ALBERT

Description: 〈p〉Publication date: Available online 28 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Shoji F. Nakayama, Tomohiko Isobe, Miyuki Iwai-Shimada, Yayoi Kobayashi, Yukiko Nishihama, Yu Taniguchi, Makiko Sekiyama, Takehiro Michikawa, Shin Yamazaki, Hiroshi Nitta, Masako Oda, Hiroshi Mitsubuchi, Masafumi Sanefuji, Shouichi Ohga, Nathan Mise, Akihiko Ikegami, Reiko Suga, Masayuki Shimono〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Poly- and perfluoroalkyl substances (PFAS) have been investigated in a number of cohort studies due to concern over their adverse health effects. The aim of this study was to develop a reliable, high throughput and cost-effective analytical method for a broad range of PFAS in human serum. Protein precipitation, automatic solid phase extraction (SPE) pre-treatment and column-switching LC-MS/MS were employed. The optimised and validated method was then used to analyse the levels of 28 PFAS in 339 maternal serum samples from Pilot Study of the Japan Environment and Children's Study. Perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluoroundecanoic acid (PFUnA) and perfluorooctane sulphonic acid (PFOS) were detected in all 339 samples at median (range) concentrations of 1.9 (0.46–15), 1.5 (0.32–10), 1.3 (0.25–4.5) and 3.7 (0.43–15) ng/ml, respectively. These levels are comparable to those reported in previous studies using samples collected from various parts of the world. With a few exceptions, the remainder of the PFAS examined had lower detection rates but were found at concentrations similar to those reported in previous studies. The sensitivity and throughput ability of the method developed here are sufficient for its application in a large-scale biomonitoring study.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 28 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Belén Callejón-Leblic, Gema Rodríguez-Moro, Ana Arias-Borrego, Antonio Pereira-Vega, José Luis Gómez-Ariza, Tamara García-Barrera〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉One of the most important causes of the high mortality rate and low life expentancy of lung cancer is the detection at advanced stages. Thus, there is an urgent need for early diagnosis and the search of new selective biomarkers. Selenium is an important constituent of selenoproteins and a powerful antioxidant able to protect against cancer. In this work, the absolute quantification of selenium in selenoproteins and the total content in selenometabolites has been performed for the first time in serum from lung cancer patients (LC) and healthy controls (HC). To this end, a method for the simultaneous speciation of selenoproteins using size exclusion chromatography (SEC) and affinity chromatography (AF) with detection by ICP-QQQ-MS, and quantification by isotopic dilution (IDA) (SEC-AF-HPLC-SUID-ICP-QQQ-MS) was developed to determine the selenium concentration in eGPx, SEPP1 and SeAlb, as well as total selenometabolites, to find alterations that may serve as biomarkers of this disease. In the same way, a method based on anion-exchange chromatography coupled to ICP-QQQ-MS was developed to quantify selenometabolites (SeCys2, SeMeSeCys, SeMet, selenite and selenate) in the same LC and HC serum samples. The results showed that the averaged concentrations of selenium in eGPx, SeAlb and selenite were significantly higher in LC patients (LC (eGPx: 21.24 ± 0.77 ng g〈sup〉−1〈/sup〉; SeAlb: 49.56 ± 3.16 ng g〈sup〉−1〈/sup〉 and Se(IV): 6.20 ± 1.22 ng g〈sup〉−1〈/sup〉) than in HC group (eGPx: 16.96 ± 0.53 ng g〈sup〉−1〈/sup〉; SeAlb: 38.33 ± 2.66 ng g〈sup〉−1〈/sup〉 and Se(IV): 3.56 ± 0.55 ng g〈sup〉−1〈/sup〉). In adittion, the ratios between selenoproteins and selenometabolits have been calculated for the first to study their potential use as LC biomarkers. The rates eGPx/SEPP1, SEPP1/SeAlb, eGPx/Se(IV) and SEPP1/Se(IV) were significantly different between LC and HC groups.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 28 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Li Zhou, Beibei Liu, Jin Guan, Zhen Jiang, Xingjie Guo〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Although various cyclodextrins (CDs) have been utilized to prepare organic polymer-based monolithic columns, there were few reports on fabrication of cyclodextrin functionalized hybrid monolithic columns. Herein, a sulfobutylether β-cyclodextrin (SBE-β-CD)-silica hybrid monolithic column was prepared by “one-step” method via the co-polymerization of hydrolyzed organosiloxane precursors and glycidyl methacrylate-sulfobutylether β-cyclodextrin (GMA-SBE-β-CD). The morphologies of prepared monolithic columns were observed by optical microscopy and scanning electron microscopy (SEM). The sulfobutylether β-cyclodextrin was incorporated into the polymeric structure, which was demonstrated by energy dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FTIR) spectrum and X-ray photoelectron spectroscopy (XPS). The resulting columns were used for chiral separations of twenty six racemic compounds, and satisfactory separation selectivity was obtained. Compared with other two kinds of neutral cyclodextrin (β-CD and HP-β-CD) based hybrid monoliths, sulfobutylether β-cyclodextrin-silica hybrid monolith showed superior chiral resolution. These results demonstrated the sulfobutylether β-cyclodextrin-silica hybrid monolithic column was promising in chiral compounds analysis.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 25 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Yongrui He, Meiling Qi〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This work presents a new triptycene-based stationary phase (TP-PEG) combining the three-dimensional (3D) triptycene (TP) framework with polyethylene glycol (PEG) moieties for gas chromatographic (GC) separations. Its statically coated capillary column showed high column efficiency of 5263 plates/m determined by naphthalene at 120 °C. Its Rohrschneider-McReynolds constants and Abraham solvation system constants were measured to characterize its polarity and molecular interactions with analytes of different types. As evidenced, the TP-PEG column showed high-resolution performance for the isomers of anilines, phenols, halobenzenes and alkanes with distinct advantages over the PEG columns, particularly those critical isomers such as 3,5-/2,3-xylidine (R = 2.94), 〈em〉m〈/em〉-/〈em〉p〈/em〉-chlorotoluene (R = 1.92), 〈em〉p〈/em〉-/〈em〉m〈/em〉-cresol (R = 1.89), 2,2-dimethylbutane/2-methylpentane (R = 1.51), 2,2,3-trimethylbutane /2,3-dimethyl pentane (R = 1.74) and 2,3-dimethylpentane/〈em〉n〈/em〉-heptane (R = 1.92). In addition, it exhibited good column repeatability and reproducibility with the relative standard deviation (RSD) values of 0.02%−0.09% for run-to-run, 0.13%−0.22% for day-to-day and 2.7%−4.1% for column-to-column, respectively, and a wide operational temperature range (30 °C−280 °C) . Its application to GC-MS analysis of the essential oil of 〈em〉Osmanthus fragrans〈/em〉 has proven its good potential for practical analysis of complex samples.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 27 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Kenneth D. Berthelette, Thomas H. Walter, Martin Gilar, Fabrice Gritti, Thomas S. MacDonald, Miguel Soares〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Hydrophilic Interaction Liquid Chromatography (HILIC) is a technique for retaining polar analytes that uses polar stationary phases and acetonitrile-rich mobile phases. While this technique has several advantages over reversed-phase liquid chromatography (RPLC), one main drawback is the reported need for longer column equilibration. The reason for this is not fully understood and is a topic of current investigation. In order to better understand and reduce the equilibration needs, accurate characterization of column equilibration under varying conditions is required. The current method of characterizing HILIC column equilibration produces limited data points per test, or low time resolution, and is highly dependent on the column and probe compounds being used. There is a need for an improved method for characterizing HILIC column equilibration, especially if trends across stationary phases are to be observed. In this work, MISER, or Multiple Injections in a Single Experimental Run, is evaluated as a possible tool for characterizing HILIC column equilibration. MISER improves time resolution by allowing for replicate injections without interruption of data collection, enabling a more thorough evaluation of column equilibration compared to traditional techniques. Experimental results gathered using MISER show that equilibration of a BEH Amide column is notably shorter when equilibrating from acetonitrile to mobile phases containing higher percentages of water. Column equilibration to a 10% aqueous mobile phase was found to be approximately 5-fold faster than equilibration to a 3% aqueous mobile phase.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 24 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Lei Cheng, Xin-an Yang, Meng-ting Shi, Wang-bing Zhang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Considering the huge difference of biological toxicity, it is extremely significant to recognize the exact content of arsenic species in actual samples. In this paper, a novel pretreatment technique for the efficient extraction of arsenic species from herbal samples is developed by dual-frequency ultrasound-assisted enzymatic digestion (DUED). The preservation of arsenic original form, reduction of the actual analysis time, environmental friendliness and free-interference in subsequent detection make this method over the traditional method such as wet digestion, ashing and some solvent extraction technologies. The combination of DUED and atomic fluorescence spectrometry realize the speciation analysis of arsenic in traditional Chinese medicine. The optimizations of experimental parameters have been achieved, and the potential mechanism is discussed. The experimental data showed that cellulase is suitable for the digestion of herbal matrix than α-amylase and papain. Ultrasound can significantly increase the rate of enzymatic hydrolysis of biological molecules, especially under dual-frequency ultrasound irradiation. The highest relative extraction efficiency can be obtained by combining 40 kHz ultrasonic bath (UB) with 20 kHz ultrasonic probe (UP). Two certified reference materials [CRMs, GBW(E)090066 and GBW(E)090067] and four practical herbs were used to evaluate the accuracy and practicability of the method. Inorganic arsenic, including trivalent arsenic and pentavalent arsenic, was the main species in the four herbal samples.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 23 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Akiyoshi Hirayama, Sho Tabata, Ryuhei Kudo, Masako Hasebe, Kumi Suzuki, Masaru Tomita, Tomoyoshi Soga〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Recently, ion chromatography coupled with mass spectrometry has been used for the determination of anionic metabolites. However, connection with a mass spectrometer in this method is not straightforward because backpressure produced by the addition of a make-up solution often affects the peak resolutions of the target metabolites. To overcome this problem, we developed a capillary ion chromatography-mass spectrometry method utilizing a double coaxial electrospray ionization sprayer. This method was not affected by backpressure and the number of theoretical plates was about three times that of a conventional sprayer. Under optimized conditions, 44 anionic metabolites, including organic acids, sugar phosphates, nucleotides, and cofactors, were successfully separated and selectively detected with a Q Exactive mass spectrometer. The calibration curves of the tested metabolites showed excellent linearity within the range of 1 to100,000 nmol/L and the correlation coefficient was greater than 0.991. The detection limits for these metabolites were between 1 and 500 nmol/L (0.4 and 200 fmol). The developed method was applied to the quantitation of anionic metabolites in cultured cancer cell samples with tumor necrosis factor (TNF)-α stimulation. This allowed for the successful determination of 105 metabolites. The levels of tricarboxylic acid cycle intermediates changed significantly after TNF-α stimulation. These results demonstrate that the developed method is a promising new tool for comprehensive analysis of anionic metabolites.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 23 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Xin-Mei Wang, Wen-Hua Ji, Li-Zong Chen, Jin-Ming Lin, Xia Wang, Ru-Song Zhao〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Disinfection by-products (DBPs) in drinking water can pose a health risk to humans. In this work, a new nitrogen-rich covalent organic frameworks (TpTt-COFs) was synthesized and applied firstly as a novel solid-phase extraction (SPE) trapping media for four ultra-trace levels of DBPs in drinking water samples. Under the optimal conditions, these DBPs were absorbed on a SPE cartridge; then, the DBPs were eluted with the optimized volume of eluent. The concentrated elution was detected and quantified by gas chromatography-mass spectrometry. Low limits of detection (0.0004∼0.0063 ng mL〈sup〉−1〈/sup〉), wide linearity (0.002∼50 µg L〈sup〉−1〈/sup〉), good reproducibility (1.54∼2.88%) and repeatability (1.30∼3.40%) were obtained. This novel method has been successfully applied to the analysis of ultra-trace levels DBPs in real drinking water samples. These accurate experimental results by this method indicated that the novel TpTt-COFs as a SPE trapping material was an attractive option for efficient and effective analysis of ultra-trace levels DBPs in future.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 23 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Yu Fan, Yan Zhang, Chao Peng, Xiao Chang, Lu Sun, Xiang-Jin Kong, Bao-Zhong Zhang, Lin-Yi Dong, Xian-Hua Wang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Traditional boron affinity materials usually capture cis-diol-containing molecules under alkaline condition, but some cis-diol-containing molecules, such as polyphenols, are unstable and easy to be oxidized and degraded under alkaline condition. Teamed boronate affinity (TBA) can specifically capture cis-diol-containing molecules under neutral condition. However, the report about combination of TBA and magnetic nanoparticle for the extraction was rare. Here, we fabricated two kinds of teamed boronate affinity magnetic nanoparticles (TBAMP), including Fe3O4@TBAP and Fe3O4@SiO2@TBAP. Adsorption capacities of cis-diol-containing molecules on the latter were similar to these on the former, but the latter possessed more superior regeneration performance than the former. Therefore, the TBAMP with more superior regeneration performance was used as magnetic solid-phase extraction (MSPE) adsorbent for capturing polyphenols under neutral condition. The TBAMP MSPE was optimized in detail, and combined with high-performance liquid chromatography-mass spectrometry (HPLC-MS) for the simultaneous determination of 13 kinds of polyphenols from Flos Lonicerae Beverage. The proposed method showed low limit of detection between 0.01 and 0.20 ng mL〈sup〉−1〈/sup〉. In blank Flos Lonicerae Beverage, 11 kinds of polyphenols ranged from 0.54 ng mL〈sup〉−1〈/sup〉 to 52.99 ng mL〈sup〉−1〈/sup〉 were detected. In the standard addition method, recoveries of cis-diol-containing polyphenols were between 85.7% and 102.1% with intra-day and inter-day relative standard deviation ranging from 3.2% to 5.1% and 5.3% to 7.3%, respectively.