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: 21–28 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volumes 1581–1582〈/p〉 〈p〉Author(s): Xuejia Zhang, Qirui Bi, Xingdong Wu, Zhe Wang, Yuanyuan Miao, Ninghua Tan〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Rubiaceae-type cyclopeptides (RAs) are one of characteristic constituents isolated from 〈em〉Rubia〈/em〉 species, which are candidates of innovative anti-tumor drugs due to their significant bioactivity. However, approaches on the systematic characterization and quantification of RAs are still not available because of low contents and complicated purification. In this study, an ultra performance liquid chromatography coupled triple quadrupole tandem mass spectrometry (UPLC-QqQ-MS/MS) method was established and validated for qualitative and quantitative analysis of 14 RAs (〈strong〉1〈/strong〉-〈strong〉14〈/strong〉) in 20 〈em〉Rubia〈/em〉 plants from China. The separation was achieved on a Waters ACQUITY UPLC® BEH C〈sub〉18〈/sub〉 column (50 × 2.1 mm, 1.7 μm) using gradient elution with a mobile phase consisting of 0.1% formic acid in acetonitrile and water. Multiple reaction monitoring (MRM) in positive mode was used to enable the selective detection of RAs from the 〈em〉Rubia〈/em〉 root and rhizome extracts within 10 min. This method was proved to be specific, sensitive, precise, and accurate with the limits of detection and quantification at 0.6–11.4 ng/mL and 1.9–34.2 ng/mL, respectively, and the relative standard deviation (RSD) of the overall intra-day and inter-day precision less than 5.24%. Satisfactory recovery was obtained from 83.80% to 111.77%, with the RSD less than 5.32%. Totally, 67 samples were then qualitatively and quantitatively analyzed by this method and 51 of them were proved to contain RAs. Thereinto, 〈em〉R. podantha〈/em〉 and 〈em〉R. yunnanensis〈/em〉 from Yunnan were the two most abundant species. Additionally, RAs were detected in 8 〈em〉Rubia〈/em〉 species for the first time. Then chemometric approaches were revealed to explain the relationship between samples based on their contents of RAs. This study demonstrated that the method was not only useful for RAs source discovery and chemotaxonomy of 〈em〉Rubia〈/em〉 species, but also could be extended to standardization of RAs medical materials and their new drug research and development.〈/p〉〈/div〉

Description: 〈p〉Publication date: 23 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1577〈/p〉 〈p〉Author(s): 〈/p〉

Description: 〈p〉Publication date: 21–28 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volumes 1581–1582〈/p〉 〈p〉Author(s): Kim Vanderlinden, Gert Desmet, David S. Bell, Ken Broeckhoven〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We report on a systematic study involving columns with a clearly different efficiency (4 distinct quality groups) obtained by packing the columns that were C〈sub〉18〈/sub〉 bonded and endcapped with a different carbon loading. Using B-term analysis (via peak parking) and theoretical models to estimate the magnitude of the C〈sub〉m〈/sub〉- and C〈sub〉s〈/sub〉-term contributions, it could be concluded that the difference in efficiency among the groups was entirely due to a difference in eddy dispersion. As such, the columns provided an ideal testing ground to verify how well the total pore blocking (TPB)-method can be used to probe differences in packing heterogeneity. In agreement with earlier literature observations, it turns out the TPB-method is much more sensitive to packing heterogeneities than the eddy dispersion (H〈sub〉eddy〈/sub〉)-contribution measured under open-pore conditions via B- and C- term subtraction. Typically, differences in H〈sub〉eddy〈/sub〉 on the order of 0.1–0.5μm translate into a difference on the order of 0.5–2μm in the TPB mode. This confirms the TPB as a powerful technique to make very sensitive measurements of the homogeneity of packed beds.〈/p〉〈/div〉

Description: 〈p〉Publication date: 21–28 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volumes 1581–1582〈/p〉 〈p〉Author(s): Roman Jaramillo, Frank L. Dorman〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Thermodynamic retention modeling to a thermally modulated comprehensive two-dimensional gas chromatography (GC × GC) system run under constant flow is performed. Significant errors in modeled second dimension retention time (t〈sub〉r,2〈/sub〉) were observed, in line with past work on thermally modulated GC × GC modeling. A comprehensive study of t〈sub〉r,2〈/sub〉 modeling error for alkane separations across a wide range of heating ramp rates and carrier gas flow rates was performed. Modeling errors were found to be systematic and a function of analyte elution temperature and mobile phase velocity. A model to account for these systematic errors was generated, and associated coefficients were determined which reduced average t〈sub〉r,2〈/sub〉 retention time error in 144 hydrocarbon separations by an order of magnitude resulting in significant improvement in prediction accuracy. The model was used to correct the separation of 139 Grob mix analyte separations, providing an average t〈sub〉r,2〈/sub〉 modeling error of 0.030 ± 0.022 s. The model successfully predicted the separation of n-alkanes on a longer second dimension column configuration.〈/p〉〈/div〉

Description: 〈p〉Publication date: 16 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1576〈/p〉 〈p〉Author(s): 〈/p〉

Description: 〈p〉Publication date: 7 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1579〈/p〉 〈p〉Author(s): Ifeoluwa Idowu, Wesley Johnson, Olga Francisco, Terry Obal, Chris Marvin, Philippe J. Thomas, Courtney D. Sandau, Jörg Stetefeld, Gregg T. Tomy〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Polycyclic aromatic compounds (PACs) consists of multiple compounds and the number of theoretically possible isomers can reach into the thousands. Currently each PAC group is quantified collectively as a single group of compounds. However, individual PACs can reveal important information on how the PACs were formed and this information may be used to determine sources of PACs in environmental samples, It is hypothesized that many of the limitations with characterizing alkylated PACs with one dimensional gas-chromatography (1D GC) can be circumvented using GC × GC (two dimensional gas chromatography). Here we apply comprehensive GCxGC coupled to high-resolution time of flight mass spectrometry (GC × GC-HFTOF-MS) to aid in the separation, identification and quantitation of APACs in three environmental matrices: mussel tissue (〈em〉Mytilus edulis〈/em〉), lubricating oil and coal. In the absence of authentic analytical standards, differences in the mass spectral fragmentation pattern of isomers were used to confirm the identity of isomers within a PAC group. The method was validated according to the EURACHEM guidelines and used to quantify a biological standard reference material (SRM 2974a). The method met all the standard method performance requirements such as trueness, precision and measurement of uncertainty and is fit for quantifying these compounds in biota. Furthermore, the method was used to identify and quantify additional PAC compounds in the SRM 2974a material which to date have not been certified. With appropriate statistical analytical tools, the described GC × GC method can be used as a tool for more robust source fingerprinting and source apportionment of PACs in the environment.〈/p〉〈/div〉

Description: 〈p〉Publication date: 2 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1574〈/p〉 〈p〉Author(s): Xiaolei Zhao, Junying Wang, Junping Wang, Shuo Wang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A water-compatible molecularly imprinted polymer (MIP) was prepared by combining reversible addition-fragmentation chain transfer (RAFT) with reflux precipitation polymerization (RPP) for solid-phase extraction (SPE) coupled with high performance liquid chromatography-tandem mass spectrometry (HPLC–MS/MS) to detect six sulfonamides (SAs) in animal-derived foods and water samples. The SEM images indicated the spherical structure of MIP materials. In water medium, MIPs still performed good specific adsorption for SAs. Under the optimized detection conditions, the proposed method offered good linearity (R〈sup〉2〈/sup〉 〉 0.996) for the six SAs with relative standard deviation (RSD) for ten replicate extractions of 1.64%–4.68%, limits of detection (S/N = 3) of 0.02 μg L〈sup〉−1〈/sup〉-0.1 μg L〈sup〉−1〈/sup〉 and recoveries of 63.49%–115.72%. Besides, the whole extract process avoided organic solvent consumption, and trace sulfadiazine residues were found in the pork sample at similar concentration of 3.57 and 3.79 μg kg〈sup〉-1〈/sup〉 using the MIP-SPE method and commercial Oasis HLB cartridge, respectively. It is confirmed the method could be applied to quantitative detect the trace residue sulfonamides in animal-derived samples and water samples.〈/p〉〈/div〉

Description: 〈p〉Publication date: 30 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1578〈/p〉 〈p〉Author(s): Xue-Bing Wei, Ruo-Qi Li, Han Yu, Ren-Qi Wang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A fast and sensitive ultra–high performance liquid chromatography–electrospray ionization–tandem mass spectrometry (UHPLC–ESI–MS/MS) method was developed for simultaneously analyzing 10 phthalates in perfume, which are forbidden by the hygienic standards for cosmetics in China (2007 edition). Matrix effect is significant on a phthalate when it is co–eluted with other phthalates. Improving the resolution between adjacent phthalate peaks is found effective in reducing the matrix effects. Thus, simultaneous analysis of the 10 phthalates requires successful resolutions of each phthalate. Nonetheless, a trade–off between the resolution and analysis time results either incomplete separation or prolonged analysis time. Here, the UHPLC elution gradient is optimized considering the predicted retention time of each phthalate. The resolutions and matrix effects of targeted compounds are evaluated to determine the optimal elution gradient for UHPLC-MS analysis method. Under the optimized gradient, the resolution between closest phthalate peaks is beyond 1.7, while the analysis time is merely 7 min. Except for dimethyl phthalate (DMP) and dicyclohexyl phthalate (DCHP), insignificant matrix effects have been found on all the phthalates. Direct quantifications through external calibration curve are appropriate for such analytes. Nonetheless, DMP and DCHP suffering obvious matrix effects require extra analyses of spiked samples for the quantifications through the standard addition method. Instrumental limits of quantitation (iLOQs) are 0.12–89 μg L〈sup〉−1〈/sup〉 for the targeted phthalates. Meanwhile, the accuracy and precision of the analytical method are good. Finally, the forbidden phthalates in 26 sampled perfumes are successfully analyzed by the developed method.〈/p〉〈/div〉

Description: 〈p〉Publication date: 26 October 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1573〈/p〉 〈p〉Author(s): 〈/p〉

Description: 〈p〉Publication date: 26 October 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1573〈/p〉 〈p〉Author(s): Xiao-Li Yin, Hui-Wen Gu, Ali R. Jalalvand, Ya-Juan Liu, Ying Chen, Tian-Qin Peng〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The quantification of preservatives in cosmetics has attracted great attentions for their controversial and widespread use. HPLC is a prevailing method for preservatives determination among various analytical methods. However, it takes long time to fully separate these compounds because of the complexity of cosmetic matrices. In this study, a fast and green HPLC-DAD strategy assisted with second-order multivariate calibration methods based on alternating trilinear decomposition (ATLD) and multivariate curve resolution-alternating least squares (MCR-ALS) was developed for the simultaneous determination of eight selected preservatives in complex facial mask samples. This appealing strategy proved to be a useful tool for eliminating unknown interferences in complex matrices without complete separation, which benefited from the “second-order advantages” and thus made the determination of the eight analytes in facial mask samples shorten to 8.2 min under a fast elution program. In particular, for the first time, we focused on the applicability of ATLD method for modeling of HPLC-DAD data with severe signal overlapping and slight time shifts. The spiked recovery values were in the range of 71.4–124.6%, and the RMSEP and REP values ranged from 0.07 to 2.4 μg mL〈sup〉−1〈/sup〉 and 1.3–14.5%, respectively, indicating that the ATLD method could provide satisfactory prediction. The resolved spectral profiles and concentration values were compared with those obtained by the MCR-ALS method, an excellent tool for modeling of data deviating from trilinearity. Both qualitative and quantitative results from the two methods were consistent with each other, which evidenced the competence of ATLD method in handling HPLC-DAD data with severe signal overlapping and slight time shifts.〈/p〉〈/div〉

