An automatic on-line 2,2-diphenyl-1-picrylhydrazyl-high performance liquid chromatography method for high-throughput screening of antioxidants from natural products

Publication date: 27 October 2017 Source:Journal of Chromatography A, Volume 1521 Author(s): Yanzhen Lu, Nan Wu, Yingtong Fang, Nusrat Shaheen, Yun Wei Many natural products are rich in antioxidants which play an important ro…

Publication date: 27 October 2017
Source:Journal of Chromatography A, Volume 1521

Author(s): Yanzhen Lu, Nan Wu, Yingtong Fang, Nusrat Shaheen, Yun Wei

Many natural products are rich in antioxidants which play an important role in preventing or postponing a variety of diseases, such as cardiovascular and inflammatory disease, diabetes as well as breast cancer. In this paper, an automatic on-line 2,2-diphenyl-1-picrylhydrazyl-high performance liquid chromatography (DPPH-HPLC) method was established for antioxidants screening with nine standards including organic acids (4-hydroxyphenylacetic acid, p-coumaric acid, ferulic acid, and benzoic acid), alkaloids (coptisine and berberine), and flavonoids (quercitrin, astragalin, and quercetin). The optimal concentration of DPPH was determined, and six potential antioxidants including 4-hydroxyphenylacetic acid, p-coumaric acid, ferulic acid, quercitrin, astragalin, and quercetin, and three non-antioxidants including benzoic acid, coptisine, and berberine, were successfully screened out and validated by conventional DPPH radical scavenging activity assay. The established method has been applied to the crude samples of Saccharum officinarum rinds, Coptis chinensis powders, and Malus pumila leaves, consecutively. Two potential antioxidant compounds from Saccharum officinarum rinds and five potential antioxidant compounds from Malus pumila eaves were rapidly screened out. Then these seven potential antioxidants were purified and identified as p-coumaric acid, ferulic acid, phloridzin, isoquercitrin, quercetin-3-xyloside, quercetin-3-arabinoside, and quercetin-3-rhamnoside using countercurrent chromatography combined with mass spectrometry and their antioxidant activities were further evaluated by conventional DPPH radical scavenging assay. The activity result was in accordance with that of the established method. This established method is cheap and automatic, and could be used as an efficient tool for high-throughput antioxidant screening from various complex natural products.





Liquid chromatography – high resolution mass spectrometry-based metabolomic approach for the detection of Continuous Erythropoiesis Receptor Activator effects in horse doping control

Publication date: 27 October 2017
Source:Journal of Chromatography A, Volume 1521
Author(s): Céline Joré, Benoît Loup, Patrice Garcia, Anne-Christelle Paris, Marie-Agnès Popot, Michel Audran, Yves Bonnaire, Emmanuelle Varlet-Marie, Ludovic Bailly-Chouriberry
Erythropoiesis Stimulating Agents (ESAs) were developed for therapeutic purposes to stimulate red blood cell (RBC) production. Consequently, tissue oxygenation is enhanced as athlete’s endurance and ESAs misuse now benefits doping. Our hypothesis is that most of ESAs should have similar mechanisms and thus have the same effects on metabolism. Studying the metabolome variations could allow suspecting the use of any ESAs with a single method by targeting their effects. In this objective, a metabolomic study was carried out on 3 thoroughbred horses with a single administration of 4.2μg/kg of Mircera®, also called Continuous Erythropoiesis Receptor Activator (CERA). Blood and urine samples were collected from D-17 to D+74 and haematological parameters were followed throughout the study as plasmatic CERA concentration (ELISA). Urine and plasma metabolic fingerprints were recorded by Liquid Chromatography coupled to High Resolution Mass Spectrometry (LC-HRMS) in positive and negative mode. After preprocessing steps, normalized data were analyzed by multivariate statistics to build OPLS models. Hemoglobin concentration and hematocrit showed a significant increase after CERA administration unlike reticulocytes. CERA concentration showed a high intensity peak and then a slow decrease until becoming undetectable after D+31. Models built with multivariate statistics allow a discrimination between pre and post-administration plasma and urine samples until 74days after administration, i.e. 43days longer than ELISA method. By reducing and studying variables (ions), some potential candidate biomarkers were found.