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 22 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Weiqiang Hao, Kai Wang, Bangyi Yue, Qiang Chen, Yibo Huang, Jianjun Yu, Dashuai Li〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉An expression for peak compression factor based on temporal peak widths is proposed which can be measured directly. The relationship between it and peak compression factor based on spatial peak widths is given. The experimental data presented in the Neue's work are reevaluated. The peak compression factor is recalculated by taking into account the curvature in the plot of logarithmic retention factor (ln〈em〉k〈/em〉) vs. mobile phase composition (〈em〉φ〈/em〉) and the variation in plate height (〈em〉H〈/em〉) with 〈em〉φ〈/em〉. The ln〈em〉k〈/em〉 vs. 〈em〉φ〈/em〉 plot is accounted for by quadratic solvent strength model (QSSM). The ln〈em〉H〈/em〉 vs. 〈em〉φ〈/em〉 plot is accounted for by QSSM and a quadratic equation that accounts for the plot of logarithmic peak width obtained under isocratic elution (ln〈em〉W〈sub〉I〈/sub〉〈/em〉) vs. 〈em〉φ〈/em〉. By taking these two factors into account, the discrepancy between experimental and predicted values of peak width is reduced. This result confirms the Neue's conclusion that the anomalous peak broadening reported previously may be an artifact of the procedure to determine the theoretical value of peak width. Moreover, by assuming linear gradient elution, constant column efficiency, and general solvent strength, the relationship between peak compression factors obtained under ideal and real situation respectively is discussed.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 22 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Baradwaj Gopal Ravi, Mary Grace E. Guardian, Rebecca Dickman, Zhen Q. Wang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Plants of the 〈em〉Digitalis〈/em〉 genus contain a cocktail of cardenolides commonly prescribed to treat heart failure. Cardenolides in 〈em〉Digitalis〈/em〉 extracts have been conventionally quantified by high-performance liquid chromatography yet the lack of structural information compounded with possible co-eluents renders this method insufficient for analyzing cardenolides in plants. The goal of this work is to structurally characterize cardiac glycosides in fresh-leaf extracts using liquid chromatography coupled with tandem mass spectrometry (LC/MS/MS) that provides measured accurate mass. Fragmentation of cardenolides is featured by sequential loss of sugar units while the steroid aglycone moieties undergo stepwise elimination of hydroxyl groups, which distinguishes different aglycones. Using a reverse-phase LC column, the sequence of elution follows diginatigenin→digoxigenin→gitoxigenin→gitaloxigenin→digitoxigenin for cardenolides with the same sugar units but different aglycones. A linear range of 0.8-500 ng ml〈sup〉−1〈/sup〉 has been achieved for digoxigenin, 〈em〉β〈/em〉-acetyldigoxin, and digitoxigenin with limits of detection ranging from 0.09 to 0.45 ng ml〈sup〉−1〈/sup〉. A total of seventeen cardenolides have been detected with lanatoside A, C, and E as major cardenolides in 〈em〉Digitalis lanata〈/em〉 while seven have been found in 〈em〉Digitalis purpurea〈/em〉 including purpurea glycoside A, B, and E. Surprisingly, glucodigifucoside in 〈em〉D. lanata〈/em〉 and verodoxin and digitoxigenin fucoside in 〈em〉D. purpurea〈/em〉 have also been found as major cardenolides. As the first MS/MS-based method developed for analyzing cardenolides in plant extracts, this method serves as a foundation for complete identification and accurate quantification of cardiac glycosides, a necessary step towards understanding the biosynthesis of cardenolide in plants.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 22 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Darien Yeung, Nicole Klaassen, Benilde Mizero, Victor Spicer, Oleg V. Krokhin〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Peptide retention time prediction models have been developed for zwitter-ionic ZIC-HILIC and ZIC-cHILIC stationary phases (pH 4.5 eluents) using proteomics-derived retention datasets of ~30 thousand tryptic peptides each. Overall, hydrophilicity of these stationary phases was found to be similar to the previously studied Amide HILIC phase, but lower compared to bare silicas. Peptide retention is driven by interactions of all charged (hydrophilic) residues at pH 4.5 (Asp, Glu, Arg, Lys, His), but shows specificity according to orientation of functional groups in zwitter-ionic pair. Thus, ZIC-cHILIC exhibits an increased contribution of negatively charged Asp and Glu due to the distal positioning of positively charged quaternary amines on the stationary phase. These findings confirm that HILIC interactions are driven by both peptide distribution between water layer adsorbed on the stationary phase and by interactions specific to functional groups of the packing material. Sequence-Specific Retention Calculator HILIC models were optimized for these columns showing 0.967–0.976 R〈sup〉2〈/sup〉-values between experimental and predicted retention values. ZIC-HILIC separations represent a good choice as a first dimension in 2D LC-MS of peptide mixtures with correlations between retention values of ZIC-HILIC against RPLC found at 0.197 (ZIC-HILIC) and 0.137 (ZIC-cHILIC) R〈sup〉2〈/sup〉-values, confirming a good orthogonality.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 25 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Ning Yuan, Jia Chen, Tianpei Cai, Zhan Li, Ming Guan, Liang Zhao, Hongdeng Qiu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A new stationary phase based on glucose-derived carbon dots-modified on silica (Sil-Glc-CDs) was prepared and applied in hydrophilic interaction chromatography (HILIC). The Sil-Glc-CDs column showed better retention ability and separation selectivity toward polar analytes, including amino acids, saccharides, ginsenosides, antibiotics, nucleosides, and nucleobases when compared with a commercial HILIC column and a home-made glucose-modified silica (Sil-Glc) column. The effect of the organic phase ratio, salt concentration, pH and column temperature on chromatographic retention behavior was investigated. In addition, the column exhibited good stability and column-to-column reproducibility (RSDs 0.80%-1.97%, n=3). Particularly, this column was successfully applied for the determination of the concentration of glucose (2.2 mg mL〈sup〉−1〈/sup〉) and fructose (3.4 mg mL〈sup〉−1〈/sup〉) in the goji berry solution.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 25 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Zhixu Chen, Qi Li, Taicheng Yang, Yaofeng Zhang, Minghong He, Huiyun Zeng, Xiaoman Mai, Yingtao Liu, Huajun Fan〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A simple, green and efficient method for extraction, purification and enrichment of pesticide residues of triazoles and pyrethroids in Longan fruit was developed by ultrasonic-assisted aqueous two-phase extraction (UAATPE) coupled to vortex-assisted dispersive liquid-liquid microextraction (VADLLME). Using an aqueous two-phase system (ATPS) of ethanol/K〈sub〉2〈/sub〉HPO〈sub〉4〈/sub〉 as extraction solvent, the composition of the ATPS, extraction temperature and time were investigated, respectively. Then VADLLME process also was optimized by investigating type and volume of extracting and dispersive solvents and vortex-assisted time and salt addition. The optimum conditions were as follows: the ATPS composition of ethanol concentration 30.0% (w/w) and K〈sub〉2〈/sub〉HPO〈sub〉4〈/sub〉 concentration 25% (w/w), extraction temperature 70°C and extraction time 15 min for UAATPE; 1-dodecanol 200 μL as extraction solvent, ethanol 1.25 mL as dispersive solvent, vortex-assisted time 1.5 min and addition of NaCl 4% (w/v) for VADLLME. Ethanol as extraction solvent and dispersive solvent could directly connect UAATPE with VADLLME without extra steps. By means of HPLC-DAD detection, nine pesticides including some isomers had good linearity ranged from 0.0200 to 13.59 μg/mL (R〈sup〉2〈/sup〉≥0.9957). LODs and LOQs were in the range of 0.005576−0.01740 μg/mL and 0.01859−0.05010 μg/mL, respectively. UAATPE-VADLLME coupled to HPLC was successfully applied to simultaneous determination of multiple pesticides in Longan fruit, and mean recoveries and RSDs were between 76.95% and 98.63%, 1.2% and 9.8%, respectively. Furthermore, myclobutanil, fenpropathrin and deltamethrin were detected in pericarp and pulp of Longan samples from different districts, respectively.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 25 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Marie Mézière, Ronan Cariou, Frédéric Larvor, Emmanuelle Bichon, Yann Guitton, Philippe Marchand, Gaud Dervilly, Bruno Le Bizec〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Chlorinated paraffins (CPs), or polychlorinated 〈em〉n〈/em〉-alkanes, form a complex family of chemicals as they exist as mixtures of several thousands of isomers. To facilitate their classification, they are subdivided into short-chains (C〈sub〉10〈/sub〉-C〈sub〉13〈/sub〉, SCCPs), medium-chains (C〈sub〉14〈/sub〉-C〈sub〉17〈/sub〉, MCCPs), and long-chains (C〈sub〉≥18〈/sub〉, LCCPs) and further subdivided according to their chlorination degree. Until recently, the most common strategy implemented for their analysis was GC-ECNI-LRMS, with the main disadvantage being the high dependence of the response to the chlorination degree and the incapability of analysing LCCPs. In this work, we developed a method based on liquid chromatography coupled with electrospray ionisation-Orbitrap mass spectrometry (LC-ESI-HRMS) to expand the analysis capabilities of CPs. Although the different physico-chemical properties of CPs have led to compromises on the choice of analytical parameters, the addition of a mixture of DCM/ACN post-column with appropriate LC-ESI(-)-HRMS parameters enabled optimal and simultaneous detection of SCCPs, MCCPs and LCCPs from 10 to 36 carbons in one single injection. The combination of both the optimised LC-ESI parameters and the high resolution of the mass spectrometer (R = 140,000 @200 〈em〉m/z〈/em〉) allowed separation of CPs signals of interest from unwanted halogenated ones, leading to minimum interferences in the detection. The optimised method was then successfully applied to the characterization of three types of vegetable oil, which were mostly contaminated with MCCPs. Additionally, the implementation of the LC-HRMS strategy enabled the identification of highly chlorinated LCCPs in edible oil for the first time at dozens of ng.g〈sup〉-1〈/sup〉 lw, which demonstrates the need of such comprehensive methods to expand the knowledge about CPs occurrence in food and environmental matrices.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 25 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Patrick O. Helmer, Carina M. Wienken, Ansgar Korf, Heiko Hayen〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The anionic phospholipid class of cardiolipins (CL) is increasingly attracting scientific attention in the recent years. CL can be found as a functional component of mitochondrial membranes in almost all living organisms. Changes in the CL composition are favored by oxidative stress. Based on this finding, the investigation of CL and their oxidation products in relation to various disease patterns, including neurodegenerative ones, is moving into the focus of current research. The analysis of this diverse lipid class is still challenging and requires sensitive and selective methods. In this work, we demonstrate an online two-dimensional liquid chromatography (LC) approach by means of a heart-cut setup. In the first dimension, a fast hydrophilic interaction liquid chromatography (HILIC) method was developed for the separation of CL and their oxidation products from other phospholipid classes, but more important from nonpolar lipid classes, such as triacylglycerol and cholesterol. Those classes can negatively affect the electrospray ionization and also the chromatography. For the heart-cut approach, the CL fraction was selectively transferred to a loop using a six-port valve followed by the transfer to a reversed phase (RP) column in second dimension. On the RP column, the transferred CL fraction including the oxidation products were separated according to the hydrophobicity of acyl chain moieties. Matrix effects were significantly reduced compared to the one-dimensional LC-MS method. In addition, the total separation time had not to be prolonged by shifting the equilibration step of the RP column parallel to the separation in first dimension. The heart-cut LC-LC approach was applied to artificially oxidized lipid extracts of bovine heart and yeast by means of Fenton reaction. In summary, 42 species have been identified by high resolution mass spectrometry and database matching. 31 species thereof have been further characterized by MS/MS experiments.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 23 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Shanshan Zhao, Chaoyue Wang, Xiang Wang, Yang Jin, Wenyu Sun, Xingchu Gong, Shengqiang Tong〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A method for sample pretreatment using liquid-liquid chromatography combined with a conventional liquid chromatography was developed for quantitative determination of trace chemical components in traditional Chinese medicine. The main effective component, wilforlide A, in the traditional Chinese medicinal herb 〈em〉Tripterygium wilfordii〈/em〉 as well as in its Chinese patent medicine glycosides tablets was successfully determined after sample pretreatment by liquid-liquid chromatography. A biphasic solvent system 〈em〉n〈/em〉-hexane-ethyl acetate-ethanol-water (6:4:6:4, v/v) was screened for crude sample treatment by liquid-liquid chromatography. The collection time of eluted fractions containing target components could be well predicted using a continuous-stirred tank reactors model after determination of its retention time. Then, quantitative analysis of wilforlide A in 〈em〉Tripterygium wilfordii〈/em〉 as well as in its tablets could be successfully determined by conventional reversed-phase high performance liquid chromatography with UV detector. Under the optimized conditions, the method showed good linearity (R〈sup〉2〈/sup〉 =0.9999) for wilforlide A in the range of 0.01 mg mL〈sup〉−1〈/sup〉 -0.10 mg mL〈sup〉−1〈/sup〉. The limit of detection and limit of quantity were 1.35 ng mL〈sup〉−1〈/sup〉 and 4.50 ng mL〈sup〉−1〈/sup〉, respectively. The average recovery rate, intra-day and inter-day precisions of wilforlide A were 96.43 %, 0.67 % and 1.14 %, respectively. Compared with previous studies, the present method showed advantages of complete recovery of target component in the sample pretreatment and good repeatability.