Description: 〈p〉Publication date: 23 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1577〈/p〉 〈p〉Author(s): Juanjuan Feng, Xiuqin Wang, Yu Tian, Chuannan Luo, Min Sun〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A melamine–formaldehyde (MF) aerogel coating was prepared on basalt fibers (BFs) for in-tube solid-phase microextraction (SPME). MF aerogel-coated BFs were placed in a polyetheretherketone tube to obtain the extraction tube. To build an in-tube SPME–high performance liquid chromatography (HPLC) online system, the extraction tube was connected with HPLC equipment by replacing the sample loop of a six-port valve. The extraction tube was evaluated using eight polycyclic aromatic hydrocarbons (PAHs) as model analytes. After the optimization of important factors, an online analysis method was established. Wide linear ranges (0.03–25 μg L〈sup〉−1〈/sup〉, 0.06–30 μg L〈sup〉−1〈/sup〉) and low detection limits (0.01, 0.02, and 0.05 μg L〈sup〉−1〈/sup〉) were observed. High sensitivity resulted from large enrichment factors ranging from 2070 to 3246. To validate the analysis method, two real water samples were detected. Most of the analytes were not detected in tap water and rainwater, and relative recoveries spiked at 2 and 5 μg L〈sup〉−1〈/sup〉 were in the range of 80%–117%. The extraction repeatability on one tube and the preparation repeatability among three tubes were also tested, and their RSDs (n = 3) were in the range of 0.77%–2.04% and 0.88%–9.17%, respectively. As a result of the high surface area of the MF aerogel and π-π interactions with PAHs, the MF aerogel coating exhibits a superior extraction performance than other SPME materials, including wider linear ranges, lower LODs and higher enrichment factors.〈/p〉〈/div〉

Description: 〈p〉Publication date: 23 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1577〈/p〉 〈p〉Author(s): Milad Ghani, Sayed Mehdi Ghoreishi, Mostafa Azamati〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉The objective of the present study was to develop a simple, sensitive and cost-effective sample pretreatment technique to extract and determine caffeine in different samples of beverage as well as urine. An anodized aluminum bar was electrochemically prepared and employed as nanoporous substrate for in-situ growth of crystals of the zeolitic imidazole framework-67 (ZIF-67). The above-mentioned sorbent, too, was applied as a stir bar sorptive extraction (SBSE) device along with HPLC-UV.〈/p〉 〈p〉Under predetermined experimental condition, the detection limit of the aimed method was 0.05 μg L〈sup〉−1〈/sup〉 in beverages, and it was 0.1 μg L〈sup〉−1〈/sup〉 in urine samples. Moreover, the linear dynamic range was 0.2–200 μg L〈sup〉−1〈/sup〉 for beverages, and it was 0.5–200 μg L〈sup〉−1〈/sup〉 for urine samples, too. The inter-day RSDs (10 μg L〈sup〉−1〈/sup〉) were 5.3% and 5.7% respectively, and they were 5.8% and 6.1% for intra-day RSDs (10 μg L〈sup〉-1)〈/sup〉 in beverages and urine samples. Bar to bar reproducibility for three prepared bars equaled 6.2%. The applicability of the SBSE-HPLC-UV was investigated by determining caffeine in different samples of beverage and urine. The final range of obtained spiking recoveries was from 91.2 to104%.〈/p〉 〈/div〉

Description: 〈p〉Publication date: 2 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1574〈/p〉 〈p〉Author(s): J.A. Navarro-Huerta, J.R. Torres-Lapasió, M.C. García-Alvarez-Coque〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Peak capacity (〈em〉P〈/em〉〈sub〉C〈/sub〉) is a key concept in chromatographic analysis, nowadays of great importance for characterising complex separations as a criterion to find the most promising conditions. A theoretical expression for 〈em〉P〈/em〉〈sub〉C〈/sub〉 estimation can be easily deduced in isocratic elution, provided that the column plate count is assumed constant for all analytes. In gradient elution, the complex dependence of peak width with the gradient program implies that an integral equation has to be solved, which is only possible in a limited number of situations. In 2005, Uwe Neue developed a comprehensive theory for the calculation of 〈em〉P〈/em〉〈sub〉C〈/sub〉 in gradient elution, which is only valid for certain situations: single linear gradients, absence of delays and extra-column effects, Gaussian peaks and constant plate count. Going beyond these limitations implies resolving algebraic expressions that unfortunately cannot be integrated. In this work, 〈em〉P〈/em〉〈sub〉C〈/sub〉 is predicted for multiple situations based on peak simulation. The approach is more general and can be applied for situations out of the scope of the Neue outline, such as complex multi-linear gradients, including asymmetrical peaks. The plots of 〈em〉P〈/em〉〈sub〉C〈/sub〉 versus retention time of the last eluted solute give rise to Pareto fronts, and can be useful for the probabilistic enhancement of peak resolution in situations where complex multi-analyte samples are processed.〈/p〉〈/div〉

Description: 〈p〉Publication date: 26 October 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1573〈/p〉 〈p〉Author(s): Dilrukshika S.W. Palagama, David Baliu-Rodriguez, Apurva Lad, Bruce S. Levison, David J. Kennedy, Steven T. Haller, Judy Westrick, Kenneth Hensley, Dragan Isailovic〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The protocols for solid-phase extraction (SPE) of six microcystins (MCs; MC-LR, MC-RR, MC-LA, MC-LF, MC-LW, and MC-YR) from mouse urine, mouse plasma, and human serum are reported. The quantification of those MCs in biofluids was achieved using HPLC-orbitrap-MS in selected-ion monitoring (SIM) mode, and MCs in urine samples were also quantified by ultra-HPLC-triple quadrupole-tandem mass spectrometry (UHPLC-QqQ-MS/MS) in multiple reaction monitoring (MRM) mode. Under optimal conditions, the extraction recoveries of MCs from samples spiked at two different concentrations (1 μg/L and 10 μg/L) ranged from 90.4% to 104.3% with relative standard deviations (RSDs) ≤ 4.7% for mouse urine, 90.4–106.9% with RSDs ≤ 6.3% for mouse plasma, and 90.0–104.8% with RSDs ≤ 5.0% for human serum. Matrix-matched internal standard calibration curves were linear with R〈sup〉2〈/sup〉 ≥ 0.9950 for MC-LR, MC-RR and MC-YR, and R〈sup〉2〈/sup〉 ≥ 0.9883 for MC-LA, MC-LF, and MC-LW. The limits of quantification (LOQs) in spiked urine samples were ∼0.13 μg/L for MC-LR, MC-RR, and MC-YR, and ∼0.50 μg/L for MC-LA, MC-LF, and MC-LW, while the LOQs in spiked plasma and serum were ∼0.25 μg/L for MC-LR, MC-RR, and MC-YR, and ∼1.00 μg/L for MC-LA, MC-LF, and MC-LW. The developed methods were applied in a proof-of-concept study to quantify urinary and blood concentrations of MC-LR after oral administration to mice. The urine of mice administered 50 μg of MC-LR per kg bodyweight contained on average 1.30 μg/L of MC-LR (n = 8), while mice administered 100 μg of MC-LR per kg bodyweight had average MC-LR concentration of 2.82 μg/L (n = 8). MC-LR was also quantified in the plasma of the same mice. The results showed that increased MC-LR dosage led to larger urinary and plasma MC-LR concentrations and the developed methods were effective for the quantification of MCs in mouse biofluids.〈/p〉〈/div〉

Description: 〈p〉Publication date: 2 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1574〈/p〉 〈p〉Author(s): A. Yanini, F.A. Esteve-Turrillas, M. de la Guardia, S. Armenta〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A new drug trafficking trend has been observed in the last years by the introduction in the black market of new psychoactive substances (NPS) in order to difficult competent authority controls. In this study, ion mobility spectrometry (IMS) and high-resolution mass-spectrometry (HRMS) were proposed as vanguard and rearguard methodologies for the rapid identification of the last generation of NPS in seizures. The combined use of IMS and HRMS has been evaluated through the analysis of 24 NPS seized from 2016 to 2018 in Valencia (Spain) to demonstrate the utility of this approach. The characteristic reduced mobility (K〈sub〉0〈/sub〉) values for seized NPS were determined and mass-mobility relationships were proposed and evaluated for the main NPS families: amphetamine and cathinone derivatives, and synthetic cannabinoids. IMS did not allow a unequivocal identification by itself; so, HRMS analysis was employed as rearguard confirmation methodology for the right identification of NPS. Thus, the combined use of IMS and HRMS can be considered as promising alternative for the rapid screening and identification of NPS in seizures.〈/p〉〈/div〉

Description: 〈p〉Publication date: 23 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1577〈/p〉 〈p〉Author(s): Sebastian Schmidtsdorff, Alexander H. Schmidt, Maria Kristina Parr〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The use of trial-and-error principles is a frequently used technique in method development. This may lead to the fact that analytical methods are used routinely without developers and users having gained extensive and well-founded knowledge about the robustness of their analytical methods and the influence of critical key parameters. This very often leads to unnecessary problems for analysts. A simple way in reverse phase chromatography to simulate the effects of pH value changes on the separation and retention of substances is the pH-dependent calculation of the logD value. With this tool, model substances were used to show how the time requirement for method screening can be considerably reduced 〈em〉in silico〈/em〉 and, in addition, extended knowledge about the separation mechanics can be generated. Based on this knowledge, a new method for the purity analysis of carbamazepine was developed within a very short period of time, which improves the performance of the official Ph.Eur. monograph by far. Furthermore, the extremely high robustness of the new method was demonstrated. Using the logD based approach, Quality-by-Design is applied in method development and kept pace with the increasing requirements of regulatory authorities in the pharmaceutical industry.〈/p〉〈/div〉

Description: 〈p〉Publication date: 23 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1577〈/p〉 〈p〉Author(s): Xin Zheng, Xinge Cui, Huaidong Yu, Ji Jiang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Photodynamic therapy (PDT) has been accepted as an alternative treatment for cancer, and its target specificity can be achieved by controlling the location at which light activates the photosensitizer. Photocyanine, a novel anticancer phthalocyanine-based photosensitizer, is a mixture of 4 cis-isomers of a series of synthetic products, and accordingly, it is essential to verify whether there are differences in pharmacokinetics among the four isomers for clinical application, which requires reliable analytical methods to measure the plasma concentrations of the four isomers.〈/p〉 〈p〉An efficient LC–MS/MS method coupled with differential mobility spectrometry (DMS) for the simultaneous quantification of the four photocyanine isomers in human plasma was developed and validated herein. This method had a limit of quantification of 10 ng mL〈sup〉−1〈/sup〉 for each isomer and showed stable and reproducible inter- and intra-day results. Use of this method in preliminary pharmacokinetic studies in patients with esophageal cancer showed that the exposure and distribution of the four isomers were different, which had not been found in previous studies.〈/p〉 〈p〉The present research revealed that DMS was an effective tool for isomeric quantitation and that LC-DMS-MS/MS presented robust and reliable in biomatrix analysis. The method significantly improved peak separation and sensitivity compared with that of other LC–MS-based methods.〈/p〉 〈/div〉

Description: 〈p〉Publication date: 30 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1578〈/p〉 〈p〉Author(s): Corentin Berardet, Julia Kaffy, Sandrine Ongeri, Myriam Taverna〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Type 2 diabetes is characterized by the aggregation of human Islet Amyloid Polypeptide (hIAPP) from monomer to large and insoluble fibrils. According to several recent studies, small soluble oligomers are now considered as potential toxic species. No monitoring tool has been to date reported to mimic 〈em〉in vitro〈/em〉 the oligomerization process of hIAPP over time, although this would allow selecting candidate compounds that slow down or stop this pathological process. Considering the poor stability of those species and the necessity to monitor in real time, a compatible with the monitoring of hIAPP oligomerization CE method coupled to UV detection was developed. Three groups of hIAPP oligomers/monomers formed during this process could be separated. A polybrene coating was used to avoid adsorption of hIAPP onto capillary walls. Peaks identification was performed using a combination of CE-MS, filtrations and SDS-PAGE. They revealed that one peak is composed of monomer with a very small amount of dimer and trimer, whereas the two others are composed of bigger species higher than 100 kDa. We demonstrated that this real time oligomerization process started from the very initial step, with hIAPP principally as a monomer, until the formation of very big oligomers. This method was shown to be repeatable with RSDs on electrophoretic mobilities and relative peak areas less than 1.6 and 5.8% respectively for the monomer peak. Its application to study the anti-aggregation properties of resveratrol showed that this compound saved more than 30% of the monomeric hIAPP form whereas it almost disappeared without. The method opens new perspectives for the screening of potential drugs for type 2 diabetes.〈/p〉〈/div〉