Publication date: 27 October 2017
Source:Journal of Chromatography A, Volume 1521

Author(s): Céline Joré, Benoît Loup, Patrice Garcia, Anne-Christelle Paris, Marie-Agnès Popot, Michel Audran, Yves Bonnaire, Emmanuelle Varlet-Marie, Ludovic Bailly-Chouriberry

Erythropoiesis Stimulating Agents (ESAs) were developed for therapeutic purposes to stimulate red blood cell (RBC) production. Consequently, tissue oxygenation is enhanced as athlete's endurance and ESAs misuse now benefits doping. Our hypothesis is that most of ESAs should have similar mechanisms and thus have the same effects on metabolism. Studying the metabolome variations could allow suspecting the use of any ESAs with a single method by targeting their effects. In this objective, a metabolomic study was carried out on 3 thoroughbred horses with a single administration of 4.2μg/kg of Mircera®, also called Continuous Erythropoiesis Receptor Activator (CERA). Blood and urine samples were collected from D-17 to D+74 and haematological parameters were followed throughout the study as plasmatic CERA concentration (ELISA). Urine and plasma metabolic fingerprints were recorded by Liquid Chromatography coupled to High Resolution Mass Spectrometry (LC-HRMS) in positive and negative mode. After preprocessing steps, normalized data were analyzed by multivariate statistics to build OPLS models. Hemoglobin concentration and hematocrit showed a significant increase after CERA administration unlike reticulocytes. CERA concentration showed a high intensity peak and then a slow decrease until becoming undetectable after D+31. Models built with multivariate statistics allow a discrimination between pre and post-administration plasma and urine samples until 74days after administration, i.e. 43days longer than ELISA method. By reducing and studying variables (ions), some potential candidate biomarkers were found.





Additional band broadening of peptides in the first size-exclusion chromatographic dimension of an automated stop-flow two-dimensional high performance liquid chromatography

Publication date: 27 October 2017
Source:Journal of Chromatography A, Volume 1521
Author(s): Jucai Xu, Dongxiao Sun-Waterhouse, Chaoying Qiu, Mouming Zhao, Baoguo Sun, Lianzhu Lin, Guowan Su
The need to improve the peak capacity of liquid chromatography motivates the development of two-dimensional analysis systems. This paper presented a fully automated stop-flow two-dimensional liquid chromatography system with size exclusion chromatography followed by reversed phase liquid chromatography (SEC×RPLC) to efficiently separate peptides. The effects of different stop-flow operational parameters (stop-flow time, peak parking position, number of stop-flow periods and column temperature) on band broadening in the first dimension (1st D) SEC column were quantitatively evaluated by using commercial small proteins and peptides. Results showed that the effects of peak parking position and the number of stop-flow periods on band broadening were relatively small. Unlike stop-flow analysis of large molecules with a long running time, additional band broadening was evidently observed for small molecule analytes due to the relatively high effective diffusion coefficient (Deff). Therefore, shorter analysis time and lower 1st D column temperature were suggested for analyzing small molecules. The stop-flow two-dimensional liquid chromatography (2D-LC) system was further tested on peanut peptides and an evidently improved resolution was observed for both stop-flow heart-cutting and comprehensive 2D-LC analysis (in spite of additional band broadening in SEC). The stop-flow SEC×RPLC, especially heart-cutting analysis with shorter analysis time and higher 1st D resolution for selected fractions, offers a promising approach for efficient analysis of complex samples.

Publication date: 27 October 2017
Source:Journal of Chromatography A, Volume 1521

Author(s): Jucai Xu, Dongxiao Sun-Waterhouse, Chaoying Qiu, Mouming Zhao, Baoguo Sun, Lianzhu Lin, Guowan Su

The need to improve the peak capacity of liquid chromatography motivates the development of two-dimensional analysis systems. This paper presented a fully automated stop-flow two-dimensional liquid chromatography system with size exclusion chromatography followed by reversed phase liquid chromatography (SEC×RPLC) to efficiently separate peptides. The effects of different stop-flow operational parameters (stop-flow time, peak parking position, number of stop-flow periods and column temperature) on band broadening in the first dimension (1st D) SEC column were quantitatively evaluated by using commercial small proteins and peptides. Results showed that the effects of peak parking position and the number of stop-flow periods on band broadening were relatively small. Unlike stop-flow analysis of large molecules with a long running time, additional band broadening was evidently observed for small molecule analytes due to the relatively high effective diffusion coefficient (Deff ). Therefore, shorter analysis time and lower 1st D column temperature were suggested for analyzing small molecules. The stop-flow two-dimensional liquid chromatography (2D-LC) system was further tested on peanut peptides and an evidently improved resolution was observed for both stop-flow heart-cutting and comprehensive 2D-LC analysis (in spite of additional band broadening in SEC). The stop-flow SEC×RPLC, especially heart-cutting analysis with shorter analysis time and higher 1st D resolution for selected fractions, offers a promising approach for efficient analysis of complex samples.