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 23 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Raúl González-Martín, Idaira Pacheco-Fernández, Binoy Maiti, Juan H. Ayala, Ana M. Afonso, David Díaz Díaz, Verónica Pino〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A pH-sensitive polymer based on the poly(styrene-〈em〉alt〈/em〉-maleic anhydride) co-polymer serves as basis to develop a microextraction method (pH-HGME) in direct combination with high-performance liquid chromatography (HPLC) and fluorescence detection (FD) for the determination of seven organic compounds, including three polycyclic aromatic hydrocarbons (PAHs), three monohydroxylated PAHs and one alkylphenol, in urine. The method bases on the structural modification of the pH-sensitive polymer in the aqueous sample at a high pH value, followed by the formation and insolubilization of a hydrogel containing the preconcentrated analytes by decreasing the pH, and the direct injection of the hydrogel-rich phase in the HPLC-FD system. The optimization of the main variables permitted the selection of low amounts of aqueous sample (10 mL), which was mixed with 10 mg of co-polymer also present in a low volume (150 µL) of concentrated NaOH. The method further requires the addition of 200 µL of concentrated HCl, 3 min of stirring, and 15 min of centrifugation. This pH-HGME-HPLC-FD method presented low limits of detection, ranging from 0.001 µg•L〈sup〉−1〈/sup〉 to 0.09 µg•L〈sup〉−1〈/sup〉 in ultrapure water, average relative recoveries of 96.9% for the concentration level of 0.60 µg•L〈sup〉−1〈/sup〉, and enrichment factors between 1.50 and 17.7. The proposed method also exhibited high precision, with intermediate relative standard deviations lower than 16% for a concentration level of 0.60 µg•L〈sup〉−1〈/sup〉. The developed pH-HGME-HPLC-FD method performed adequately when analyzing two human urine samples provided by a non-smoker male and a smoker female, respectively. One of the target analytes (2-hydroxynaphthalene) was quantified in both samples using the standard addition method, with a predicted concentration of 7.3 ± 0.4 µg•L〈sup〉−1〈/sup〉 in the non-smoker male urine and 19.3 ± 0.6 µg•L〈sup〉−1〈/sup〉 in the smoker female urine.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 23 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Larry Miller, Shawn J. Ayube〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Volume overload is a critical limitation in Reversed Phase (RP)-HPLC purification of pharmaceutical compounds. Limited solubility of these materials in most injection solvents leads to large injection volumes in order to maximize throughput. However, peak distortion due to volume overload limits injection amounts, and results in suboptimal use of chromatographic instruments. Volume loading for RP gradient separations was significantly increased by inserting a silica column ahead of the RP separation column. The sole purpose of this column is to dilute the plug of strong injection solvent so that the actual sample constituents are retained when the diluted injection plug arrives at the RP column. This is similar to the concept of a “retention gap” in GC, yet this has never been applied to liquid chromatographic separations. Injection volumes were increased by almost a factor of 3 when using appropriately sized silica columns. A discussion of critical parameters that determine the effectiveness of this approach is provided. The concept is easily applied and does not require any system modifications. It is therefore well suited for open access applications where more instrument intensive approaches, such as “At-Column Dilution”, would be less desirable. We will also show that the generic concept which we have titled “In-Column Dilution” can easily be applied to increase the detection sensitivity for analytical application as well by allowing injection of larger sample volumes without peak deterioration for purifications.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 23 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Klaus Schilling, Ulrike Holzgrabe〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉High performance liquid chromatography (HPLC) methods with UV/vis detection are the most widespread analytical procedures in modern pharmaceutical applications, but reach their limitations when it comes to non-chromophore molecules. Hence, instead of using tiresome derivatization procedures, many liquid chromatography methods make use of the so-called aerosol-based universal detectors, namely the evaporative light scattering detector (ELSD), the condensation nucleation light scattering detector (CNLSD) and the charged aerosol detector (CAD). Amongst these, the CAD, being the youngest (introduced in 2005) of these three options, is often described as the most easy-to-use detector and is stated to exhibit sufficient sensitivity and good linearity of signal in a dedicated range of concentration. Therefore, this review sets its focus on the recent applications of the CAD for active pharmaceutical ingredients, excipient analysis as well as botanical applications. Alongside the post-column solvent addition techniques, the new CAD's ability to adjust the evaporation temperature and the possibility to use an integrated power function for signal linearization are reviewed as previously unavailable, new parameters for optimization.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 23 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Anna Klimek-Turek, Marika Michalska, Aleksandra Chwalczuk, Tadeusz H. Dzido〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Solvent Front Position Extraction (SFPE) procedure has been recently introduced as a novel concept for multi-component sample preparation. According to the procedure, thin-layer chromatography (TLC) is used to separate the compounds of interest from matrix components, and to focus them into a common zone from which the compounds are extracted and transferred to apparatus for instrumental analysis. In the paper, we investigate different adsorbent types of the chromatographic plates and various mobile phases, including pH of their buffers, in respect of optimization conditions of the SFPE procedure. The research was carried out using a test sample containing 9 compounds characterised by different chemical properties, hence the conclusions from the obtained results can be applied to other multi-component samples. Under the optimal conditions, all target compounds are separated from other compounds (matrix), and evenly distributed along a narrow strip, which is advantageous for their quantitation. The determination results are good, the percentage values of relative error and relative standard deviation do not exceed 6%.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 17 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Wei Jia, Qingyun Shi, Lin Shi, Junzhe Qin, James Chang, Xiaogang Chu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉During a microbial fermentation process, the chemical composition of Fu brick tea changed substantially. To better profile the unique changes of metabolites and lipids in Fu brick tea at different fermentation stages, a multifaceted strategy combining untargeted foodomics with UHPLC-Q-Orbitrap analysis was developed. The discriminative tea metabolites and lipids were determined by statistical analysis and online database matching. A total of 12 characteristic components (3 metabolic and 9 lipid variables) were found to differ significantly among samples. Quantitative analysis showed that, except for trimyristin and incensole acetate, the content of these compounds gradually increased and finally stabilized with increasing fermentation time. The simultaneous determination of metabolites and lipids in this study provided detailed information for the analysis of multi-component changes in a complex matrix.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 17 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Ivan A. Titaley, Ulrika Eriksson, Maria Larsson〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Complex chemical mixtures found in soils at contaminated sites typically includes polycyclic aromatic compounds (PACs), thus posing potential environmental and human health risks. Pressurized liquid extraction (PLE) followed by silica clean-up is one of the most often used extraction methods for PACs in soil. While silica clean-up provide satisfactory recovery of oxygenated polycyclic aromatic hydrocarbons (OPAHs), this technique provides limited recovery of azaarenes. In this work, we used PLE and in-cell clean up with basic silica to increase the recovery of OPAHs and azaarenes. The optimized selective pressurized liquid extraction (SPLE) method used 4 g basic silica, dichloromethane, 100% flush volume, 100 and 120°C extraction temperatures, with two static cycles for each temperature, no rinse in between the two extractions, and 20 and 120 s purge for the first and second extraction temperature, respectively. The method was validated for a wide range of PAC groups, including OPAHs, azaarenes, alkylated PAHs, and sulfur heterocycles (SPACs), in total 87 PACs, using certified reference material and in comparison to the results from previous inter-laboratory data. Our SPLE method yielded results that are in agreement with certified values and inter-laboratory data from prior analysis. The SPLE method also yielded lower variation than the results from the inter-laboratory data for analysis of OPAH and azaarenes, suggesting better precision than previous methods. More importantly, the SPLE method increases sample analysis throughput as extra clean-up step is not necessary anymore. The SPLE method was then successfully applied to rapidly screen PACs in three soil samples.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 15 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): William E. Acree, Brittani Churchill, Michael H. Abraham〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Abraham model correlations reported by Marlot and coworkers for the 1-octanol/water, 1-butanol/water, ethyl acetate/water, and heptane/methanol biphasic partitioning systems are compared to previously published Abraham model correlations. The previously published correlations for the fore-mentioned partitioning systems are based on more experimental data points, and exhibit much better descriptive ability as evidenced by much smaller standard deviations/standard errors and larger squared correlation coefficients.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 13 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Jie Gao, Guoying Luo, Zhan Li, Hui Li, Liang Zhao, Hongdeng Qiu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A new strategy for the preparation of mixed-mode chromatographic stationary phases based on modified dialdehyde cellulose was proposed. Two novel mixed-mode chromatographic stationary phases, dicarboxyl cellulose-modified silica (DCC/SiO〈sub〉2〈/sub〉) and (S)-α-phenylethylamine-bonded DCC/SiO〈sub〉2〈/sub〉 ((S)-α-PEA/DCC/SiO〈sub〉2〈/sub〉), were prepared by utilizing the easy functionalization characteristics of dialdehyde cellulose. The chromatographic evaluation showed that DCC/SiO〈sub〉2〈/sub〉 column could be used in hydrophilic interaction liquid chromatography (HILIC) and ion exchange chromatography (IEC) modes, (S)-α-PEA/DCC/SiO〈sub〉2〈/sub〉 column could be used in HILIC, IEC and chiral separation modes. The DCC/SiO〈sub〉2〈/sub〉 column and (S)-α-PEA/DCC/SiO〈sub〉2〈/sub〉 column exhibited excellent chromatographic performance by separating strongly polar compounds, phenylamines and chiral compounds in the above separation modes. The preparation method of modified dialdehyde cellulose-based mixed-mode chromatographic stationary phases was simple, and also provided a new idea for the development of the subsequent novel mixed-mode chromatographic stationary phases.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 13 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Marie-Jia Gou, Gwenaël Nys, Gaël Cobraiville, Alice Demelenne, Anne-Catherine Servais, Marianne Fillet〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Capillary electrophoresis tandem mass spectrometry (CE-MS/MS) is an interesting tool for proteomic analysis as the separation principle is orthogonal to liquid chromatography tandem mass spectrometry (LC-MS/MS). The combination of both techniques can bring complementary information to enlarge proteome coverage.〈/p〉 〈p〉In this study, sample preconcentration techniques were investigated in order to improve sample loading and therefore sensitivity. Dynamic pH junction (DPJ) was found to be the most interesting approach by using 200 mM ammonium acetate (NH〈sub〉4〈/sub〉Ac) adjusted to pH 10.0 as sample matrix. The use of DPJ allowed the identification of more peptides and proteins compared to conventional injections. Moreover, the sheath liquid (SL) composition was optimized in order to enhance signal intensity.〈/p〉 〈p〉A nanoflow SL interface (EMASS-II) was compared to the traditional coaxial SL interface (Triple tube) in terms of number of identified and proteins as well as detection sensitivity (peak area and peak height). MS acquisition was performed using both data-dependent acquisition (DDA) and data-independent acquisition (DIA) modes. The results showed that the combined use of these two acquisition modes provided additional information in terms of identification. Moreover, the use of EMASS-II interface allowed the identification of approximately two times more peptides and proteins. Besides, there was an improvement in sensitivity using EMASS-II as peak height and peak area were improved by 4 and 6-fold, respectively, compared to the Triple tube. Altogether, by combining an efficient sample preconcentration method, a nanoflow CE-MS interface and a hybrid ion-mobility qTOF mass spectrometer, a satisfying sequence coverage was obtained by analyzing 1 µg of 〈em〉E. coli〈/em〉 proteome digest.〈/p〉 〈/div〉