Description: 〈p〉Publication date: 26 October 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1573〈/p〉 〈p〉Author(s): E. Hakme, A. Lozano, S. Uclés, M.M. Gómez-Ramos, A.R. Fernández-Alba〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Spices are known as difficult matrices that contain variable amounts of fats, piperine or many other matrix constituents. The increasing sensitivity of new GC–MS/MS platforms opens new approaches to analyze pesticide residue in complex matrices such as spices, by sample dilution. The aim of this work is to develop and validate an effective multiresidue method for the analysis of pesticide residues in spices by GC–MS/MS. In this paper, we highlight the importance of reducing matrix interferences generated from co-extractive components of spices. Moreover, we emphasize the concern of obtaining clean extracts requiring less instrument maintenance. By evaluating the total ion chromatograms (TIC) on GC-Orbitrap-MS of different extracts using various sorbents, QuEChERS citrate using EMR-Lipid sorbent resulted in the cleanest extract among Z-Sep, Primary secondary amine (PSA), Oasis〈sup〉®〈/sup〉 Prime HLB, and Supelclean〈sup〉™〈/sup〉 Ultra cartridges that consist of a top bed of PSA, C18 and Grashsphere〈sup〉™〈/sup〉 2031 and a bottom bed of Z-Sep. Later, the analyses were performed on a GC-QQQ-MS/MS, applying a 15 min runtime method covering 205 compounds. The samples were diluted 25 times before the injection bearing in mind that the instrumental LOQs reached (〈sub〉i〈/sub〉LOQ) were 2 ng g〈sup〉−1〈/sup〉 and the method LOQs (mLOQ) were 50 ng g〈sup〉−1〈/sup〉. Good recoveries between 70 and 120% with RSDs lower than 20% were observed for 90% of the compounds in black pepper and for 83% of the compounds in cayenne pepper. To demonstrate the applicability of the proposed method, 50 real dried and non-dried spice samples were analyzed. The most detected pesticides were metalaxyl, chlorpyrifos, tebuconazole, ethion, and chinomethionate.〈/p〉〈/div〉

Description: 〈p〉Publication date: 2 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1574〈/p〉 〈p〉Author(s): 〈/p〉

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: 30 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1578〈/p〉 〈p〉Author(s): Arch Creasy, Joseph Lomino, Giorgio Carta〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The gradient elution hydrophobic interaction chromatography of a monoclonal antibody that exhibits U-shaped retention as a function of the ammonium sulfate concentration is investigated for overloaded conditions at protein loads up to 30% of the column equilibrium binding capacity. Protein load and gradient slope affect both elution peak shape and protein recovery during the gradient. Higher protein loads result in tailing peaks with near 100% recovery that transition to fronting peaks and incomplete recovery as the protein load is reduced. The gradient slope also affects peak shape and recovery. Tailing peaks with lower recovery are obtained with sharper gradients and the most tailing peak and lowest recovery are obtained when step elution rather than gradient is implemented. Modeling the chromatographic elution based on independently determined adsorption isotherms as a function of protein and ammonium sulfate concentration predicts results in agreement with the experimental trends confirming that the unusual chromatographic behavior observed is due to the U-shaped protein binding as a function of the ammonium sulfate concentration. Although less pronounced than in the dilute limit, the U-shaped binding still produces peak shapes and recovery losses as a function of gradient slope that differ from those seen for systems where retention is a monotonic function of salt concentration.〈/p〉〈/div〉

Description: 〈p〉Publication date: 30 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1578〈/p〉 〈p〉Author(s): Emanuela Pietropaolo, Roberta Albenga, Fabio Gosetti, Valentina Toson, Sander Koster, Maricel Marin-Kuan, Julien Veyrand, Amaury Patin, Benoît Schilter, Alessandro Pistone, Lorenzo Tei〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Polyester can coatings protect both food and packaging from mutual contamination. Even though, can coatings may release Non-Intentionally Added Substances (NIAS) in addition to Intentionally Added Substances (IAS). As NIAS are mainly constituted by cyclic or linear side products that are formed during the polymerization process, we focused our attention on these oligomeric species of molecular weight 〈1000 Da. These oligomers were obtained from two different polyester resins, each synthesized from four monomers (two phthalic acids and two diols), and from the corresponding final enamel can coatings using ethanol at 95% and 50% at 60 °C for 4 h and 10 days, respectively, as food simulants. HPLC-ESI-MS analysis on the extracts allowed identifying various cyclic and linear oligomers. For the conclusive identification of the different oligomers and their isomeric structures, ad hoc standards were synthesized by acylation reaction between alkyl diols and phthaloyl chlorides. By comparison of 〈sup〉1〈/sup〉H NMR spectra, linear and cyclic oligomers were characterized by finding the major presence of 2 + 2 cyclic compounds. The 16 synthesized standards, 4 linear and 12 cyclic compounds were used to establish a method for quantification of linear and cyclic oligomers in enamel migration samples by micro HPLC-high-resolution MS (HRMS). The results showed no significant differences between the amounts of cyclic oligomers extracted with both ethanol concentrations (50 and 95%) and time contact. The extracts showed only a small amount of linear compounds and a prevalence of 2 + 2 cyclic oligomers. The work shows the great importance of the synthesis of specific standards to allow exact quantification in food contact material migrates.〈/p〉〈/div〉

Description: 〈p〉Publication date: 23 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1577〈/p〉 〈p〉Author(s): Marta Gładysz, Małgorzata Król, Patryk Własiuk, Michał Piwowar, Grzegorz Zadora, Paweł Kościelniak〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, the effective and robust 〈em〉semi〈/em〉-destructive ultrasound assisted extraction (UAE) method followed by gas chromatography coupled to mass spectrometry (GC–MS) method used for analysis of red lipsticks samples was developed, optimized and evaluated. 43 red lipsticks of a very similar hue representing of 21 different manufacturers were investigated. The red lipsticks (approximately 0.05 mg) were applied on a disc (of ø 2 mm) placed on specially designed stand printed with a 3D printer. In order to optimize the main factors affecting extraction process, Doehlert experimental design with response surface methodology was applied. The optimal for all analysed lipsticks UAE extraction conditions were: 21 min – time, 35 °C – temperature of the ultrasonic bath, and the 100 μL of extraction mixture of acetonitrile, methanol and acetone (50:30:20,  v/v/v). The developed, qualitative UAE/GC–MS method was evaluated and then successfully used for the differentiation of 43 red lipsticks. In this case, the two approaches were utilized: the visual inspection of chromatograms and the likelihood ratio model. The results confirmed that the proposed method has a great potential in lipsticks differentiation and after adaptation to real samples it seems to be a good alternative to the methods routinely used in forensic science investigations.〈/p〉〈/div〉

Description: 〈p〉Publication date: 23 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1577〈/p〉 〈p〉Author(s): Weijia Zhou, Jixia Wang, Yaopeng Zhao, Long Yu, Ye Fang, Hongli Jin, Han Zhou, Pengyu Zhang, Yanfang Liu, Xiuli Zhang, Xinmiao Liang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Traditional Chinese Medicines (TCMs) have been widely used in clinical practice, and provided a rich source for discovering new drug leads. However, efficient identification of active molecules responsible for the therapeutic effects of complex TCMs is still highly challenging. Here, we combined label-free cell phenotypic assay with two dimensional liquid chromatography (2DLC) to identify potential β〈sub〉2〈/sub〉-adrenoceptor 〈strong〉(〈/strong〉β〈sub〉2〈/sub〉-AR) agonists related to anti-asthmatic effect of 〈em〉Curcuma zedoaria Rosc〈/em〉 (〈em〉C.zedoaria〈/em〉), a commonly used TCM. The ethyl acetate extract of 〈em〉C.zedoaria〈/em〉 was first fractionated into 26 fractions. Label-free cell phenotypic profiling was then used to locate the active sites. Orthogonal second-dimensional (D2) separation was performed on two fractions displaying agonistic effect at the β〈sub〉2〈/sub〉-AR, combined with screening of the D2 fractions to track the activity. Finally, this approach led to the isolation of three known diarylheptanoids, among which diarylheptanoid 〈strong〉b〈/strong〉 exhibited the most potent agonistic activity with an EC〈sub〉50〈/sub〉 value of 5.93 μM. This result was further demonstrated through the chemical synthesis of diarylheptanoid 〈strong〉b〈/strong〉. It is the first time to discover that diarylheptanoids could activate the β〈sub〉2〈/sub〉-AR, which may be responsible for the anti-asthmatic effect of 〈em〉C.zedoaria〈/em〉 observed traditionally and in clinical application. This study also demonstrates the potential of this integrated strategy for identifying active ingredients and determining the basis of therapeutic materials in complex TCMs.〈/p〉〈/div〉

Description: 〈p〉Publication date: 14 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1580〈/p〉 〈p〉Author(s): Hoon Choi, David Harvey, Yi Ding, Nien-Hwa Linda Wang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A constant-pattern design method for separating ternary mixtures using ligand-assisted displacement chromatography was developed for non-ideal systems. The general correlation for the minimum column length required to achieve the constant–pattern state for binary separations from our previous study was extended to ternary separations. Additionally, an equation for the yield of a target component as a function of key dimensionless groups was derived based on the constant-pattern mass transfer zone lengths. The column length and operating velocity solved from the two equations ensured the yields and the constant–pattern state for the target components. A selectivity weighted composition factor was developed to allow the design method to specify a minimum target yield for one or multiple components. The design method was verified using simulations and experiments for different targeted yields (70–95%), ligand concentrations (0.03–0.06 M), and feed compositions (1/12–5/6). The targeted yields were achieved or exceeded in all cases tested. The minimum column length required to achieve a constant pattern-state and the productivity of LAD are limited by the lowest selectivity or by a minority component with a low concentration in the feed, even when it does not have the lowest selectivity. Sacrificing the yields of minor components can increase the total productivity significantly. The productivities achieved using this design method are 839 times higher than literature results for ternary separations with the same purity and similar yields.〈/p〉〈/div〉

Description: 〈p〉Publication date: 30 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1578〈/p〉 〈p〉Author(s): Xiaohui Yan, Yingying Zhan, Dongdong Zhong, Yanshuo Li, Dapeng Wu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Solid-phase microextraction (SPME) coupled with thermal desorption-gas chromatography (TD-GC) has become a powerful analysis tool for volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs) in water samples. However, water adsorption into polar microextraction phase is usually unavoidable during the extraction process, and the burst of large amounts of water vapour during thermal desorption will cause serious problems to GC separation and detectors. Pawliszyn’s group had demonstrated that the tens of micron-thick, defect-free polydimethylsiloxane (PDMS) coating could act as a perfect barrier for water adsorption and offer much better compatibility in complex matrices. However, the PDMS overcoat largely decreased the uptake rate of polar analytes into the inner sorbent. In order to quantify the effect of PDMS coating thickness on water adsorption amount and the extraction kinetics, ultrathin PDMS layer was used to coat the polar extraction phase with polyimide (PI) as a model in this work. It was surprising to find that the PDMS coating with the thickness less than one micron can decrease the water adsorption by 96%, while the extraction efficiency for polar analytes (phenolic compounds and nitroaromatic explosives) was decreased by less than 20% at the extraction time of 30 min. Moreover, the kinetic data showed that the thinner the PDMS coating was, the less the uptake rate of polar analytes into PI extraction phase decreased. Finally, polar poly (phthalazine ether sulfone ketone) (PPESK) extraction phase was also coated with ultrathin PDMS coating to verify the universality of the strategy. Generally, the water adsorption problem in polar SPME was overcome to a great extent, and the extraction efficiency of polar analytes was mainly preserved with this ultrathin PDMS coating, which could broaden the application of SPME in the environmental field.〈/p〉〈/div〉