Influence of mixed electrolytes and pH on adsorption of bovine serum albumin in hydrophobic interaction chromatography

Publication date: 27 October 2017
Source:Journal of Chromatography A, Volume 1521
Author(s): Eva Hackemann, Hans Hasse
Using salt mixtures instead of single salts can be beneficial for hydrophobic interaction chromatography (HIC). The effect of electrolytes on the adsorption of proteins, however, depends on the pH. Little is known on that dependence for mixed electrolytes. Therefore, the effect of the pH on protein adsorption from aqueous solutions containing mixed salts is systematically studied in the present work for a model system: the adsorption of bovine serum albumin (BSA) on the mildly hydrophobic resin Toyopearl PPG-600M. The pH is adjusted to 4.0, 4.7 or 7.0 using 25mM sodium phosphate or sodium citrate buffer. Binary and ternary salt mixtures of sodium chloride, ammonium chloride, sodium sulfate and ammonium sulfate as well as the pure salts are used at overall ionic strengths between 1500 and 4200mM. The temperature is always 25°C. The influence of the mixed electrolytes on the adsorption behavior of BSA changes completely with varying pH. Positive as well as negative cooperative effects of the mixed electrolytes are observed. The results are analyzed using a mathematical model which was recently introduced by our group. In that model the influence of the electrolytes is described by a Taylor series expansion in the individual ion molarities. After suitable parametrization using a subset of the data determined in the present work, the model successfully predicts the influence of mixed electrolytes on the protein adsorption. Furthermore, results for BSA from the present study are compared to literature data for lysozyme, which are available for the same adsorbent, temperature and salts. By calculating the ratio of the loading of the adsorbent for both proteins particularly favorable separation conditions can be selected. Hence, a model-based optimization of solvents for protein separation is possible.

Publication date: 27 October 2017
Source:Journal of Chromatography A, Volume 1521

Author(s): Eva Hackemann, Hans Hasse

Using salt mixtures instead of single salts can be beneficial for hydrophobic interaction chromatography (HIC). The effect of electrolytes on the adsorption of proteins, however, depends on the pH. Little is known on that dependence for mixed electrolytes. Therefore, the effect of the pH on protein adsorption from aqueous solutions containing mixed salts is systematically studied in the present work for a model system: the adsorption of bovine serum albumin (BSA) on the mildly hydrophobic resin Toyopearl PPG-600M. The pH is adjusted to 4.0, 4.7 or 7.0 using 25mM sodium phosphate or sodium citrate buffer. Binary and ternary salt mixtures of sodium chloride, ammonium chloride, sodium sulfate and ammonium sulfate as well as the pure salts are used at overall ionic strengths between 1500 and 4200mM. The temperature is always 25°C. The influence of the mixed electrolytes on the adsorption behavior of BSA changes completely with varying pH. Positive as well as negative cooperative effects of the mixed electrolytes are observed. The results are analyzed using a mathematical model which was recently introduced by our group. In that model the influence of the electrolytes is described by a Taylor series expansion in the individual ion molarities. After suitable parametrization using a subset of the data determined in the present work, the model successfully predicts the influence of mixed electrolytes on the protein adsorption. Furthermore, results for BSA from the present study are compared to literature data for lysozyme, which are available for the same adsorbent, temperature and salts. By calculating the ratio of the loading of the adsorbent for both proteins particularly favorable separation conditions can be selected. Hence, a model-based optimization of solvents for protein separation is possible.





High-resolution two-dimensional liquid chromatography analysis of key linker drug intermediate used in antibody drug conjugates