Description: 〈p〉Publication date: Available online 13 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Xiudan Hou, Hui Yu, Shihai Yan, Junxia Xiao, Min Sun, Wei Wu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The facile preparation and characterization of a cationic polyelectrolyte (polydiallyldimethylammonium chloride, PDDA) fabricated graphene oxide-grafted silica microsphere (PDDA@GO@Sil) with high positive charge density as the sorbent for the high selective capture of acidic herbicides were reported. The theoretical calculation showed that there were strong adsorption energies between the PDDA and analytes, and the main interaction was the hydrogen bonding from O〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉H…Cl and C〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/dbnd"〉O…H〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉C. Static- and dynamic- state adsorption results indicated that acidic herbicides were the monolayer coverage onto the PDDA@GO@Sil due to the electrostatic attraction between the sorbent and analytes, and electrostatic repulsion among analytes. Under the optimized conditions obtained with the single-factor experiment and response surface methodology, this established method was used for the enrichment and determination of herbicides in two vegetables. Method detection limits were in the range of 0.75–1.50 µg L〈sup〉−1〈/sup〉 indicating that the introduction of PDDA provided the excellent extraction capacity toward acidic herbicides. The obtained results exhibited that the developed method was feasible, reliable, selective and accurate for the determination of acidic herbicides in real samples.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 13 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Zhixia Huo, Qian-Hong Wan, Lei Chen〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉An energy-efficient and environment-friendly approach to prepare porous monodispersed micro-sized silica particles with methyltrimethoxysilane (MTMS) as the precursor is described. The particles were synthesized by a two-step hydrolysis/condensation procedure, with post-synthetic aging and calcination for methyl group removal. They show uniform spherical morphology, narrow particle size distribution (D〈sub〉90〈/sub〉/〈sub〉10〈/sub〉, 1.2–1.6), tailored particle size (3, 5, 7 μm) and mesopore structure (10, 13 nm), which can be directly used as packing materials for HPLC without size classification. C〈sub〉18〈/sub〉, sulfonate, and C〈sub〉18〈/sub〉/sulfonate mixed-mode stationary phases were produced by a green vapor deposition method based on the synthesized silica particles. The newly synthesized C〈sub〉18〈/sub〉 phase exhibits mechanical stability, kinetic behavior and separation performance expected from the commercial C〈sub〉18〈/sub〉 column. The C〈sub〉18〈/sub〉/sulfonate phase exhibits prominent mixed-mode retention behavior which can be applied to the simultaneous separation of multiple substances in the compound drugs.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 13 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Kaige Zhang, Shuangying Li, Yunhe Wang, Jing Fan, Guifen Zhu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉For this work, a novel air-assisted liquid-liquid microextraction based on solidification of floating deep eutectic solvent (AA-LLME-SFDES), coupled with a high performance liquid chromatography (HPLC) method was developed for the detection of benzophenone and salicylate ultraviolet filters in water samples. Three types of fatty acid-based hydrophobic deep eutectic solvents (DESs) with low viscosity, low-density, and melting point close to room temperature were prepared and employed as extraction solvents. This air-assisted liquid-liquid microextraction was carried out in a glass centrifuge tube. Subsequently, the glass tube was introduced into ice-water bath and held for 3 min, during which the upper DES phase was solidified. The water phase was easily extracted using a syringe equipped with a long needle, and later, the glass tube was removed from ice-water bath. The solidified DES phase was immediately melted at room temperature and used for HPLC analysis. The response surface methodology was employed to optimize some influencing parameters such as the volume of the extraction solvent, the pH value of sample solution, the number of extraction cycles, and the addition of salt. A quadratic model, namely a central composite design, was used to replace the conventional single factor analysis. It was found that under optimal conditions, the limits of determination and quantification were 0.045–0.54 µg L〈sup〉−1〈/sup〉 and 0.15–2.0 µg L〈sup〉−1〈/sup〉, respectively. The relative standard deviations for inter-day (〈em〉n〈/em〉 = 5) and intra-day (〈em〉n〈/em〉 = 5) precision were ≤ 4.2%, whereas the enrichment factors for the ultraviolet filters were obtained from 41 to 50. Furthermore, this novel method was successfully employed for the detection of benzophenone and salicylate ultraviolet filters from real water samples. The recoveries ranged from 87.5% to 105.8%, whereas the RSDs were lower than 3.6%.〈/p〉〈/div〉