Description: 〈p〉Publication date: 16 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1576〈/p〉 〈p〉Author(s): Philippe Vervliet, Siemon de Nys, Imke Boonen, Radu Corneliu Duca, Marc Elskens, Kirsten L. van Landuyt, Adrian Covaci〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Since 2011, the World Health Organization has encouraged a global phase-down of the use of dental amalgam and actively supported the use of alternative, resin-based dental materials. The resins consist of (meth)acrylate monomers derived from Bisphenol A (BPA), such as Bisphenol A glycidyl methacrylate (BisGMA) and Bisphenol A ethoxylate methacrylate (BisEMA) or triethylene glycol dimethacrylate (TEGDMA) and urethane dimethacrylate (UDMA) which lack the BPA backbone. Besides monomers, other compounds such as photoinitiators and stabilizing agents can be present in the dental resin matrices. The current study consists in the development of an analytical method for the separation and identification of dental material components using LC-QTOF-MS. The developed method was applied on several dental material ingredients, unpolymerized composite resins, and a common dental sealant. The acquired high resolution accurate-mass data was analyzed using suspect screening with an in-house developed library. Next to the main components, various isomers and impurities related to the production of the main component have been detected and identified in the dental material ingredients. In total, 39 chemicals have been identified in the analyzed dental materials. On average 15 chemicals have been identified. Major components, such as BisEMA, BisGMA and TEGDMA were identified although they were not always stated in the material safety data sheets. Minor components included photoinitiators, such as ethyl 4-dimethyl aminobenzoate (EDMAB) and (meth)acrylates impurities originating from production of main ingredients.〈/p〉〈/div〉

Description: 〈p〉Publication date: 9 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1575〈/p〉 〈p〉Author(s): p-Shiqian Gao, Yutong Guo, Xinyue Li, Xuedong Wang, Junxia Wang, Feiyue Qian, Haidong Gu, Zhanen Zhang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A magnetic nano-adsorbent material was prepared by functionalizing carboxylic group onto the granule surface of magnetic graphene oxide nanoparticles (CMGO), using in-situ co-precipitating method. The surface morphology was characterized by SEM and TEM. The CMGO was selected as the adsorbent for the magnetic solid phase extraction (MSPE) of sulfonamides (SAs) from environmental water samples, and the eluted analytes were determined by ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). A series of experimental parameters were optimized to improve the extraction efficiency such as amount of CMGO, extraction time, pH, ionic strength of the sample solution and desorption conditions. When the pH of water sample was 4.00, the extraction recoveries (ERs) for SAs were over 82.0% with 15.0 mg CMGO adsorption for 20 min. Under the optimized extraction conditions, linear range was obtained with coefficients of determination (R〈sup〉2〈/sup〉)≥0.9983. The limits of detection for this proposed method were in the range of 0.49–1.59 ng/L, and the enrichment factors were 1320-1702 for eight SAs. The newly developed method was successfully applied to the analysis of trace SAs in real-world water samples, which provided satisfactory ERs in the range of 82.0–106.2% with RSDs less than 7.2%. Overall, it shows a great potential for the concentration of trace amine organic pollutions in complex matrices.〈/p〉〈/div〉

Description: 〈p〉Publication date: 2 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1574〈/p〉 〈p〉Author(s): E. Lesellier, C. West〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Many different sorts of bonded phase chemistries may be used in high-performance liquid chromatography (HPLC) in the reversed-phase mode: C8, C18 (type A or B), polar-embedded C18, phenyl, pentafluorophenyl, or cyanopropyl. To assess their retention and selectivity properties, chromatographic tests exist. The data obtained from these tests may be presented in three ways. First, simple classification diagrams may be plotted, when only two or three parameters are studied. Secondly, chemometric treatments such as principal component analyses (PCA) or hierarchical cluster analyses (HCA) may be computed, when at least 4 parameters are studied. These are sometimes uneasy to interpret. Thirdly, the “distance” between one column and a reference column may be estimated, through calculated ranking (〈em〉F〈/em〉 or CDF) or selectivity (〈em〉s〈/em〉) factors.〈/p〉 〈p〉In this paper, another treatment type is applied to the data of Euerby (Tanaka test) and Snyder (Hydrophobic Subtraction Model), each of these tests having 6 parameters. This treatment produces a visual classification, called spider diagram. In the first part of this series, this type of classification was applied to the classification of solvents. A logical and easily comprehensible classification is obtained for the varied types of bonded phases, with a clear location, which can be related to the chromatographic properties. The comparison of these diagrams shows that the classification based on Snyder’s hydrophobic subtraction model discriminates the stationary phases more effectively than the one based on the Tanaka test.〈/p〉 〈p〉Finally, on the basis of the parameter relevance and in order to favour comparison between these two tests and a third one called the carotenoid test, simplified classification maps are proposed. For Tanaka test, the selected parameters are the pentylbenzene retention factor (hydrophobicity), the benzylamine/phenol separation factor at pH 7.6 (polar surface activity) and the triphenylene/〈em〉ortho〈/em〉-terphenyl (shape selectivity) separation factor. For Snyder test, the parameters selected are the ethylbenzene retention factor (hydrophobicity) the 〈strong〉C〈/strong〉 term at pH 7.0 (polar surface activity) and the 〈strong〉S*〈/strong〉 term (steric electivity). The location of some stationary phases onto the maps and their rankings are compared and shown to agree well between the three tests.〈/p〉 〈/div〉

Description: 〈p〉Publication date: 23 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1577〈/p〉 〈p〉Author(s): Matthew Giardina, James D. McCurry, Pascal Cardinael, Gaëlle Semard-Jousset, Chiara Cordero, Carlo Bicchi〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The development of the reversed fill/flush modulator represents a significant advancement in flow-modulated, comprehensive two-dimensional gas chromatography (GC × GC). Compared to the forward flush/fill modulator, the reversed-flow modulator is less susceptible to baseline anomalies and peak tailing as a result of modulator channel overfilling or insufficient purging of high concentration analytes. Flow reversal requires the addition of a bleed capillary not present in the forward-flow modulator. Selecting the appropriate restriction of the bleed capillary is critical. If the bleed capillary is too restrictive, eluate from the first-dimension column can split between the modulator channel and second-dimension column, which also results in baseline artifacts. To gain a better understanding of the reversed-flow modulator, a comprehensive pneumatic model was developed. The model was validated by comparing calculated and measured hold-up times. The errors in calculated hold-up times were less than 1% of the measured values. The model can be used to predict first-dimension eluate splitting and determine the optimal bleed capillary dimensions to prevent its occurrence. Calculation of the modulator hold-up time can be used to determine the maximum collection time to ensure comprehensive analysis and optimal flush times for partial fill operation.〈/p〉〈/div〉

Description: 〈p〉Publication date: 2 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1574〈/p〉 〈p〉Author(s): Colin T. Mant, Andrew Byars, Sean Ankarlo, Ziqing Jiang, Robert S. Hodges〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We are currently examining the potential of amphipathic cationic α-helical peptides as a new generation of peptide standards for both cation-exchange high-performance liquid chromatography and reversed-phase chromatography. Thus, amphipathic peptides are particularly suitable for high-performance liquid chromatography standards due to the preferred binding of the non-polar face to the hydrophobic stationary phase of reversed-phase packings or the preferred binding of the polar face to the charged/hydrophilic stationary phase of cation-exchange packings. The ability of different reversed-phase or cation-exchange matrices to separate mixtures of peptide standards with only subtle hydrophilicity/hydrophobicity variations in both the non-polar and polar face of the peptides can then be assessed. Currently, we have designed 〈em〉de novo〈/em〉 a mixture of six 26-residue all D-conformation amphipathic cationic α-helical peptides with a single, positively charged lysine residue in the center of the non-polar face and an increasing number of lysine residues (4–9 residues) replacing neutral residues in the polar face, resulting in an overall net positive charge of +5 to +10. Thus, the non-polar, preferred reversed-phase chromatography binding face remains constant, with only the polar face varying in hydrophilicity/hydrophobicity. Interestingly, even with the non-polar face remaining constant, reversed-phase columns of varying functional group properties (e.g., C〈sub〉8〈/sub〉, C〈sub〉18〈/sub〉, phenyl, polar endcapped, polar embedded) and porosity (porous versus superficially porous) were able to separate the six peptides in 〈em〉aq.〈/em〉 TFA/acetonitrile gradients, albeit with different selectivities. The value of the standards in cation-exchange chromatography was expressed by monitoring the requirement of acetonitrile (0–40% in the mobile phase) to overcome hydrophobic interactions of the peptides with the cation-exchange matrix matrix when eluting with sodium perchlorate gradients at pH 6.5. Interestingly, the resolution of the higher charged peptides (+8,+9,+10) was particularly sensitive to acetonitrile levels. Our results clearly demonstrate the excellent potential of these novel peptide standards to enable optimal column choice and mobile phase conditions for reversed-phase chromatography and cation-exchange chromatography for peptide separations.〈/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: 30 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1578〈/p〉 〈p〉Author(s): Yinhui Yang, Meiling Qi, Jinliang Wang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This work describes the separation performance of a star-shaped truxene-based material (denoted as EDOTT) as the stationary phase for capillary gas chromatography (GC). The EDOTT capillary column achieved the column efficiency of 5920 plates/m by 〈em〉n〈/em〉-dodecane, 4890 plates/m by naphthalene and 3960 plates/m by 1-octanol at 120 ℃. Its selectivity and retention behaviour were investigated by a number of mixtures of diverse analytes and their isomers. As a result, it showed advantageous performance for separations of apolar to polar analytes, especially phenols and alcohols, over its analogous TTT, TDT and TFT stationary phases. In addition, the EDOTT capillary column was investigated for its column loadability, repeatability and thermal stability, and was finally applied for the determination of isomer impurities in real samples. This work provides an alternative truxene-based stationary phase with high selectivity for polar analytes and demonstrates the key role of structural modification in developing a family of stationary phases with specific selectivity for targeted analytes.〈/p〉〈/div〉

Description: 〈p〉Publication date: 9 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1575〈/p〉 〈p〉Author(s): Roger Sheu, Aurelie Marcotte, Peeyush Khare, Sophia Charan, Jenna C. Ditto, Drew R. Gentner〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Gas-phase organic compounds across a range of volatilities, including volatile organic compounds (VOCs), are key components of outdoor air, indoor spaces, and a variety of other anthropogenic and biogenic systems. The collection of offline samples on adsorbent-packed tubes for analysis on laboratory instrumentation has been in use for decades, but with limited sensitivities and compound coverage. We present and evaluate our integrated sampling-to-analysis system that enables offline detailed chemical characterization of multi-faceted organic mixtures at trace concentrations. Its capabilities extend across a diverse variety of VOCs with different molecular features, as well as intermediate and semivolatile organic compounds (I/SVOCs). Samples can be collected manually or via automated devices that have been applied in chamber, field, and aircraft platforms. The laboratory instrumentation can be coupled to both a high resolution mass spectrometer (MS) and a traditional quadrupole MS, though performance metrics presented in this study are determined via the traditional MS. We demonstrate capabilities for detailed chemical characterization and routine performance for a wide range of compound functionalities at sub-part per trillion (ppt) concentrations, and as low as 〈100 parts per quadrillion (ppq), yielding 3300 observed unique compound peaks in a single indoor air sample. These limits of detection and compound coverage were accomplished through a holistic optimization of the entire system and lifecycle of adsorbent tubes. We present our best practices for all aspects of tube production, handling, sampling, and analysis, and an examination of commercially-available materials and our custom adsorbent tubes using a diverse mix of VOC, IVOC, and SVOC standards, including difficult to measure analytes across a range of polarities and functionalities. In many aspects, the commercially-available materials and tube conditioners tested were insufficient for achieving low-ppt measurements.〈/p〉〈/div〉

