separation of three racemic 2-(chlorophenyl)propanoic acids by countercurrent chromatography using hydroxypropyl-β-cyclodextrin as a chiral additive were mainly investigated in the present paper, including 2-(2-chlorophenyl)propanoic acids, 2-(3-chlorophenyl)propanoic acids and 2-(4-chlorophenyl)propanoic acids. The influences of chromatographic conditions on the retention behavior were studied by enantioselective liquid-liquid extraction experiments using the methodology of response surface It was found that 2-(3-chlorophenyl)propanoic acids could be successfully chiral separated by countercurrent chromatography, while no resolution was achieved for racemic 2-(2-chlorophenyl)propanoic acids and 2-(4-chlorophenyl)propanoic acids under optimized separation conditions. The formation of 1:1 stoichiometric inclusion compounds between 2-(3-chlorophenyl)propanoic acids and HP-β-CD was determined by UV spectra measurements. The inclusion constants for 2-(3-chlorophenyl)propanoic acids and HP-β-CD were determined by the Benesi-Hildebrand equation. Meanwhile, the inclusion constants of 2-(3-chlorophenyl)-propanoic acid enantiomer and HP-β-CD were obtained by the pesudophase retention equation in countercurrent chromatography. Furthermore, the inclusion interactions of the three racemates with HP-β-CD were also investigated by the molecular docking. The results obtained from UV spectra measurements and molecular docking showed that the racemate with chlorine substituents in meta-position presented the highest enantiorecognition while the racemates with chlorine substituents in ortho-position had the lowest enantiorecognition. The above results further indicated that forming a stable inclusion complex between racemate and chiral selector is a prerequisite for a successful enantioseparation and at the same time, the difference in inclusion capacity between the two enantiomers is also essential for the enantioseparation.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 4 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Huiying Liu, Nan Li, Xuebo Liu, Yongzhong Qian, Jing Qiu, Xiaoning Wang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Poly(〈em〉N〈/em〉-acryloyl-glucosamine-〈em〉co〈/em〉-methylenebisacrylamide) (poly(AGA-〈em〉co〈/em〉-MBA))-modified Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 nanoparticles were prepared via simple aqueous surface polymerization. The resultant Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉@poly(AGA-〈em〉co〈/em〉-MBA) nanoparticles were used as hydrophilic magnetic solid phase extraction sorbents. Ten aminoglycosides were selected as model analytes to evaluate the extraction performance and mechanism of the sorbents. The prepared magnetic nanoparticles were characterized by Fourier transformed infrared spectroscopy, elemental analysis, a vibrating sample magnetometer, and so on. The sorbents exhibited efficient extraction towards model analytes in hydrophilic interaction chromatography. Only 10.0 mg of sorbent was needed to adsorb analytes from 10.0 mL of a sample solution within a short time (5.0 min). Under optimized conditions, Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉@poly(AGA-〈em〉co〈/em〉-MBA) nanoparticles were applied in the sample preparation for the analysis of 10 aminoglycosides in meat samples by high-performance liquid chromatography-tandem mass spectrometry. The limits of detection (LODs) for the 10 aminoglycosides were in the range of 0.6–23.6 µg kg〈sup〉−1〈/sup〉. Satisfactory recoveries of spiked meat samples from 84.6–98.3% with acceptable relative standard deviations from 3.1% to 7.8% were achieved. Compared to other reported methods for the analysis of aminoglycosides, the present work had comparable or higher sensitivities with a simple extraction procedure. The proposed hydrophilic interaction extraction sorbents are promising as powerful alternatives for extracting and enriching aminoglycosides in animal-derived food samples.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 4 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Yinghe Ji, Zhaorui Meng, Jing Zhao, Hanqing Zhao, Longshan Zhao〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A sensitive, fast, eco-friendly ultrasound assisted liquid–liquid microextraction (LLME) in combination with hydrophobic deep eutectic solvent (DES) method was developed to preconcentrate and extract sulfonamides in fruit juices, prior to high-performance liquid chromatographic (HPLC) analysis. The DES was synthesized with trioctylmethylammonium chloride (TAC) and 2-octanol at the molar ratio of 1:2. Some parameters which affected the extraction efficiency were investigated and optimized, including the volume of DES, extraction method, extraction time, pH. Under the optimum conditions, good linearity (〈em〉r〈/em〉 = 0.9999) in the range of 0.1–50 µg mL〈sup〉−1〈/sup〉 was obtained. The limit of detection (LOD) was 0.02–0.05 µg mL〈sup〉−1〈/sup〉. And the accuracy of the developed method was confirmed by analysis of spike method, the recoveries were in the range of 88.09–97.84% at the spike levels of 2–20 µg mL〈sup〉−1〈/sup〉 in fruit juices.〈/p〉〈/div〉

Description: 〈p〉Publication date: 25 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1604〈/p〉 〈p〉Author(s): Pablo Miralles, Iris van Gemert, Alberto Chisvert, Amparo Salvador〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A new analytical method based on the recently proposed stir bar sorptive-dispersive microextraction (SBSDME) technique has been developed to determine eight hazardous 〈em〉N〈/em〉-nitrosamines in cosmetic products. As previous step, a simple clean-up is carried out with hexane to remove those highly lipophilic compounds that disturb the SBSDME step. Subsequently, SBSDME is performed by using magnetic nanoparticles–metal organic framework composite, CoFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉/MIL-101(Fe), as sorbent to entrap the target analytes, which are later chemically desorbed and measured by liquid chromatography–tandem mass spectrometry (LC–MS/MS). The experimental variables related to the SBSDME procedure were studied to achieve the highest analytical signal. Under the most favorable conditions, the proposed method was validated providing good linearity; enrichment factors up to 62 depending on the analyte; limits of detection from 3 to 13 µg kg〈sup〉−1〈/sup〉; and good repeatability values (RSD 〈 17.0%). Finally, the method was successfully applied to cosmetic samples composed either of lipophilic or hydrophilic matrices. Quantitative relative recoveries (96–109%) were obtained by using standard addition calibration. The present work expands the applicability of the SBSDME technique, whereas its analytical features make it useful to carry out the quality control of cosmetic samples.〈/p〉〈/div〉

Description: 〈p〉Publication date: 25 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1604〈/p〉 〈p〉Author(s): 〈/p〉