Description: 〈p〉Publication date: 11 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1610〈/p〉 〈p〉Author(s): 〈/p〉

Description: 〈p〉Publication date: Available online 12 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Yoachim Vanderheyden, Ken Broeckhoven, Gert Desmet〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉The present contribution reports on the practical implementation and validation of a new experimental method to determine the radial dispersion (D〈sub〉rad〈/sub〉) in packed bed liquid chromatography columns, as well as on the results obtained with it. A first important validation was that the measured D〈sub〉rad〈/sub〉-values were independent of the applied relative central flow rate (varied from 25% to 57%). The obtained D〈sub〉rad〈/sub〉-values did not vary significantly when changing the concentration of the injected tracer to check potential mass overloading effects (25, 50 or 75 ppm of tracer for the acetophenone measurements; 12.5 and 25 ppm of tracer for the toluene measurements). And yet another important validation step was the observation that the D〈sub〉rad〈/sub〉-values clearly converged to the value of D〈sub〉eff〈/sub〉 for velocities going to zero, as physically and theoretically expected.〈/p〉 〈p〉Plotting the obtained results as a plot of D〈sub〉rad〈/sub〉/D〈sub〉mol〈/sub〉 versus the reduced velocity ν, a quasi-linear relationship is obtained. The slope of the curve (β = 0.38 and β = 0.46 for toluene and acetophenone, respectively) is significantly larger than the value that is most frequently cited in engineering literature. However, the obtained β-values and D〈sub〉rad〈/sub〉/D〈sub〉mol〈/sub〉-values still fall within the broad range of β- and D〈sub〉rad〈/sub〉/D〈sub〉mol〈/sub〉-values cited in literature.〈/p〉 〈/div〉

Description: 〈p〉Publication date: Available online 15 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Davy Guillarme, Caroline West〈/p〉

Description: 〈p〉Publication date: 25 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A, Volume 1611〈/p〉 〈p〉Author(s): 〈/p〉

Description: 〈p〉Publication date: Available online 15 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Martina Komendová, Jiří Urban〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Seven retention models have been selected to describe a dual-retention behavior of ten dopamine-related compounds on polymer-based monolithic stationary phase with zwitterion sulfobetaine functionality. Regression quality, as well as a statistical significance of individual regression parameters, have been evaluated. Better regression performance showed two four-parameter models when compared to three-parameter models. On the other hand, limited number of experimental points disqualified statistical robustness of four-parameter models. Among three-parameter models, retention description introduced by Horváth and Liang provided comparable quality of regression at significantly improved robustness.〈/p〉 〈p〉Multivariate analysis of the best three-parameter models provided the description of physicochemical properties of dopamine precursors and metabolites. Principal component analysis and logistic regression allowed structural characterization of dopamine-related compounds based solely on regression parameters extracted from an isocratic elution data. Both polarity and type of functional groups has been correctly assigned for 3-methoxytyramine that has not been part of an evaluation study. Among applied dual-retention models, Horváth´s model, initially developed to describe a retention of ionic compounds on nonpolar stationary phases, provided robust regression of experimental data and allowed an extraction of structural characteristics of dopamine-related compounds〈/p〉 〈/div〉