Description: 〈p〉Publication date: 16 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1576〈/p〉 〈p〉Author(s): Milla M. Leppä, Maarit Karonen, Petri Tähtinen, Marica T. Engström, Juha-Pekka Salminen〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, a semipreparative liquid chromatography method was developed for the isolation of chemically well-defined proanthocyanidin (PA) oligomer and polymer fractions. The aim was to achieve better separation than traditionally achieved for the PAs with other chromatographic methods. The method was tested with eleven PA rich Sephadex LH-20 fractions, which originated from eleven different plant species. The resulting semipreparative fractions were analyzed by both triple quadrupole and high-resolution mass spectrometry assisted by ultrahigh-performance liquid chromatography (UPLC) separation. The results showed remarkable differences in the procyanidin to prodelphinidin ratio, mean degree of polymerization, and specific oligomeric and polymeric content. However, some of these features indicated consistent patterns between species as the function of UPLC retention time. The developed method enables the production of tens of well-defined fractions of PA oligomers and polymers from the unresolved chromatographic PA hump. Accordingly, this allows researchers to explore the most bioactive parts of the complex PA humps of any plant species, which have not been possible earlier.〈/p〉〈/div〉

Description: 〈p〉Publication date: 14 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1580〈/p〉 〈p〉Author(s): Mark R. Schure, Robert S. Maier〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Ellipsoidal particles are investigated as packing media for liquid chromatography using high resolution fluid mechanics and Brownian dynamics simulations. The simulations are conducted with packed capillary columns, as well as beds with periodic boundary conditions (PBCs) to study transport in the absence of wall effects. The performance of ellipsoidal particles is evaluated over a range of aspect ratios. The definition of effective diameter used to compare sphere and ellipsoidal particle performance metrics is presented and discussed along with scaling relationships which are necessary to compare sphere and ellipsoidal particle packs.〈/p〉 〈p〉Ellipsoidal particle packs are found to be inferior to sphere packs using PBCs to study chromatographic dispersion. The separation impedance was calculated with PBCs and shown to be approximately the same with ellipsoidal particles as those of spheres. Efficiency of ellipsoidal packs, as measured by plate height, is lower than spherical particle packs and the pressure drop is higher than sphere packs when using PBCs.〈/p〉 〈p〉However, a smaller wall effect is shown for ellipsoidal particles when packing cylindrical capillaries. Radial variations in packing porosity and in flow within the wall region are smaller for ellipsoidal packings. The minimum reduced plate height and the separation impedance for the packed capillaries clearly demonstrate the advantages of ellipsoidal particles compared to spherical particles. This predicted performance advantage remains to be demonstrated in actual practice.〈/p〉 〈/div〉

Description: 〈p〉Publication date: 30 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1578〈/p〉 〈p〉Author(s): Tianyu Ma, Hongjing Dong, Heng Lu, Hengqiang Zhao, Lanping Guo, Xiao Wang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Caffeoylquinic acid derivatives exhibit anti-inflammatory, antioxidant, and antibacterial activities. We successfully applied pH-zone-refining counter-current chromatography (pH-ZRCCC) to separation of isomeric caffeoylquinic acids from 〈em〉Lonicerae japonicae〈/em〉 Flos using a two-phase solvent system composed of ethyl acetate–〈em〉n〈/em〉-butanol–acetonitrile–water (3:1:1:5, v/v/v/v). Trifluoroacetic acid (10 mM) was added to the upper phase as a retainer and ammonium hydroxide (10 mM) was added to the lower phase as an eluter. As a result, 167.8 mg of chlorogenic acid, 15.9 mg of isochlorogenic acid B, 103.4 mg of isochlorogenic acid C, and 156.0 mg of isochlorogenic acid A were obtained from 1.2 g of crude extract, and all compound purities were over 96%. In addition, by comparing the numeric values of partition coefficient of compounds, it was found that larger differences between the 〈em〉K〈/em〉 values of adjacent compounds in the solvent systems resulted in higher sample loading capacities. pH-ZRCCC method is an efficient preparative separation of isomeric caffeoylquinic acids from natural products.〈/p〉〈/div〉

Description: 〈p〉Publication date: 9 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1575〈/p〉 〈p〉Author(s): Sofia C. Vardali, Victoria F. Samanidou, Yannis P. Kotzamanis〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A UPLC-QTOF-MS method for the simultaneous determination of 20 veterinary drug residues and metabolites (tetracyclines, quinolones, sulfonamides and diaminopyrimidines) in edible muscle plus skin tissue of European sea bass (〈em〉Dicentrarchus Labrax〈/em〉) was developed. For the identification of analytes a positive electrospray ionization quadropole time-of flight mass spectrometer operating in MS〈sup〉E〈/sup〉 mode (UPLC-QTOF-MS〈sup〉E〈/sup〉) was used. MS〈sup〉E〈/sup〉 mode provides high chromatographic resolution and accurate mass measurements in both MS and MS/MS modes simultaneously in a single run. Separation was achieved on a UPLC BEH C18 (50 mm × 2.1 mm, 1.7 μm) column in a gradient elution program of 10 min. Examined antibiotics were isolated easily after a simple solid-liquid extraction procedure with acidic acetonitrile (0.1% v/v formic acid) and Na〈sub〉2〈/sub〉EDTA 0.1 M. Recovery rates from muscle plus skin tissue ranged from 93.8% to 107.5% for all targeted compounds. The detection limits and the limits of quantification ranged from 2.22 to 15.00 μg/kg, and from 6.67 to 45.46 μg/kg, respectively. The developed method was validated in terms of selectivity, matrix effect, linearity, accuracy, precision, stability and sensitivity, CCα and CCβ according to European Union Decision 2002/657/EC. The proposed method was applied for the analysis of contaminated fish samples after in feed administration of danofloxacin mesylate.〈/p〉〈/div〉

Description: 〈p〉Publication date: 9 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1575〈/p〉 〈p〉Author(s): Heyong Cheng, Wenwen Zhang, Yuanchao Wang, Jinhua Liu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Metal speciation analysis of microsamples in the clinical, biological and forensic fields is important for elucidating the metals’ toxicity, mobility and metabolic behaviors of metals. Such analysis may be achieved by nanoliter high-performance liquid chromatography (nanoHPLC) hyphenated with inductively coupled plasma mass spectrometry (ICP-MS). In this work, an in-column high-pressure nebulizer (ICHPN) was developed to enhance the sensitivity and the separation efficiency of the sheathless nanoHPLC-ICP-MS coupling. The ICHPN consists of two concentric fused-silica capillaries with tapered tips connected 〈em〉via〈/em〉 a PEEK tee, where C〈sub〉18〈/sub〉 silica particles with a size of 5 μm were packed in the tapered inner capillary based on the keystone effect. Combining a heated single pass spray chamber with a makeup gas, the ICHPN was capable of independently optimizing the nebulization efficiency and the transport efficiency. The ICHPN offered high sensitivities, low detection limits and good precision at nanoflow rates. Compared with commercial nebulizers, the ICHPN fabrication was simple, rapid, reproducible and inexpensive. By implementing the ICHPN, we achieved rapid separation of four mercury species, 〈em〉i.e.〈/em〉, Hg〈sup〉2+〈/sup〉 and methyl-, ethyl- and phenylmercuric chloride, within 8.0 min with good resolution (2.0–13.9). Detection limits of 0.044-0.13 μg L〈sup〉−1〈/sup〉 were obtained with precisions of peak heights and areas ranging from 1.5 to 3.5% for a 50 μg L〈sup〉−1〈/sup〉 standard solution. Good agreement between the determined and certified values of mercury species in a certified reference material of caprine blood (SRM 955c) together with good recoveries (93–101%) validated the accuracy of the method.〈/p〉〈/div〉

Description: 〈p〉Publication date: 2 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1574〈/p〉 〈p〉Author(s): Xiaohui Yan, Yingying Zhan, Dongdong Zhong, Yanshuo Li, Dapeng Wu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In order to achieve ultrafast solid phase micro-extraction (SPME) of trace organics in water samples, the robust polyimide/polyvinylpyrrolidone (PI/PVP) composite nanofiber was prepared by electrospinning. Unlike the nonwoven electrospun membrane bulk widely used for SPME, the hydrophilic PI/PVP nanofibers here can be easily dispersed into and recovered from water sample like a cloud, so nanofiber cloud SPME (NC-SPME) was proposed in this work. The extraction performance of the NC-SPME method was evaluated using phthalates and organochlorine pesticides as model analytes. The extracted analytes were then desorbed by acetone and eventually quantified by gas chromatography-mass spectrometry (GC–MS). The extraction equilibrium was reached in 30 s for most of the phthalates and 2 min for organochlorine pesticides. While for bar-SPME, the equilibrium time was much longer than 2 h. At the extraction time of 5 min, the recoveries of phthalates and organochlorine pesticides were more than 34% and 52% by the NC-SPME method while they were less than 15% and 10% respectively by the bar-SPME method. In a word, the NC-SPME method presented significant advantages such as fast equilibrium and high recoveries compared to bar-SPME. For the phthalates analysis of real samples by NC-SPME, 5 mL of water sample was used for a 5-min extraction, linear range covered 1–2 orders of magnitude with correlation coefficients (r) higher than 0.99 and limits of detection (LODs) at ng/L levels for all of the tested water samples. This method will be useful for the rapid micro-extraction of other kinds of organics in water samples even biological fluid samples due to the stable composition, ultra-hydrophilic surface of PI/PVP nanofiber, and the biocompatible nature of PVP.〈/p〉〈/div〉

Description: 〈p〉Publication date: 2 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1574〈/p〉 〈p〉Author(s): A. Auer, R. Kapeller, K. Rothberger, M. Schütte〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A gas chromatographic method for the determination of volatile contaminants (halogenated solvents, benzene, toluene, ethyl-benzene, xylenes, styrene) and phenol in e-liquids was developed and validated with a working range of 0.01 (limit of quantification) to 0.5 mg/l, and variation coefficients between 2 and 14%. Selectivity performing MS/MS-detection was sufficient for all analytes except for phenol: e-liquids contain high amounts of aroma compounds in excess of 10〈sup〉5〈/sup〉 compared to phenol. A number of these compounds potentially interfere at the retention time of phenol, showing all masses (including daughter ions and transitions) of phenol. To allow the detection of phenol in this matrix, a novel approach of adding a polar molecule to the injection solvent was used, modulating the polarity of the column, and thus the retention time of phenol. By adding 3 μl/ml and 10 μl/ml of 1,2-propanediol the retention time of phenol was shifted by 0.06 and 0.11 min respectively, while interfering peaks have not been shifted. This allowed a reliable confirmation of the presence of phenol. The introduced approach is an easy way to generate an additional chromatographic dimension for confirmation purposes, not requiring additional equipment.〈/p〉〈/div〉