Publication date: 27 October 2017
Source:Journal of Chromatography A, Volume 1521
Author(s): C.J. Venkatramani, Shu Rong Huang, Mohammad Al-Sayah, Ila Patel, Larry Wigman
In this manuscript, the application of high-resolution sampling (HRS) two-dimensional liquid chromatography (2D-LC) in the detailed analysis of key linker drug intermediate is presented. Using HRS, selected regions of the primary column eluent were transferred to a secondary column with fidelity enabling qualitative and quantitative analysis of linker drugs. The primary column purity of linker drug intermediate ranged from 88.9% to 94.5% and the secondary column purity ranged from 99.6% to 99.9%, showing lot-to-lot variability, significant differences between the three lots, and substantiating the synthetic and analytical challenges of ADCs. Over 15 impurities co-eluting with the linker drug intermediate in the primary dimension were resolved in the secondary dimension. The concentrations of most of these impurities were over three orders of magnitude lower than the linker drug. Effective peak focusing and high-speed secondary column analysis resulted in sharp peaks in the secondary dimension, improving the signal-to-noise ratios. The sensitivity of 2D-LC separation was over five fold better than conventional HPLC separation. The limit of quantitation (LOQ) was less than 0.01%. Many peaks originating from primary dimension were resolved into multiple components in the complementary secondary dimension, demonstrating the complexity of these samples. The 2D-LC was highly reproducible, showing good precision between runs with%RSD of peak areas less than 0.1 for the main component. The absolute difference in the peak areas of impurities less than 0.1% were within ±0.01% and for impurities in the range of 0.1%–0.3%, the absolute difference were ±0.02%, which are comparable to 1D-LC. The overall purity of the linker drug intermediate was determined from the product of primary and secondary column purity (HPLC Purity=%peak area of main component in the primary dimension×%peak area of main component in the secondary dimension). Additionally, the 2D-LC separation enables the determination of potential impurities that could impact the downstream process, like ADCs stability, efficacy and patient safety. Peak capacity of this magnitude, sensitivity and reproducibility of 2D-LC for resolving structurally similar impurities co-eluting with the main component has not been demonstrated to date. This application clearly demonstrates the power of 2D-LC in detailed analysis of structurally similar, co-eluting impurities from key linker drug intermediate used in ADCs that is impossible to achieve by conventional 1D-LC.

Publication date: 27 October 2017
Source:Journal of Chromatography A, Volume 1521

Author(s): C.J. Venkatramani, Shu Rong Huang, Mohammad Al-Sayah, Ila Patel, Larry Wigman

In this manuscript, the application of high-resolution sampling (HRS) two-dimensional liquid chromatography (2D-LC) in the detailed analysis of key linker drug intermediate is presented. Using HRS, selected regions of the primary column eluent were transferred to a secondary column with fidelity enabling qualitative and quantitative analysis of linker drugs. The primary column purity of linker drug intermediate ranged from 88.9% to 94.5% and the secondary column purity ranged from 99.6% to 99.9%, showing lot-to-lot variability, significant differences between the three lots, and substantiating the synthetic and analytical challenges of ADCs. Over 15 impurities co-eluting with the linker drug intermediate in the primary dimension were resolved in the secondary dimension. The concentrations of most of these impurities were over three orders of magnitude lower than the linker drug. Effective peak focusing and high-speed secondary column analysis resulted in sharp peaks in the secondary dimension, improving the signal-to-noise ratios. The sensitivity of 2D-LC separation was over five fold better than conventional HPLC separation. The limit of quantitation (LOQ) was less than 0.01%. Many peaks originating from primary dimension were resolved into multiple components in the complementary secondary dimension, demonstrating the complexity of these samples. The 2D-LC was highly reproducible, showing good precision between runs with%RSD of peak areas less than 0.1 for the main component. The absolute difference in the peak areas of impurities less than 0.1% were within ±0.01% and for impurities in the range of 0.1%–0.3%, the absolute difference were ±0.02%, which are comparable to 1D-LC. The overall purity of the linker drug intermediate was determined from the product of primary and secondary column purity (HPLC Purity=%peak area of main component in the primary dimension×%peak area of main component in the secondary dimension). Additionally, the 2D-LC separation enables the determination of potential impurities that could impact the downstream process, like ADCs stability, efficacy and patient safety. Peak capacity of this magnitude, sensitivity and reproducibility of 2D-LC for resolving structurally similar impurities co-eluting with the main component has not been demonstrated to date. This application clearly demonstrates the power of 2D-LC in detailed analysis of structurally similar, co-eluting impurities from key linker drug intermediate used in ADCs that is impossible to achieve by conventional 1D-LC.