Description: 〈p〉Publication date: Available online 15 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Raja Ghosh, Guoqiang Chen, Umatheny Umatheva, Paul Gatt〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We discuss how the efficiency of a chromatography device could be enhanced by incorporating a new feature which ensures flow uniformity. The overall flow of fluid within the device, which has a cuboid shape, could be visualized as a combination of two z patterns. The device is therefore designated as cuboid z〈sup〉2〈/sup〉. The reason for flow uniformity is explained using a simple mathematical model, and based on computational fluid dynamic (CFD) simulations. The cuboid z〈sup〉2〈/sup〉 device substantially outperformed its equivalent column in terms of separation efficiency metrics such as the number of theoretical plates, reduced plate height, and attributes of non-interacting solute tracer peaks. The results discussed in this paper clearly indicate the suitability of using the cuboid z〈sup〉2〈/sup〉 device for high-resolution chromatographic separations. The z〈sup〉2〈/sup〉 flow enhancing feature would also be broadly applicable to any situation requiring uniform flow in three-dimensional porous media. In addition to superior fluidic attributes, the cuboid z〈sup〉2〈/sup〉 device is expected to have other advantages such as compactness and scalability.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 21 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Xiujun Ren, Qiurong Luo, Di Zhou, Kailian Zhang, Die Gao, Qifeng Fu, Jun Liu, Zhining Xia, Lujun Wang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A novel chiral stationary phase (CSP) was prepared through the reaction of surface-initiated atom transfer radical polymerization (ATRP) by the copolymerization of thermoresponsive 〈em〉N〈/em〉-isopropylacrylamide (NIPAM) and β-cyclodextrin (β-CD) on the silica beads for high performance liquid chromatography (HPLC). X-ray photoelectron spectroscopy (XPS), elemental analysis (EA), Fourier transform infrared spectrometry (FT-IR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) were applied to characterize the surface property of modified silica. Thermoresponsive modulation for the effect on enantioselectivity were investigated with chiral reagents including 1-phenyl-1-propanol, styrene oxide, 2-phenylpropionic acid and commercial chiral drugs comprising ibuprofen and labetalol hydrochloride. The column efficiency was evaluated by chromatographic parameters including retention factor (k), selective factor (α), resolution (R〈sub〉s〈/sub〉), plate number (N) and peak tailing factor (T〈sub〉f〈/sub〉). The results showed that five chiral solutes could be separated on the prepared smart column. And the selectivity of these compounds could be modulated by regulating the column temperature. It was contributed to the thermoresponsive NIPAM assisting β-CD to separate these chiral compounds. These results indicated that the thermoresponsive CSP would be a potential tool for separation of hydrophilic and hydrophobic chiral drugs and this paper provided a novel method for chiral separation in the future.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 22 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Ingrid Guiffard, Thomas Geny, Bruno Veyrand, Philippe Marchand, Anne Pellouin-Grouhel, Bruno Le Bizec, Emmanuelle Bichon〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The aim of our work was to develop an analytical strategy to quantify naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene and anthracene in fish products by on-line dynamic headspace extraction, followed by thermodesorption injection and gas chromatography analysis coupled with tandem mass spectrometry using electron ionization mode (DHS-TD-GC-EI-MS/MS). The developed protocol used 1 g of freeze-dried or oil sample supplemented with perdeuterated light PAHs. The sample was heated at [90 –100 °C], the headspace of the sample was swept by nitrogen and the trapping of the PAHs was carried out on a Tenax-type adsorbent placed at 25 °C. Analytes were thermodesorbed at 300 °C from the dried adsorbant and then cryofocused on a cooled injection system (CIS) at −25 °C before injection (12 °C s〈sup〉−1〈/sup〉 up to 300 °C). The chromatographic separation of PAHs was carried out on a 5-MS type column (30 m × 0.25 mm, 0.25 μm) and the acquisition of the signals was performed in SRM following the transitions, involving the loss of one or two hydrogen atoms from the molecular ion. In view of the principle of extraction, the calibration curve was performed on a representative matrix or using the standard addition method. Quantification limits were determined between 0.01 and 0.6 ng g〈sup〉−1〈/sup〉 of matrix from the method blank results. The method was validated by a series of multi-level supplemented matrix assays and by the analysis of a reference material from an inter-laboratory test (mussels, IAEA-432). The average of the expanded measurement uncertainty was from 9 to 44% for the four lightest PAHs, except for fluorene when the sample incubation was set at 90 °C. Occurrence measurements were performed on almost two hundred samples of molluscs, echinoderms and fish. The results have shown a quantification frequency greater than 66% for naphthalene and fluorene, at concentrations below a few ng g〈sup〉−1〈/sup〉 of dry matter of fishery products. With this methodology, the light PAHs occurrence can now be measured in a wider range of foodstuffs in order to better characterize their contamination trends and the associated risk simultaneously.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 18 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Junyu Lu, Rui Wang, Jingyi Luan, Yijun Li, Xiwen He, Langxing Chen, Yukui Zhang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A functionalized magnetic covalent organic framework containing the nitro groups (Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉@COF-(NO〈sub〉2〈/sub〉)〈sub〉2〈/sub〉) with core-shell structure was synthesized for magnetic solid phase extraction (MSPE) of six neonicotinoid insecticides residue in vegetable samples. The structure of Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉@COF-(NO〈sub〉2〈/sub〉)〈sub〉2〈/sub〉 was investigated by various characterization techniques. The Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉@COF-(NO〈sub〉2〈/sub〉)〈sub〉2〈/sub〉 exhibits the excellent thermal and chemical stability, high surface area (254.72 m〈sup〉2〈/sup〉•g〈sup〉−1〈/sup〉), total pore volume (0.19 cm〈sup〉3〈/sup〉•g〈sup〉−1〈/sup〉), high magnetic responsivity (27.7 emu•g〈sup〉−1〈/sup〉), which can be used as an ideal adsorbent for rapid isolation and enrichment of target analytes. A sensitive method was developed by using Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉@COF-(NO〈sub〉2〈/sub〉)〈sub〉2〈/sub〉-based MSPE coupled with HPLC with UV detection. It offered good linearity within the range of 0.1-30 ng•mL〈sup〉−1〈/sup〉, low limits of detection (S/N=3) of 0.02-0.05 ng•mL〈sup〉−1〈/sup〉. Furthermore, high enrichment factors of 170-250 for six neonicotinoid insecticides were obtained. The applicability of Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉@COF-(NO〈sub〉2〈/sub〉)〈sub〉2〈/sub〉 is demonstrated for measuring trace neonicotinoid residues in vegetable samples with satisfactory recoveries, which ranged from 77.5 to 110.2 %. The results indicated that the Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉@COF-(NO〈sub〉2〈/sub〉)〈sub〉2〈/sub〉 microspheres offer great potential for efficient extraction of neonicotinoid insecticides from complex samples.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 18 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Leila Josefsson, David Goodall, Åsa Emmer〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Contrast agents are widely used to enhance the image quality in clinical imaging using 〈em〉e.g.〈/em〉 ultrasound. The contrast agents used for ultrasound imaging are mainly microbubbles (MBs) with a soft or hard shell encapsulating a core of gas. In the present study, MBs with a hard shell of polyvinyl alcohol (PVA), and a core of air were analysed in a capillary electrophoretic system using a UV area imaging detector. The detector was operating at 3 wavelengths; 214 nm, 255 nm and 525 nm, and the highest absorbance for individual PVA-MBs were obtained at 214 nm. Two detection windows and a vertical loop capillary position enabled tracking of the PVA-MBs both in an upward and a downward flow direction, where PVA-MBs had different flow distributions and slightly higher average flow velocity upwards, attributed to temperature differences in the capillary that was part within the instrument and part outside. The tracking also allowed counting and quantification of the PVA-MBs. Separation of PVA-MBs from proteins present in human blood plasma was achieved, with multi-wavelength imaging showing best contrast at 525 nm. The PVA-MBs absolute values of negative zeta potential and anionic mobility when injected from plasma in the pH 12 background electrolyte are higher than those obtained for MBs injected from buffer, consistent with their increased negative charge due to a protein corona coating of the PVA-MBs.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 21 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Zdena Malá, Petr Gebauer〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This work extends the present working range of isotachophoresis (ITP) with electrospray-ionization mass-spectrometric (ESI–MS) detection and describes for the first time a functional cationic electrolyte system for analyses at medium-alkaline pH. So far no ITP–MS application was published on the analysis of medium strong bases although there is a broad spectrum of potential analytes like biogenic amines, alkaloids or drugs, where this technique promises interesting gains in both sensitivity and specificity. The presented results include a selection of suitable sufficiently volatile ESI-compatible system components, discussion of factors affecting system properties, and recommendations for functional ITP electrolyte systems. Theoretical conclusions based on calculations and computer simulations are confirmed by experiments with a model mixture of beta-blockers. Practical applicability of the method is demonstrated on the example of analysis of sotalol in dried blood spots where direct injection of aqueous extract, ITP stacking and MS detection provide a fast, simple and sensitive technique with limits of quantitation on the sub-nM level.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 21 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Qirui Bi, Qiao Liu, Sha Han, Lu Zhang, Longsheng Xing, Xuejia Zhang, Zhe Wang, Yuanyuan Miao, Ninghua Tan〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Complexity and diversity of natural compounds make it a challenge for globally profiling constituents in multiple species plants, especially for minor new compounds. Rubiaceae-type cyclopeptides (RAs) are one kind of active constituents and characteristic components in 〈em〉Rubia〈/em〉 plants, particularly 〈em〉Rubia cordifolia〈/em〉 (RC), which is one kind of traditional Chinese medicines. In this study, a new multiple reaction monitoring strategy (PPCP-MRM) based on predicted precursor ions and characteristic product ions was developed to globally profile RAs in RC and its two main adulterants, including 〈em〉Rubia alata〈/em〉 (also named Jinjiancao in Chinese) (RAJ) and 〈em〉Rubia podantha〈/em〉 (RP). Moreover, characteristic components of these species have been found by targeted relative quantitative analysis of RAs by LC-MS. In total, 39 RAs have been structurally annotated based on fragment ions in MS〈sup〉2〈/sup〉 data, including 19 new compounds. In addition, 7 RAs as the chemical markers were found to distinguish these three 〈em〉Rubia〈/em〉 species. The results indicated that this PPCP-MRM integrated strategy is a powerful tool for comprehensive analysis of RAs and screening chemical markers for 〈em〉Rubia〈/em〉 species discrimination, which would be useful for distinguishing 〈em〉Rubia〈/em〉 adulterants. Furthermore, this developed strategy could also be a useful tool for analysis of other cyclopeptides.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 21 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Szabolcs Fekete, Harald Ritchie, Jason Lawhorn, Jean-Luc Veuthey, Davy Guillarme〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A novel column-coupling approach is suggested to improve both the selectivity and efficiency of protein separations in liquid chromatography. Protein separations often suffer from limited selectivity or not appropriate resolving power. For a new biopharmaceutical product, the identification of the main and minor variant species is required. For that purpose, often offline collection fractioning is applied which is time consuming and regularly dilute the samples to an unacceptable extent. By serially coupling columns in the order of their increasing retentivity and applying “multi-isocratic” elution mode, indeed any (arbitrary) selectivity can be attained. Moreover, if a protein peak is trapped at the inlet of a later column segment – of a coupled system -, its band will be refocused and elute in unprecedented sharp peak. Furthermore, it becomes possible to perform online on-column fractioning of protein species within a very short analysis time (∼ 1 min) and without sample dilution. Two-, three- or multiple column systems can be developed and applied for complex sample separations (such as antibody mixtures). This new methodology can be particularly useful to improve the analysis (and therefore, safety and quality) of therapeutic mAbs and related products and offers benefits compared to offline fractionating. It is also demonstrated in this proof of concept study, that methyl (C1) modified RP phase has a great potential for protein separations despite it is not commercially available in state-of-the-art wide pore superficially porous particle format..〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 21 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Xiao-Hua Zhang, Qian Zhou, Zhi Liu, Xiang-Dong Qing, Jing-Jing Zheng, Shu-Ting Mu, Pan-Hua Liu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Retention time shifts in second-order calibration-assisted chromatographic analysis seriously impact the modeling and quantitative accuracies in complex systems. In this work, three second-order methods, i.e. alternating trilinear decomposition (ATLD) algorithm, multivariate curve resolution-alternating least squares (MCR-ALS), alternating trilinear decomposition-assisted multivariate curve resolution (ATLD-MCR), were compared their performance to process liquid chromatographic data in the presence of retention time shifts and overlapped peaks. Firstly, the validation samples contain five tea polyphenols at three concentrate levels within the calibration ranges, helped to understand, visualize and interpret these features of three second-order multivariate methods. Secondly, experimental data were studied concerning the determination of polyphenols in Chinese tea samples by HPLC-DAD. The results showed that all three second-order multivariate methods realized satisfactory quantification for five targeted analytes in Pu-Er ripe tea samples and Green tea samples even with the interference of slight retention time shifts, average recoveries were 91.23% -113.16% for ATLD, 89.96%-115.96% for ATLD-MCR, 90.64%-117.60% for MCR-ALS, respectively. However, ATLD was disappointing in the case of larger time shifts (approx. 4.00 s and 6.40 s) occurring for the quantitative analysis of Black tea and Clinacanthus nutans tea, the average recoveries were just 67.33-84.05%. Relatively, MCR-ALS and ATLD-MCR were more significantly excellent, satisfactory results still can be obtained, the average recoveries for MCR-ALS and ATLD-MCR were in the range of 86.04-117.60% and 89.96-115.96%, respectively.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 16 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Heather Wang, Hayley R. Lhotka, Raffeal Bennett, Miraslava Potapenko, Chad J. Pickens, Benjamin F. Mann, Imad A. Haidar Ahmad, Erik L. Regalado〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Baseline separation and analysis of multicomponent mixtures of closely related pharmaceuticals using a single column selectivity can often be challenging, requiring the combination of orthogonal stationary and mobile phase methods to monitor all the species and optimize reaction outcomes. In recent years, two-dimensional liquid chromatography (2D-LC) has become a valuable tool for improving peak capacity and selectivity. Though powerful, standard 2D-LC instrumentation and software can often lead to tedious method development and has a requirement for very specific expertise that is poorly suited for a fast-paced industrial environment. In this regard, the introduction of an automated online 2D-LC setup that could screen multiple columns in both dimensions without manual intervention will undeniably serve to streamline column/mobile phase selection and secure the viability of 2D-LC as a mainstay instrument for industrial applications. Herein, we introduce and investigate a multicolumn online 2D-LC approach that simplifies column screening and method development dramatically. This setup incorporates 6-position column selection valve technology whose functionality enables us to combine multiple columns in the first and second dimensions. This strategy in conjunction with diode array detection (DAD) in both dimensions and mass spectrometry (MS) acquisition in the second dimension serves to explore different columns and mobile phases as a framework for screening targeted compounds in multicomponent mixtures without having to perform chromatographic purification. Multiple online heartcutting achiral RPLC – achiral RPLC and achiral RPLC – chiral RPLC coupled to DAD and ESI-MS methods combining several stationary phase selectivity in an automated fashion are successfully applied to the separation and analysis of complex mixtures of drug substances, where in many instances, traditional 1D-ultra-high performance liquid chromatography (UHPLC) fails or delivers sub-optimal results. This automated online multicolumn 2D-LC workflow enables rapid and efficient identification of column/eluent combinations, as well as sample analysis across multiple column in both dimensions overnight with a single click.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 15 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Yun Zhang, Yong-Gang Zhao, Nadeem Muhammad, Ming-Li Ye, Yan Zhu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, three batches of nano-titania functionalized covalent organic frameworks were acquired depending on different solvothermal reaction stages (24 h, 48 h and 72 h), which were named as single roll-up shaped nano-titania functionalized COFs (SSTF-COFs), double roll-up shaped nano-titania functionalized COFs (DSTF-COFs) and clover-shaped nano-titania functionalized covalent organic framework (CSTF-COFs), respectively. After comparing their extraction performances, the more efficient and stable CSTF-COFs were selected as sorbent for the dispersive solid phase extraction (dSPE) of eight target N-nitrosamines in drinking water, followed by the determination with liquid chromatography-tandem quadrupole mass spectrometry (LC–MS/MS). Owing to the introduction of hydroxy groups, CSTF-COFs showed high extraction efficiency for N-nitrosamines with a wide range of polarities through hydrogen bonding interaction, hydrophobic interaction and hydrophilic interaction. Under optimum conditions, the developed method provided relatively low limits of detection (0.13–2.45 ng/L) and satisfactory recoveries (88.6–105.5%), with relative standard deviations (RSDs) less than 8.3%. Therefore, with the assistance of CSTF-COFs, trace levels of N-nitrosamines were quantitatively and sensitively determined in 31 out of 460 bottled drinking water samples in a sensitive and convenient way.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 15 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Nan Wang, Chunfeng Duan, Shenghong Li, Xuhui Geng, Kun Ding, Yafeng Guan〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A green sample preparation method based on aqueous extraction followed by dispersive solid phase extraction (d-SPE) with in situ derivatization (ISD) was developed for the determination of aflatoxins (AFs) in traditional Chinese medicines (TCMs). AFs in TCMs were extracted by alkaline aqueous solution and converted to substituted coumaric acids. Then, mixed-mode anion exchange (MAX) sorbent was used to isolate and enrich the substituted coumaric acids. During the elution by acetonitrile/trifluoroacetic acid solution, AFs were reconstructed and in situ derivatized. Several parameters affecting the procedure were evaluated. The developed preparation method coupled with high performance liquid chromatography-fluorescence detection was successfully applied for AFs determination in TCMs. The limit of detection (LOD) reached 10 pg/mL for AFs. Good linearity was obtained in three orders of magnitude with correlation coefficients ranging from 0.9996 to 0.9999. The relative recoveries of the method were between 72.7%-114.5% with intra- and inter-day relative standard deviations (RSDs) less than 9.5% and 10.1%, respectively. The method was successfully applied to determine AFs in 15 kinds of TCMs in China, with the results verified by IAC standard method.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 9 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Junliang Du, Rong Zhang, Feifei Wang, Xuemei Wang, Xinzhen Du〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Novel solid-phase microextraction fibers were fabricated by electrochemical deposition of cobalt on the pretreated nickel/titanium alloy (NiTi) fiber substrate and subsequent in situ growth of zeolitic imidazolate framework-67 (ZIF-67) followed by annealing treatment. The Co@ZIF-67 coating was used as a precursor and template for controlled fabrication of the Co@ZIF-67-derived coatings including Co@ZIF-67-Co〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 and carbonaceous composite coatings. . The extraction performance of the Co@ZIF-67-derived coatings was evaluated using typical aromatic compounds coupled to high-performance liquid chromatography with UV detection. The results clearly demonstrate that the extraction selectivity is subject to the surface elemental composition of the ZIF-67-derived coatings. In view of long-term stability and good extraction selectivity, the Co@ZIF-67-C coating was selected for the enrichment and determination of polycyclic aromatic hydrocarbons (PAHs). Under the optimized conditions, the calibration curves were linear in the range of 0.05-100 μg•L〈sup〉−1〈/sup〉 with the correlation coefficients above 0.998. Limits of detection were 0.005-0.042 μg•L〈sup〉−1〈/sup〉. Furthermore, the intra-day and inter-day repeatability of the proposed method with the single fiber varied from 2.3% to 5.8% and from 3.3% to 6.9%, respectively. The fiber-to-fiber reproducibility ranged from 4.1% to 8.5%. The proposed method was suitable for selective enrichment and determination of target PAHs from real water samples. Moreover, the fabricated fiber showed precisely controllable growth and 150 extraction and desorption cycles.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 9 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Leo Lebanov, Shiladitya Chatterjee, Laura Tedone, Sean C. Chapman, Matthew R. Linford, Brett Paull〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Analysis of the complex essential oil samples using gas chromatography hyphenated with mass spectrometry (GC-MS) generate large three-way data arrays. Processing such large data sets and extracting meaningful information in the metabolic studies of natural products, requires application of multivariate statistical techniques (MSTs). From the GC-MS raw data several different input data sets for the MSTs can be created, total chromatogram average mass spectrum (TCAMS), segmented average mass spectrum (SAMS) and chemical composition. Herein, we compared the performance of MSTs on average mass spectrum based data sets, TCAMS and SAMS, against chemical composition and attenuated total reflectance - Fourier transformation infrared (ATR-FTIR) spectroscopy in the evaluation of quality of ylang-ylang essential oils, based on their grade, geographical origin and chemical composition, using principal component analysis (PCA), partial least squares regression (PLS) and discriminatory analysis (PLS-DA). PCA based on TCAMS, SAMS and chemical composition showed clear trends amongst the samples based on increase in grade (distillation time). PLS-DA applied to TCAMS, SAMS and ATR-FTIR discriminated between all geographical origins. Predicted relative abundances of 18 most important compounds, using PLS regression models on TCAMS, SAMS and ATR-FTIR, were successfully applied to ylang-ylang essential oil quality assessment based on comparison with the ISO 3063:2004 standard, where SAMS data set showed superior performance, compared to other data sets.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 9 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Anthony Ndiripo, Harald Pasch〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The behavior of isotactic, syndiotactic and atactic polypropylene stereoisomers on porous graphitic carbon (PGC) at different column temperatures is investigated with 1-decanol, decalin and decane as the adsorption promoting solvents using gradient interaction chromatography (SGIC). Column temperatures between 120 – 180 °C are investigated for the three adsorption promoting solvents with 1,2,4-trichlorobenzene (TCB) as the desorption promoting solvent. Owing to the different stereochemistry of the isomers, their interaction with the atomic level flat surface (ALFS) of porous graphitic carbon is observed to be different when injected from the three different adsorption promoting solvents. Atactic and isotactic polypropylene are not separable when 1-decanol is used as the adsorption solvent but can be separated from syndiotactic PP at column temperatures of between 120 – 180 °C. The three stereoisomers have almost similar elution volumes when decalin is used as the adsorption promoting solvent between 120 – 170 °C. Decane allows for both adsorption and desorption of the stereoisomers at distinct peak elution volumes at the studied column temperatures of 120 – 160 °C. Furthermore, it is shown that increasing the column temperature while maintaining other chromatographic conditions can either decrease or increase retention depending on the adsorption promoting solvent. More importantly, retention is influenced by adsorption conditions (temperature and adsorption promoting solvent) which may affect macromolecular conformations upon injection onto the PGC stationary phase. This is the first study on PP stereoisomers highlighting this behaviour.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 3 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Jung Yong Eum, Jong Cheol Lee, Sun Shin Yi, Il Yong Kim, Je Kyung Seong, Myeong Hee Moon〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Aging refers to the intracellular accumulation of reactive oxygen species that damages proteins, DNA, and lipids. As alterations in lipid metabolism may trigger metabolic disorders and the onset of metabolic diseases, changes in lipid profiles can be closely related to aging. In this study, a comprehensive lipidomic comparison between 4- and 25-month-old mice was performed to investigate age-induced changes in the lipid profiles of mouse serum, kidney, and heart using nanoflow ultrahigh-performance liquid chromatography-electrospray ionization-tandem mass spectrometry. Quantitative analysis of 279 of the 542 identified lipids revealed significant changes upon aging, mainly showing decreased levels in the three types of samples. Exceptionally, most triacylglycerols showed significant increases in heart tissue. The kidney was influenced more by aging than the serum and heart. The highly abundant lipids in each lipid class with significant decreases (〉 2-fold, 〈em〉p〈/em〉 〈 0.01) were lysophosphatidic acid 18:1, lysophosphatidylinositol 20:4, and ceramide d:18:1/24:0 in serum; lysophosphatidylglycerol 16:0 in heart tissue; and eight phosphatidylethanolamines (20:4, 22:6, 36:2, 36:3, 38:4, 38:5, 38:6, 40:6, and 40:7), two cardiolipins (72:7 and 72:8), and lysophosphatidylcholine 18:0 in kidney tissue. The findings indicate the potential of lipidomic analysis to study characteristic age-related lipid changes.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 2 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): J. Escobar-Arnanz, M.L. Sanz, M. Ros, J. Sanz, L. Ramos〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉The aim of this study was to develop a statistical model based on a set of intuitive topological descriptors that will help to determine the influence of the polychlorinated biphenyls (PCBs) structural features on the chromatographic behavior of these analytes in a variety of gas chromatographic stationary phases, including the highly polar ionic liquid (IL)-based SLB-IL76 and SLB-IL60 columns. The model was developed using the stepwise multiple linear regression method, and constructed through several levels of increasing complexity to make evident the relative influence of the selected descriptors.〈/p〉 〈p〉The proposed model was easy to implement and provided similar satisfactory results irrespective of the dependent variables used (i.e., retention index or retention time) or the chromatographic conditions applied (i.e., pseudo-isotherm and programmed temperature) for IL-based phases. The model also allowed the correct prediction of the elution order of selected PCBs in these and other less polar phases evaluated (i.e., SW-10, DB-17, ZB-5 and HT-8). To our knowledge, this is the first models based on topological descriptors described in the literature that provided a satisfactory fitting of the PCB behavior in IL-based phases. Our results indicated that the mechanism governing the chromatographic separation of PCBs in these highly polar columns showed significant differences compared with those observed in other less polar stationary phases.〈/p〉 〈/div〉