Description: 〈p〉Publication date: 2 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1574〈/p〉 〈p〉Author(s): Walter B. Wilson, Lane C. Sander〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The research presented here describes the development of two analytical methods for use in the certification of a ginsenoside calibration solution Standard Reference Material (SRM) 3389 consisting of seven ginsenosides: Rg1, Re, Rf, Rb1, Rc, Rb2, and Rd. The new methods utilized the liquid chromatographic (LC) separation of ginsenoside mixtures with absorbance detection (UV) and mass spectrometry (MS). Ginsenosides Rb3, Rg2, Rg3, Rh1, and Rh2 were evaluated for use as internal standards for LC/MS measurements. The 12 ginsenosides were baseline resolved by gradient elution LC/UV, with an initial mobile phase composition of 22% acetonitrile and 78% water, flow rate of 0.7 mL/min, and column temperature of 25 °C. The work presented here includes a detailed investigation into the optimization of the chromatographic conditions to minimize measurement biases that result from unresolved constituents. Temperature and mobile phase composition are known to play a significant role in column selectivity; however, flow rate is expected to influence primarily the separation efficiency and detection sensitivity. In the current study, column selectivity changed with changes in flow rate and the relative retention of ginsenoside Rg2 and Rh1 changed as the flow rate increased from 0.6 mL/min to 1.0 mL/min.〈/p〉〈/div〉

Description: 〈p〉Publication date: 16 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1576〈/p〉 〈p〉Author(s): Maryam Rajabi, Nooshin Ghassab, Maryam Hemmati, Alireza Asghari〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, a new extraction medium based on a quite bio-compatible and bio-degradable deep eutectic solvent comprising choline chloride and phenylethanol (ChCl: Ph-ETOH) was simply and cheaply synthesized at room temperature. At the next step, it was effectively utilized at the service of air agitated-emulsification microextraction (AA-EME) of two major amphetamine-type stimulants (ATSs) in human plasma and pharmaceutical wastewater pursued by high performance liquid chromatography-ultraviolet detection (HPLC-UV). This safe, effective, and rapid enrichment process based on the new low-density DES was easily practicable via a homemade extraction cell possessing a narrow neck and with no extra demand the emulsifier intermediates. Statistical study of main parameters effects using central composite design (CCD) combined with desirability function (DF) demonstrated that pH 12, 250 μL of extraction solvent, 8 air agitation cycles, and 5% of salt amount resulted in maximum extraction efficiencies (63–66%) with DF value close to 0.98. Under optimal conditions, wide linear dynamic ranges (LDRs) of 15.0–2000 and 8.0–3000 ng mL〈sup〉−1〈/sup〉 with the determination coefficients (R〈sup〉2〈/sup〉s) close to 0.99 were obtainable for amphetamine and methamphetamine, respectively. Low limits of detection (LODs) as well as relative standard deviations (%RSDs, n = 3) were found to be 2.0–5.0 ng mL〈sup〉−1〈/sup〉 and 5.7–7.8%, respectively. Also, enrichment factors (EFs) were quantitative in the span of 47–50. On the other hand, satisfactory and accurate assessment at low levels close to therapeutic and toxic domains in human plasma sample and pharmaceutical wastewater was successfully obtained.〈/p〉〈/div〉

Description: 〈p〉Publication date: 2 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1574〈/p〉 〈p〉Author(s): Garrett Hellinghausen, M. Farooq Wahab, Daniel W. Armstrong〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In some cases, trace component analysis only requires a sensitive and high-resolution mass spectrometer. However, enantiomers must be completely separated to be differentiated with a mass spectrometer, which is highly dependent on the stationary-mobile phase composition. In case of a challenging chiral separation, instead of trying new columns for screening purpose, resolution enhancement techniques could be used to resolve partially overlapping peaks. A well-known enhancement method is the power law, which increases the linear dynamic range of each analyte and reduces excessive noise. In many cases, the peak noise can decrease significantly by applying the power law. However, the main drawback is that this approach changes relative peak areas and heights of each peak in a non-linear fashion which limits its use for quantitative purposes. In this study, a normalized power law was utilized for extracting correct area information. It is a simple (5 step) protocol that only requires Microsoft Excel, and results in enhanced visualization of trace components, especially in low signal/noise environments, and makes integration convenient and reproducible. Several difficult chiral trace component analyses were investigated, including applications pertaining to ultrafast high-throughput chromatography, enantiopurity, and peak purity analysis. For complicated cases with multiple overlapped peaks of different resolutions, a segmented normalized power law was utilized. A trace component coeluting near a dead volume peak and a trace enantiomeric component in the tail of the corresponding enantiomeric peak were virtually enhanced. As an additional tool, first and second derivatives were utilized to identify if an enantiomeric impurity is coeluting with the dominant enantiomer under overload conditions. Idiosyncrasies of the derivative test are discussed. This study shows how these simple approaches can be used for accurate quantitation, specifically for trace enantiomeric components.〈/p〉〈/div〉

Description: 〈p〉Publication date: 23 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1577〈/p〉 〈p〉Author(s): Dimitri Fichou, Imanuel Yüce, Gertrud E. Morlock〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Optimization of the ionization parameters in mass spectrometry does not guarantee a sufficient response and successful signal assignment when analyzing unknown compounds presenting signals of low intensity. The interpretation is difficult as the mass signals of degradation products are often less intense than background signals. Important information may be overlooked. Such critical and time consuming data analysis was overcome by developing a new strategy and open-source software called eicCluster offering unsupervised machine learning algorithms and powerful interactive visualization tools that made data processing fast and intuitive. Using eicCluster for high-performance thin-layer chromatography coupled with high-resolution mass spectrometry, mass signals of degradation products were highlighted in a stressed formulation, which were hardly found until linked to the new software. Owed to (1) preprocessing leading to intensity-agnostic signals and (2) the t-SNE algorithm, clustering mass signals based on their similarity, even compound ions present at low intensities were separated in subclusters from background signals (〈em〉in silico〈/em〉 highlighting). The resulting 2D maps allowed a new view on the data set to target molecules (degradation products) in complex mixtures. In addition to this new source of information, targeted on-surface synthesis of degradation products (〈em〉in situ〈/em〉 highlighting) was shown to support a fast structure elucidation when standards are not commercially available. It allowed a better understanding of the proposed degradation reactions in the formulation. As proof of principle, an original example formulation, its stressed samples as well as the proposed degradation products of on-surface synthesis were compared. 〈em〉In silico〈/em〉 and 〈em〉in situ〈/em〉 signal highlighting substantially eased data processing in structure elucidation.〈/p〉〈/div〉

Description: 〈p〉Publication date: 26 October 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1573〈/p〉 〈p〉Author(s): H. Daniel Bahaghighat, Chris E. Freye, Derrick V. Gough, Paige E. Sudol, Robert E. Synovec〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Ultrafast modulation with a modulation period 〈em〉P〈/em〉〈sub〉M〈/sub〉 ≥ 50 ms via a pulse flow valve is demonstrated for comprehensive two-dimensional gas chromatography (GC × GC) and comprehensive three-dimensional (3D) gas chromatography (GC〈sup〉3〈/sup〉). Significant increases in peak capacity and peak capacity production are achieved for GC × GC and GC〈sup〉3〈/sup〉 relative to previous studies due to using pulse flow valve modulation. Due to the nature of the “partial” modulation process, the separation dimension following pulse flow valve modulation is not a traditional chromatogram, rather requires data processing to convert the data to expose the encoded chromatographic information, producing “apparent” chromatographic peaks. In the GC × GC mode, a 115-component test mixture was evaluated using a 〈em〉P〈/em〉〈sub〉M〈/sub〉 of 500 ms, creating an apparent 〈sup〉2〈/sup〉D peak width-at-base 〈sup〉2〈/sup〉〈em〉W〈/em〉 with an average of 25 ms, producing a 〈sup〉2〈/sup〉〈em〉n〈/em〉〈sub〉c〈/sub〉 of 20. Based on the average 〈sup〉1〈/sup〉〈em〉W〈/em〉 of 1.0 s for the 6 min first dimension 〈sup〉1〈/sup〉D separation, an ideal peak capacity 〈em〉n〈/em〉〈sub〉c,2D〈/sub〉 of 7200 is achieved (1,200/min peak production). For a high-speed GC × GC separation (30 s run), a 〈em〉P〈/em〉〈sub〉M〈/sub〉 of 75 ms produced apparent 〈sup〉2〈/sup〉〈em〉W〈/em〉 of 8 ms, ideal for the third dimension of a GC〈sup〉3〈/sup〉 instrument. Using the knowledge gained from this high-speed GC × GC experiment, the pulse flow valve was implemented as the second modulator in GC〈sup〉3〈/sup〉. Three samples were evaluated in the GC〈sup〉3〈/sup〉 mode: a simple mixture containing 18 compounds (to illustrate basic concepts), the 115-component test mixture (to determine peak capacity figures-of-merit), and a diesel spiked with 8 polar compounds (to illustrate chemical selectivity benefits of GC〈sup〉3〈/sup〉). For the 115-component test mixture with a 〈sup〉1〈/sup〉〈em〉P〈/em〉〈sub〉M〈/sub〉 of 1.2 s and a 〈sup〉2〈/sup〉〈em〉P〈/em〉〈sub〉M〈/sub〉 of 60 ms, average 〈sup〉1〈/sup〉〈em〉W〈/em〉 of 3.2 s, 〈sup〉2〈/sup〉〈em〉W〈/em〉 of 130 ms, and apparent 〈sup〉3〈/sup〉〈em〉W〈/em〉 of 13 ms were produced, resulting in a 〈sup〉1〈/sup〉〈em〉n〈/em〉〈sub〉c〈/sub〉 of 210, 〈sup〉2〈/sup〉〈em〉n〈/em〉〈sub〉c〈/sub〉 of 9.2, and 〈sup〉3〈/sup〉〈em〉n〈/em〉〈sub〉c〈/sub〉 of 5, respectively. Hence, an ideal peak capacity, 〈em〉n〈/em〉〈sub〉c,3D〈/sub〉 of ∼10,000 for GC〈sup〉3〈/sup〉 was achieved for the 11 min 〈sup〉1〈/sup〉D separation window of the 115-component test mixture.〈/p〉〈/div〉

Description: 〈p〉Publication date: 16 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1576〈/p〉 〈p〉Author(s): Concepción Abril, Juan Luis Santos, José Luis Malvar, Julia Martín, Irene Aparicio, Esteban Alonso〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A method for the determination of 23 emerging concern pollutants in digested sludge, compost and soil has been developed. Target pollutants include six perfluorinated compounds (5 perfluorocarboxylic acids and perfluorooctanesulfonic acid), the plasticizer bisphenol A, four anionic surfactants (sodium alkylsulfates), four preservatives (parabens), two antimicrobial agents (triclosan and triclocarban) and six UV-filters (benzophenones). Sample treatment was based on ultrasound-assisted extraction with 3 mL of methanol:acetic acid (95:5, v/v) and clean-up by dispersive solid-phase extraction (d-SPE) with C18. Analytical determination was carried out by liquid chromatography-tandem mass spectrometry. Extraction solvent, sonication time, number of extraction cycles and type and amount of d-SPE sorbent were optimized. Due to the physical-chemical properties of target compounds, and the high number of sample treatment variables involved, a Box-Behnken design was applied to method optimization. The method was validated by means of spiked samples. Method detection limits were in the range from 0.01 to 6.2 ng g〈sup〉−1〈/sup〉 dry matter. Accuracy and precision were evaluated at three spike levels in each type of sample matrix. Accuracy, expressed as relative recovery, was in the range from 70% to 120% for most of the compounds and spike levels. Precision, expressed as relative standard deviation, was equal or below 21%. To the best of our knowledge, the proposed method constitute the first analytical method for multiclass determination of emerging pollutants in digested sludge, compost and soils.〈/p〉〈/div〉