Synthesis and evaluation of pseudopeptide chiral stationary phases for enantioselective resolution

Publication date: 27 October 2017
Source:Journal of Chromatography A, Volume 1521
Author(s): Huifang Shen, Ganhong Du, Keyuan Liu, Long Ye, Shoulei Xie, Liming Jiang
Poly(2-oxazoline)s are regarded as bioinspired polymers due to their structural relation to polypeptides. In this work, a new kind of poly(2-oxazoline)s containing dipeptide segments in the side chains was synthesized through a bottom-up protocol, which involves ring-opening copolymerization of 2-(N-Boc-l-2-pyrrolidinyl)-2-oxazoline (PyOXBoc) with 2-(3-butenyl)-2-oxazoline (BuOX) followed by deprotection and amide coupling with N-protected L-proline. The resulting vinyl-functionalized polymers were subsequently immobilized onto mercaptopropylated silica bead matrices by means of thio-click chemistry and their potential as the chiral stationary phase (CSP) for high-performance liquid chromatography was preliminarily evaluated with a series of structurally different racemates. The results showed that this class of pseudopeptide CSPs is particularly adapted to the enantiomeric separation of 1,1′-bi-2-naphthol and acyloin compounds (such as benzoin) under normal-phase conditions. Moreover, an increase in the length of polymer main chains is beneficial to the enhancement of both enantioselectivity and resolution ability. The chiral discrimination of analytes by the polymeric selectors stems primarily from hydrogen bonding and π-π interactions as well as steric hindrance.

Publication date: 27 October 2017
Source:Journal of Chromatography A, Volume 1521

Author(s): Huifang Shen, Ganhong Du, Keyuan Liu, Long Ye, Shoulei Xie, Liming Jiang

Poly(2-oxazoline)s are regarded as bioinspired polymers due to their structural relation to polypeptides. In this work, a new kind of poly(2-oxazoline)s containing dipeptide segments in the side chains was synthesized through a bottom-up protocol, which involves ring-opening copolymerization of 2-(N-Boc-l-2-pyrrolidinyl)-2-oxazoline (PyOXBoc) with 2-(3-butenyl)-2-oxazoline (BuOX) followed by deprotection and amide coupling with N-protected L-proline. The resulting vinyl-functionalized polymers were subsequently immobilized onto mercaptopropylated silica bead matrices by means of thio-click chemistry and their potential as the chiral stationary phase (CSP) for high-performance liquid chromatography was preliminarily evaluated with a series of structurally different racemates. The results showed that this class of pseudopeptide CSPs is particularly adapted to the enantiomeric separation of 1,1′-bi-2-naphthol and acyloin compounds (such as benzoin) under normal-phase conditions. Moreover, an increase in the length of polymer main chains is beneficial to the enhancement of both enantioselectivity and resolution ability. The chiral discrimination of analytes by the polymeric selectors stems primarily from hydrogen bonding and π-π interactions as well as steric hindrance.





Optimized purification of a fusion protein by reversed-phase high performance liquid chromatography informed by the linear solvent strength model

Publication date: 27 October 2017 Source:Journal of Chromatography A, Volume 1521 Author(s): Isaac B. Falconer, Colin T. Mant, C. James McKnight, Liliya Vugmeyster, Robert Hodges Fusion protein systems are commonly used for e…

Publication date: 27 October 2017
Source:Journal of Chromatography A, Volume 1521

Author(s): Isaac B. Falconer, Colin T. Mant, C. James McKnight, Liliya Vugmeyster, Robert Hodges

Fusion protein systems are commonly used for expression of small proteins and peptides. An important criterion for a fusion protein system to be useful is the ability to separate the protein of interest from the tag. Additionally, because no protease cleaves fusion proteins with 100% efficiency, the ability to separate the desired peptide from any remaining uncleaved protein is also necessary. This is likely to be the more difficult task as at least a portion of the sequence of the fusion protein is identical to that of the protein of interest. When a high level of purity is required, gradient elution reversed-phase HPLC is frequently used as a final purification step. Shallow gradients are often advantageous for maximizing both the purity and yield of the final product; however, the relationship between relative retention times at shallow gradients and those at steeper gradients typically used for analytical HPLC are not always straightforward. In this work, we report reversed-phase HPLC results for the fusion protein system consisting of the N-terminal domain of ribosomal protein L9 (NTL9) and the 36-residue villin headpiece subdomain (HP36) linked by a recognition sequence for the protease factor Xa. This system represents an excellent example of the difficulties in purification that may arise from this unexpected elution behavior at shallow gradients. Additionally, we report on the sensitivity of this elution behavior to the concentration of the additive trifluoroacetic acid in the mobile phase and present optimized conditions for separating HP36 from the full fusion protein by reversed-phase HPLC using a shallow gradient. Finally, we suggest that these findings are relevant to the purification of other fusion protein systems, for which similar problems may arise, and support this suggestion using insights from the linear solvent strength model of gradient elution liquid chromatography.