Description: 〈p〉Publication date: Available online 2 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Feng Xu, Yao Xu, Guizheng Liu, Meng Zhang, Shangshang Qiang, Jingwu Kang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Posaconazole represents a triazole antifungal agent which is used to treat various fungal infections. It contains four chiral centers leading to 16 stereoisomers. With the convergent synthesis route, only 11 related stereoisomeric impurities may potentially exist in the active pharmaceutical ingredient (API). It is a challenge to separate all the stereoisomers in one run. To address this problem, a multiple heart-cutting chiral–chiral two-dimensional liquid chromatography (2D-LC) method was developed. The multiple heart-cutting 2D-LC separation was implemented on 2D-LC system with three chiral columns with immobilized polysaccharide chiral stationary phases, namely Chiralpak IB, IC and IF3. In the system, the column Chiralpak IB was used as the 〈sup〉1〈/sup〉D separation column and IC and IF3 columns were used parallelly for the 〈sup〉2〈/sup〉D separation. The twelve stereoisomers were all well separated in one run by the multiple heart-cutting chiral–chiral 2D-LC system.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 2 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): T.C. VandenBoer, R.A. Di Lorenzo, R.F. Hems, K.E.R. Dawe, S.E. Ziegler, C.J. Young〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A rapid separation and quantitation of the stereoisomer amino sugars glucosamine, galactosamine, and mannosamine, along with muramic acid, is needed. These compounds, when their quantities are accurate, can be used to understand the origin and fate of natural organic matter (NOM) in the environment. These target molecules are biomarkers of fungi and bacteria and allow the deconvolution of microbial transformations and degradation of NOM in a wide variety of environmental matrices. Analytical methods applied to this suite of biomarkers are needed to understand carbon and nitrogen biogeochemistry with a changing global climate. Traditional separations of these analytes by gas chromatography require sample derivatization, as does reverse phase liquid chromatography. In contrast, ion chromatography can separate the analytes directly, but requires a separate analytical method to quantify muramic acid. In this work we present a direct analysis of all these molecules using hydrophilic liquid interaction chromatography. Solvent composition, buffer strength, pH, flow rate, and column temperature were optimized. The method can separate these four compounds and the biopolymeric precursor molecule N-acetylglucosamine in a single run in under 8 min with equivalent resolution to the best previously reported separations that did not require derivatization prior to analysis. Detection of the analytes was performed by both tandem and time-of-flight mass spectrometry. The method was assessed for its quantitative capabilities through i) peak area assignment, ii) check standards with ratios of the target analytes likely to be present in real samples, iii) an injection internal standard, and iv) quantitative analysis of real soil hydrolysates by external calibration and standard addition approaches. Across their expected analytical ranges the response for each analyte was highly linear with good accuracy (〈25%) and precision (〈15%) over three orders of magnitude. Detection limits of 20 µg L〈sup〉−1〈/sup〉 were found for galactosamine and 5 µg L〈sup〉−1〈/sup〉 for the remainder of the analytes, comparable to the majority of other methods reported in the literature. Overall, this new approach can directly and rapidly quantify amino sugars recovered in environmental hydrolysates.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 3 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Julie Robinson, David Roush, Steven M. Cramer〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The present paper builds upon previous work on mAb domain contributions to multimodal (MM) chromatography by examining how pH can impact mAb surface properties and retention in these systems. Linear salt gradient experiments were carried out between pH 5–7 for several mAbs with different pI and surface hydrophobicities in four different MM CEX resins at two ligand densities. mAb retention showed an inverse, non-linear correlation with pH. Changing pH affected the elution order, creating unique windows of selectivity in each of the MM CEX resins. One mAb showed a pH-dependent spectrum of domain contributions, demonstrating that pH can be used to tune the relative importance of the (Fab)〈sub〉2〈/sub〉 and Fc domains for some mAbs in MM systems. Positive, negative, and hydrophobic patches were calculated between pH 5–7 for the mAbs. Visualizing these patches on the protein surface demonstrated that each mAb showed a unique distribution of surface charge and hydrophobicity that changed with pH. The sum of patch areas was tracked across this pH range to quantitatively understand how pH impacted these important surface properties. The quantitative analysis then was narrowed to consider only patches in the CDR loops, which were hypothesized to be an important interaction site for some mAbs in these systems. Interestingly, differences in the titration of CDR loop patches for each mAb were shown to be a result of Histidine titrations and patches in this region were qualitatively correlated with experimental trends including the observed elution order reversals. These results indicate that pH potentially can be employed as a lever for the strategic design of multimodal steps to create flow through, bind and elute, or weak partitioning operations with important implications for the design of integrated and/or continuous downstream purification processes. Furthermore, the ability to tune domain contributions in MM separations using pH creates intriguing possibilities for current downstream challenges such as the removal of product-related impurities, as well as the purification of bispecific mAbs.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 31 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Nancy Nazem Wanna, Karen Van Hoecke, Andrew Dobney, Mirela Vasile, Thomas Cardinaels, Frank Vanhaecke〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉High-pressure ion chromatography (HPIC) was coupled with sector field inductively coupled plasma-mass spectrometry (SF-ICP-MS) to separate plutonium (Pu), uranium (U), neodymium (Nd) and gadolinium (Gd) nuclides from isobaric nuclides and to quantify them with high sensitivity. In this study, mixed bed ion exchange columns CG5A and CS5A were used, from which Pu and U were eluted first using 1 M nitric acid. The lanthanides were then separated using a gradient of 0.1 - 0.15 M oxalic acid with the pH adjusted to 4.5. The HPIC-SF-ICP-MS method was validated using different sample matrices, i.e. spent nuclear fuel and soil. The method was found to be repeatable and gave rise to transient signals suitable for quantification of nuclide-specific concentrations using external calibration. In terms of accuracy, the HPIC-SF-ICP-MS measurement results were in good agreement with those obtained using thermal ionization mass spectrometry (TIMS). Finally, the method provides an improvement in sample throughput (≤ 60 minutes per sample) and reduces exposure of the operator to radiation compared to off-line gravitational chromatography followed by TIMS.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 31 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Ashin Taniguchi, Saki Tamura, Tohru Ikegami〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Silica particles with various pore sizes were modified with poly(acrylamide) via surface-initiated atom-transfer radical polymerization (SI-ATRP) under different reaction conditions. Twenty different columns were prepared and characterized according to a test method for hydrophilic interaction liquid chromatography (HILIC) columns. Hydrophilic retention by the SI-ATRP columns was much higher than that of poly(acrylamide) columns prepared via free-radical polymerization and many commercially available HILIC columns. The SI-ATRP columns displayed greater selectivity for –OH groups than any of the HILIC columns based on their α(U/2dU) values. SI-ATRP functionalization was used to increase the polymer chain density on the silica particles, which suggested a brush-type morphology, and improved hydrophilic selectivity. This indicated that hydrophilic retention and selectivity could be controlled by adjusting the morphology of the organic stationary phase. This stationary phase design strategy was validated experimentally by the effective separation of highly hydrophilic analytes. The findings of this study will greatly contribute to the creation of better separation media.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 27 February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Jianli Han, Qinghui Chen, Wanjun Jin, Meiyi Zou, Yu Lu, Yuxia Liu, Chengjian Wang, Zhongfu Wang, Linjuan Huang〈/p〉