Description: 〈p〉Publication date: 23 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1577〈/p〉 〈p〉Author(s): Avi Weissberg, Moran Madmon, Maor Elgarisi, Shai Dagan〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A highly sensitive method for the detection and identification of sarin (GB), soman (GD) and cyclosarin (GF) chemical warfare agents (CWAs) in environmental outdoor and indoor matrices such as soil, asphalt, linoleum, formica, concrete and cloth was developed. The method incorporates derivatization of the G-type nerve agent extracts with 2-[(dimethylamino)methyl]phenol (2-DMAMP), followed by LC-ESI(+)-MS/MS analysis. Four LC-amenable extraction solvents were explored in terms of their extraction efficiency and the reaction rate of the derivatizing agent. The reaction time, temperature and derivatization reagent amount were optimized. The optimal procedure was found to be extraction with water by agitation (2 min), followed by the addition of 2-DMAMP directly into the injection vial and stirring for 5 min prior to LC-ESI(+)-MS/MS analysis, without any other pretreatment. The method was applied to real-world samples and exhibited very low detection limits (LODs) of 0.8–20 pg/cm〈sup〉2〈/sup〉 in asphalt, linoleum, cloth, formica and concrete and 4 pg/g in soil. The newly developed method demonstrated significantly superior sensitivity compared to conventional GC–MS- and LC–MS-based methods for the identification of G-nerve agents and allowed the determination of both G-nerve agents and their hydrolysis products within a single LC–MS/MS run. The proposed methodology may be practical for verifying contaminated matrices collected in the battlefield or terror scenes in forensic investigations where trace level analysis is required.〈/p〉〈/div〉

Description: 〈p〉Publication date: 16 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1576〈/p〉 〈p〉Author(s): Jing Xie, Jing Xiong, Li-Sheng Ding, Li Chen, Hua Zhou, Liang Liu, Zhi-Feng Zhang, Xue-Mei Hu, Pei Luo, Lin-Sen Qing〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Although herb medicines have become the major source for new drug discovery, many of them are largely under-explored due to the purity-activity relationship. Efficient identification of bioactive compounds in conventional stepwise separation and isolation has not yet been elucidated. Therefore, we proposed a new separation strategy for holism understanding of herb pharmacology using molecularly imprinted polymers (MIPs). Astragali Radix (AR), important in traditional Chinese medicine, was chosen in this study for multicomponent knockout followed by bioactivity evaluation. We prepared calycosin molecularly imprinted polymers (calycosin-MIPs) which could selectively recognize flavonoid aglycons in AR. The molecular selectivity of calycosin-MIPs as a critical parameter was evaluated using the template and other high content compounds in AR. Based on it, using the calycosin-MIPs material via solid-phase extraction procedures was applied for the knockout of flavonoid aglycons in AR. Finally, hypoxia/reoxygenation model in H9c2 cells was used to evaluate the activity of the AR extract before and after knockout. The results showed that calycosin-MIPs as recognition materials for flavonoid aglycons in AR are applied in one-step separation with high selectivity and tunability. The subextract in the absence of flavonoid aglycons has been demonstrated to clarify the cardio-protective components of AR. In conclusion, this proof-of-principle study is the first one showing that molecular imprinting technology coupled with a bioassay can be used to explore the bioactive variability from the perspective of multicomponent separation of herbal medicine.〈/p〉〈/div〉

Description: 〈p〉Publication date: 30 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1578〈/p〉 〈p〉Author(s): Yanni Lv, Jia Fu, Qianqian Jia, Delu Che, Yuanyuan Lin, Shengli Han, Langchong He〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉β-Hexosaminidase is one of the enzymes that is secreted from mast cells via antigen-induced degranulation and has frequently been used as an indicator of anaphylactic reactions. The main method for determining β-hexosaminidase is indirect, “substrate-based” and shows limitations. Hence, development of an accurate detecting method is particularly important and urgently needed. In this study we developed a liquid chromatography tandem mass spectrometry (LC–MS/MS) method for measuring β-hexosaminidase. Laboratory of allergic diseases 2 (LAD2) cells were stimulated with compound 48/80 (C48/80), the supernatant was collected and subjected to in-solution protein digestion; the obtained peptides were desalted, concentrated, separated and analyzed with an LC-tandem MS instrument. A peptide with the sequence “LAPGTIVEVWK” was selected for quantitative analysis, and four other peptides for qualitative research. The time-effect relationship curve was studied, and the results of the LC–MS/MS method were found to be almost consistent with those obtained via the conventional method. The method was then employed to measure β-hexosaminidase released from LAD2 cells stimulated with potential allergens, and the results showed that it can be applied to determine the potential allergenicity of drugs. This new method showed good specificity, high sensitivity and a wide application range. It could be used to evaluate allergic reactions, providing a guide for medication safety during clinical testing.〈/p〉〈/div〉

Description: 〈p〉Publication date: 16 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1576〈/p〉 〈p〉Author(s): Andrey Samokhin〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In the field of gas chromatography–mass spectrometry, linear quadrupole instruments remain the most popular. Quadrupole mass spectrometers are scanning instruments. It means that ions with different 〈em〉m/z〈/em〉 values pass through the quadrupole sequentially. When analyte concentration changes during scan period, recorded mass spectrum is distorted. This phenomenon is called spectral skewing. There are two misconceptions associated with the spectral skewing: (1) the spectral skewing can affect the results of library search; (2) bilinear chemometric methods are often applied to skewed (distorted) GC/MS data to perform automatic data processing. We attempt to clarify these misconceptions. We can conclude that even strong distortion of mass spectrum (caused by the spectral skewing) practically does not change efficiency of automatic search against mass spectral database. On the other hand, even minor distortion of data (caused by the spectral skewing) can significantly distort results of automatic data processing (especially in the case of minor components). Interactive Excel files (presented in Supplementary material) illustrate our findings.〈/p〉〈/div〉

Description: 〈p〉Publication date: 9 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1575〈/p〉 〈p〉Author(s): David Thornton, Linda Barton, Leo Hsu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We developed an automated countercurrent chromatography (CCC) process to isolate anthocyanins from black currant extract utilizing a solvent system of methyl-t-butyl ether, n-butanol, acetonitrile and water with pH adjusted by addition of trifluoroacetic acid in normal phase mode. The process has excellent repeatability as indicated by the high purity of isolated products (90% or better) and the low retention time variability (〈10% RSD overall and 〈5% RSD at constant mass loading). In addition, we determined solvent system ratios to facilitate independent preparation of stationary and mobile phases which enabled us to reduce solvent waste by 70%.〈/p〉〈/div〉

Description: 〈p〉Publication date: 30 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1578〈/p〉 〈p〉Author(s): C. Gardana, P. Simonetti〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉〈em〉Stevia rebaudiana〈/em〉 extracts are used as sweeteners in several countries worldwide. Several extracts of diverse composition are available on the market, and their taste depends on the contents of the various steviol glycosides. This study presents an accurate method for the qualitative and quantitative determination of steviol glycosides in 40 〈em〉Stevia〈/em〉 extracts, 7 sweeteners and 3 〈em〉Stevia〈/em〉-sweetened beverages by a UHPLC coupled to an Orbitrap mass spectrometer. The sub-2 μm amide column provided the separation of all the target analytes in a run time of 30 min with high resolution. The effect of different eluent compositions on the ionisation efficiency of the steviol glycosides was studied. The optimal ionisation conditions were achieved in negative mode using 0.05% formic acid. Under this condition, adducts were not found, [M-H]〈sup〉−〈/sup〉 were the main ions and the spontaneous loss of a glucose residue at C19 was reduced. The %RSD for intra- and inter-day precision for all eleven analytes varied from 2.1 to 4.2% and 3.0–5.1%, respectively. The recoveries from spiked 〈em〉Stevia〈/em〉 extract samples were greater than 95% for all analytes. Rebaudioside A was the most abundant, ranging from 23 to 102%. Nine 〈em〉Stevia〈/em〉 extracts and one drink were not compliant with the European Regulation. Isosteviol was under the LOD in all samples and steviol was found in four samples in quantities in the range 0.01–0.03%.〈/p〉〈/div〉

Description: 〈p〉Publication date: 16 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1576〈/p〉 〈p〉Author(s): Chi Zhang, Xiuqin Li, Yanling Chen, Chao Wei, Xiaomin Li, Qinghe Zhang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Compound-independent calibration (CIC) is a quantitative method that can quantify other compounds using a structure-independent compound as the calibrant. In this study, the potential and application of CIC method for the determination of polybrominated diphenyl ethers (PBDEs) using GC-ICP-MS was investigated. The effects of sample introduction conditions, the flow rate of the carrier gas, splitless delay time and the matrix of the complex sample on the response of 11 PBDEs compounds were explored. When pulsed splitless injection was used, the transmission efficiency of analytes from the inlet to the column can speed up with increasing injection temperature and pulse pressure, the elemental response of bromine of each analyte becomes closer. Under optimized chromatographic conditions, the response is independent of the compound can be found from the slope of the pure solution standard from tri- to hepta- brominated compounds (BDE 28 as reference) ranged from 0.968 to 1.001 (R〈sup〉2〈/sup〉〉0.998).〈/p〉 〈p〉The degradation ratio of BDE 209 in the GC-ICP/MS system was estimated by the CIC method to be 18.7%. During the determination of fish tissue sample, big difference of the elemental response ratio (BDE 28 as reference) was obtained range from 0.678 to 0.976. However, a similar elemental response was observed among isomers range from 0.990 to 1.056. This may mean that the isomers can be calibrated to each other in a complex matrix sample. The CIC method was validated by determination 3 PBDEs in NIST SRM 1947 frozen fish tissue certified reference materials using isomers as reference compounds. The recoveries of BDE 49 and BDE 66 were 105.7% and 88.1% by using BDE 47 as calibrants, and that of BDE 155 was 108.8% by using BDE 154 as calibrant.〈/p〉 〈/div〉

Description: 〈p〉Publication date: 16 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1576〈/p〉 〈p〉Author(s): Omar H. Ismail, Michela Antonelli, Alessia Ciogli, Michela De Martino, Martina Catani, Claudio Villani, Alberto Cavazzini, Michael Ye, David S. Bell, Francesco Gasparrini〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this work the simultaneous separation of chiral active pharmaceutical ingredients (API) in salt form from their counterions has been performed by using different high-efficiency macrocyclic glycopeptide-based chiral stationary phases (CSPs). Not only a new zwitterionic vancomycin-based CSP has been prepared (similarly to what was done for teicoplanin) but macrocyclic selectors have also been bonded to sub-2 μm fully porous silica particles through traditional ureidic linkage to obtain versions of CSPs suitable for ultra-high performance applications. The direct separation of chiral APIs and counterions is particularly attracting since it simplifies the workflow traditionally used with reduction of analysis time and costs. The wide selection of macrocyclic antibiotics CSPs now available has allowed to manage different cases that can happen in the simultaneous separation of APIs and their counterions (either cations or anions). Indeed, while inorganic cations are retained on traditional vancomycin- and teicoplanin-based CSPs, inorganic anions are almost unretained (due to Donnan’s effect). On the other hand, cations and anions can be both retained on the zwitterionic versions of these CSPs. Afterwards, zwitterionic CSPs allowed the separation of other compounds including N-derivative amino-acids, profens, polyols, sugar anomers, oligosaccharides and inorganic anions/cations opening new perspectives in the use of this family of CSPs.〈/p〉〈/div〉

Description: 〈p〉Publication date: 16 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1576〈/p〉 〈p〉Author(s): Young Beom Kim, Joon Seon Yang, Myeong Hee Moon〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Steric transition in flow field-flow fractionation (FlFFF) was investigated under field programming by varying the channel thickness of a frit inlet asymmetrical FlFFF (FI-AF4). Steric transition is a typical inversion in sample elution mode from the increasing order of diameter (normal mode) to the opposite order (steric mode). Owing to the co-elution of two different-sized particles in the steric transition region where particles elute by the combination of the two elution modes, a loss of information in determining the accurate size of sample components in field-flow fractionation occurs. In this study, the effect of field programming on the steric transition in FI-AF4 was examined with the increase in channel thickness in order to increase the diffusional contribution of particle retention with the simultaneous reduction of steric contribution. This study demonstrated that the steric inversion diameter can be increased to 〉1 μm by programming the crossflow rate and by increasing the channel thickness to 350 and 490 μm. The present study also investigated the effects of outflow rate and initial field strength on the particle separation in field-programmed FI-AF4.〈/p〉〈/div〉