Description: 〈p〉Publication date: Available online 27 February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Junmei Li, Jing An, Ye Jiang〈/p〉

Description: 〈p〉Publication date: Available online 28 February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Zhou Lu, Nan Fang, Zhongbei Zhang, Zhiguang Hou, Zhongbin Lu, Yueru Li〈/p〉

Description: 〈p〉Publication date: Available online 28 February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): A. Fromme, C. Fischer, D. Klump, G. Schembecker〈/p〉

Description: 〈p〉Publication date: Available online 26 February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Lixin Duan, Aimin Ma, Xianbin Meng, Guo-an Shen, Xiaoquan Qi〈/p〉

Description: 〈p〉Publication date: Available online 21 February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Fabrice Gritti, Janika Hochstrasser, Artur Svidrytski, Dzmitry Hlushkou, Ulrich Tallarek〈/p〉

Description: 〈p〉Publication date: Available online 20 February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Jessica Lin, Charlotte Tsang, Raymond Lieu, Kelly Zhang〈/p〉

Description: 〈p〉Publication date: Available online 21 February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Xiaoyan Liu, Hui Zhang, Mei Su, Yue Sun, Hongming Liu, Hengchang Zang, Lei Nie〈/p〉

Description: 〈p〉Publication date: Available online 18 February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Haijun Chen, Jianfeng Chen, Tao Tang, Hailu Chen, Luofeng Xie, Aihua Peng, Lijuan Chen, Guofu Yin〈/p〉

Description: 〈p〉Publication date: Available online 19 February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Xiaoqing Fu, Malgorzata Cebo, Tohru Ikegami, Michael Lämmerhofer〈/p〉

Description: 〈p〉Publication date: Available online 18 February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Sonia Schöneich, Derrick V. Gough, Timothy J. Trinklein, Robert E. Synovec〈/p〉

Description: 〈p〉Publication date: Available online 16 February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Gábor Tóth, Károly Vékey, Simon Sugár, Ilona Kovalszky, László Drahos, Lilla Turiák〈/p〉

Description: 〈p〉Publication date: Available online 14 February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): 〈/p〉

Description: 〈p〉Publication date: Available online 14 February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Chromatography A〈/p〉 〈p〉Author(s): Paweł Mateusz Nowak〈/p〉