Description: 〈p〉Publication date: 16 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1576〈/p〉 〈p〉Author(s): Wenqing Li, Rong Wang, Zilin Chen〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A novel metal-organic framework UiO-66-modified cotton was prepared and applied to solid phase microextraction of non-steroidal anti-inflammatory drugs, namely ketoprofen, naproxen and flurbiprofen. UiO-66 was immobilized onto the surface of cotton by a polydopamine functionalized method. The resultant cotton@PDA@UiO-66 was characterized by Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy. The solid phase microextraction conditions were optimized, including sampling flow rate, formic acid content of the eluent, pH value of sample solution, NaCl content and sample volume. By combining with HPLC, this method showed high extraction efficiency (the enrichment factors of ketoprofen, naproxen and flurbiprofen were 44, 49 and 45, respectively), wide linear range (0.1–500 ng/mL), good linearity with R ≥ 0.9996 and satisfactory sensitivity (LODs ≤ 0.03 ng/mL, LOQs ≤ 0.1 ng/mL), as well as good reproducibility (RSD ≤ 4.51%). This method was also successfully applied to extraction of NSAIDs in swine muscle sample. Good recoveries were obtained, ranging from 88.54% to 95.7% with relative standard deviations less than 3.77%.〈/p〉〈/div〉

Description: 〈p〉Publication date: 2 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1574〈/p〉 〈p〉Author(s): Tahereh Golzari Aqda, Shima Behkami, Habib Bagheri〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, cellulose acetate (CA) fibers were prepared using different solvent systems in electrospinning. The recorded scanning electron microscopy micrographs indicated that the morphology of the prepared fibers is closely associated with the type of electrospinning solvents. The prepared CA fibers were used as an extractive phase for on–line micro–solid phase extraction (μ-SPE) of nonsteroidal–inflammatory drugs (NSAIDs) in biological samples pursued by HPLC–UV determination. Work conducted on this research ascertained that the use of dichloromethane:acetone (3:1, v/v) solvent system in the CA dissolution for electrospinning, leads to the formation of porous ribbon–like fibers and subsequent excellent extraction efficiencies for the selected drugs. Moreover, the effects of diverse parameters on the extraction efficiency were surveyed and optimized. The proposed method was used for determination of naproxen, diclofenac and mefenamic acid in human urine and plasma samples. The optimized method was validated and the limits of detection (1.0–2.4 μg L〈sup〉−1〈/sup〉), limits of quantification (3.3–8.0 μg L〈sup〉−1〈/sup〉) and linear dynamic range (4.0–1000.0 μg L〈sup〉−1〈/sup〉) were obtained. The reproducibility (relative standard deviation: 2.6–7.9%) was in an acceptable range. Trueness of the procedure was accomplished through recovery assays in urine (94–105%) and plasma (85–102%) samples, indicating the minor contribution from the sample matrix. Finally, the CA porous fibers within the framework of the μ-SPE method were found to be appropriate for the separation and determination of the selected drugs in urine and plasma samples collected from treated patients. Also, the adsorption behavior of the porous fibers was well described by Freundlich isotherm and porous fibers showed acceptable adsorption capacity.〈/p〉〈/div〉

Description: 〈p〉Publication date: 23 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1577〈/p〉 〈p〉Author(s): Liwei Cao, Qiuxia Liang, Tian Wei, Yihui Shi, Tao Deng, Jianxin Meng〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This study combines a high-performance liquid chromatography-fluorescent detection method (HPLC-FLD) with in-situ cell imaging for the sensitive analysis of glutathione (GSH), cysteine (Cys) and homocysteine (Hcys), using BODIPY®507/545 IA as a labeling reagent. The analytical potential of BODIPY®507/545 IA in cell imaging was deeply explored, concerning fluorescent response, selectivity, cell-permeability, biotoxicity and so on. It is demonstrated that BODIPY®507/545 IA has good biocompatibility and the fluorescence intensity is enhanced remarkably after reacting with thiols. The best derivative condition was obtained in boric acid buffer (0.05 mmol/L, pH 9.5) at 45 °C for 15 min. For chromatographic method, two sensitive methods, HPLC-FLD and capillary electrophoresis-laser-induced fluorescence detection (CE-LIF) were both developed, validated, and compared. The detection limits for the thiols ranged from 5 to 10 nmol/L with HPLC-FLD and 0.5 nmol/L for the CE-LIF method. Finally, HPLC-FLD is adopted to quantify the thiols in HepG2 cell samples after cell imaging.〈/p〉〈/div〉

Description: 〈p〉Publication date: 2 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1574〈/p〉 〈p〉Author(s): Mohammad Saraji, Hoda Ghambari〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉For the first time, the possibility of the use of liquid anion exchangers in dispersive liquid–liquid microextraction for the direct extraction of some inorganic anions (nitrite, nitrate, and iodide) was evaluated. In this technique, chloroform containing a liquid anion exchanger (trioctylamine) was used as extractant. The mixture of the extractant and disperser solvent (acetonitrile) was injected into the acidic sample solution. The protonated trioctylamine formed a water-insoluble salt with the inorganic anions (analytes). After the phase separation and stripping of the analytes from the extractant, the analytes were determined by liquid chromatography with UV detection. Various parameters affecting the extraction efficiency were investigated. Under the optimum conditions, broad linear dynamic ranges, with determination coefficients (〈em〉r〈sup〉2〈/sup〉〈/em〉) higher than 0.998, and enrichment factors between 94 and 244 were obtained. The limits of detection and quantification were in the range of 0.1–0.5 and 0.4–1.7 μg L〈sup〉−1〈/sup〉, respectively. Also, the values of intra- and inter-day relative standard deviations were 3.5–5.8% and 5.5–7.8%, respectively. Various real water samples including sea, tap, river, spring and mineral water were analyzed by the method. The method was sensitive, simple, inexpensive and capable of the simultaneous extraction and determination of the selected inorganic anions.〈/p〉〈/div〉

Description: 〈p〉Publication date: 26 October 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1573〈/p〉 〈p〉Author(s): Sandrine Huclier-Markai, Alicia Grivaud-Le Du, Estelle N’tsiba, Gilles Montavon, Marie Mougin-Degraef, Jacques Barbet〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Alpha-particle-emitting radionuclides have been the subject of considerable investigation as cancer therapeutics, since they have the advantages of high potency and specificity. Among α-emitting radionuclides that are medically relevant and currently available, the lead-212/bismuth-212 radionuclide pair could constitute an 〈em〉in vivo〈/em〉 generator. Considering its short half-life (T〈sub〉1/2〈/sub〉 = 60.6 min), 〈sup〉212〈/sup〉Bi can only be delivered using labelled carrier molecules that would rapidly accumulate in the target tumor. To expand the range of applications, an interesting method is to use its longer half-life parent 〈sup〉212〈/sup〉Pb (T〈sub〉1/2〈/sub〉 = 10.6 h) that decays to 〈sup〉212〈/sup〉Bi. The challenge consists in keeping 〈sup〉212〈/sup〉Bi bound to the vector after the 〈sup〉212〈/sup〉Pb decay. Preclinical and clinical studies have shown that a variety of vectors may be used to target alpha-emitting radionuclides to cancer cells. Nanoparticles, notably liposomes, allow combined targeting options, achieving high specific activities, easier combination of imaging and therapy and development of multimodality therapeutic agents (e.g., radionuclide therapy plus chemotherapy). The aim of this work consists in assessing the 〈em〉in vitro〈/em〉 stability of 〈sup〉212〈/sup〉Pb/〈sup〉212〈/sup〉Bi encapsulation in the liposomes. Indeed, the release of the radionuclide from the carrier molecules might causes toxicity to normal tissues. To reach this goal, Asymmetrical Flow Field-Flow Fractionation (AF4) coupled with a Multi-Angle Light Scattering detector (MALS) was used and coupling with a gamma (γ) ray detector was developed. AF4-MALS-γ was shown to be a powerful tool for monitoring the liposome size together with the incorporation of the high energy alpha emitter. This was successfully extended to assess the stability of 〈sup〉212〈/sup〉Bi-radiolabelled liposomes in serum showing that more than 85% of 〈sup〉212〈/sup〉Pb/〈sup〉212〈/sup〉Bi is retained after 24 h of incubation at 37 °C.〈/p〉〈/div〉

Description: 〈p〉Publication date: 16 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1576〈/p〉 〈p〉Author(s): Wolfgang Wach, Christoph Buttersack, Klaus Buchholz〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The chromatographic response of sugars at granulated zeolite pellets in preparative scale liquid chromatography is analyzed with respect to the distribution equilibrium and mass transfer. In contrast to hydrophilic FAU type zeolites their hydrophobic dealuminated counterpart, used here, can separate disaccharides the retention of which can strongly exceed those of the monosugars. The retention is correlated with data of batch adsorption studies from the literature. Whereas the retention decreases with increasing temperature, the peak sharpness shows the opposite trend. The effective mass resistance is calculated for a series of mono- and disaccharides. It increases with the capacity factor. The diffusion coefficient of the trehalulose disaccharide is restricted by a factor of about 2 in the macropores and by a factor of more than 10〈sup〉4〈/sup〉 in the micropores.〈/p〉〈/div〉

Description: 〈p〉Publication date: 26 October 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1573〈/p〉 〈p〉Author(s): Edward C.M. Chen, Edward S. Chen〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The use of the electron-capture detector, ECD, to measure molecular electron affinities and kinetic parameters for reactions of thermal electrons with molecules at atmospheric pressure separated by chromatography and the sensitive and selective quantitative analysis of certain classes molecules are reviewed. The evaluated ground state electron affinities of the main group elements and diatomic molecules from slightly positive, 0+, to 3.6 eV are summarized. The electron affinities of twenty-seven superoxide states determined from pulsed discharge ECD and other methods are used to calculate one dimensional potential energy curves in agreement with theory. Advances in literature searches have uncovered ECD data in dissertations and theses and in the Russian and Japanese literature. These data, unpublished radioactive and pulsed discharge ECD thermal data from the University of Houston laboratories are used to report and evaluate electron affinities. The accuracy and precision of ECD electron affinities of organic molecules are identified and tabulated so that they can be added to compilations. A procedure for calculating the temperature dependence of electron molecule reactions is presented using kinetic and thermodynamic data. These are used toselect the most appropriate equipment and conditions for ECD analyses and physical determinations.〈/p〉〈/div〉

Description: 〈p〉Publication date: 9 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1575〈/p〉 〈p〉Author(s): Sander Deridder, Wim Smits, Hamza Benkahla, Ken Broeckhoven, Gert Desmet〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We report on a numerical study of the thermal conductivity of core-shell particle packed bed columns. Covering a variety of packing structures and a broad range of mobile phase and porous zone conductivities, it was in all cases found that switching to particles with a highly conducting core (e.g., with a gold or copper core instead of a silica core) would produce a much smaller increase of the effective heat conductivity of the bed (k〈sub〉eff〈/sub〉) than previously expected in literature. We found maximal increases on the order of some 20–70%, which is much lower than the potential increases up to 2000% assumed in literature. The overestimation in literature could be attributed to the fact that this literature was based on an incorrect extrapolation of the Zarichnyak-model which was the heat conductivity model predominantly used up till now. On the other hand, the computed relationships between k〈sub〉eff〈/sub〉 and the core conductivity obtained in the present study are in good agreement with an analytical solution derived from the effective medium theory, a theory which is physically much more relevant for the case at hand than the Zarichnyak-model. The results also show that the observed increase in effective bed conductivity between fully porous and core-shell particle beds frequently observed in literature is not only due to the presence of the core, but that differences in the shell layer conductivity can play an equally important role. In addition, it could also be demonstrated that, if ways could be found to increase the conductivity of the shell layer, this would produce a much stronger increase of the overall bed conductivity than will ever be possible by increasing the conductivity of the cores.〈/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〉