Facile preparation of molybdenum (VI) oxide – Modified graphene oxide nanocomposite for specific enrichment of phosphopeptides

Publication date: 27 October 2017
Source:Journal of Chromatography A, Volume 1521
Author(s): Haofan Sun, Quanqing Zhang, Lei Zhang, Weibing Zhang, Lingyi Zhang
To promote the development of phosphoproteome analysis in highly selective efficient tracing phosphorylated proteins or peptides, views of researches should not confined with intrinsic materials and their modification. New materials are supposed to be explored for phosphoproteome analysis. In this work, we first introduced Molybdenum (VI) oxide (MoO3) into phosphoproteome, loading on the graphene oxide (GO) nanosheets forming MoO3/GO nanocomposites by a simple two-step strategy. The GO nanosheets offered MoO3 a perfect stable platform for separation and concentration and MoO3 exhibited wonderful property in enriching phosphopeptides with highly selectivity and sensitivity on GO nanosheets. Specifically, the as-synthesized MoO3/GO nanocomposites exhibited excellent specificity (β-casein: BSA=1:1000), high detection sensitivity (1 fmol/mL) and well recovery (91.13%) in enriching phosphopeptides by metal oxide affinity chromatography (MOAC). Moreover, the as-synthesized MoO3/GO nanocomposites provided effective enrichment of phosphopeptides from nonfat milk (a total of twelve phosphopeptides signals) and human serum (a total of four endogenous phosphopeptides signals), displaying great biological compatibility, which demonstrated that the MoO3/GO nanocomposites is a promising candidate in selectively identifying and determining low-abundance phosphorylated peptides in biological sample.

Publication date: 27 October 2017
Source:Journal of Chromatography A, Volume 1521

Author(s): Haofan Sun, Quanqing Zhang, Lei Zhang, Weibing Zhang, Lingyi Zhang

To promote the development of phosphoproteome analysis in highly selective efficient tracing phosphorylated proteins or peptides, views of researches should not confined with intrinsic materials and their modification. New materials are supposed to be explored for phosphoproteome analysis. In this work, we first introduced Molybdenum (VI) oxide (MoO3) into phosphoproteome, loading on the graphene oxide (GO) nanosheets forming MoO3/GO nanocomposites by a simple two-step strategy. The GO nanosheets offered MoO3 a perfect stable platform for separation and concentration and MoO3 exhibited wonderful property in enriching phosphopeptides with highly selectivity and sensitivity on GO nanosheets. Specifically, the as-synthesized MoO3/GO nanocomposites exhibited excellent specificity (β-casein: BSA=1:1000), high detection sensitivity (1 fmol/mL) and well recovery (91.13%) in enriching phosphopeptides by metal oxide affinity chromatography (MOAC). Moreover, the as-synthesized MoO3/GO nanocomposites provided effective enrichment of phosphopeptides from nonfat milk (a total of twelve phosphopeptides signals) and human serum (a total of four endogenous phosphopeptides signals), displaying great biological compatibility, which demonstrated that the MoO3/GO nanocomposites is a promising candidate in selectively identifying and determining low-abundance phosphorylated peptides in biological sample.





Electrospun nanofibers-based online micro-solid phase extraction for the determination of monohydroxy polycyclic aromatic hydrocarbons in human urine

Publication date: 27 October 2017
Source:Journal of Chromatography A, Volume 1521
Author(s): Huifang Zhang, Hui Xu
In this article, silver nanoparticles (AgNPs) modified nanofibers that represent a novel kind of packing materials for micro-solid phase extraction (μ-SPE) is reported for the first time. The composite material was fabricated through in-situ formation of AgNPs on the polydopamine (PDA) coated polystyrene electrospun fibers (PS@PDA-Ag). The nanofibers displayed desirable hydrophilicity, large surface area, high porosity, good extraction ability and certain capacity to resist matrix interference. A μ-SPE combined with liquid chromatography-mass spectrometry (LC–MS) method was developed for the online determination of three monohydroxy polycyclic aromatic hydrocarbons (OH-PAHs) metabolites in human urine. Under the optimal conditions, good linearity (0.02–5ngmL−1) was acquired with the correlation coefficients (R2) being larger than 0.9962. Low limits of detection (0.007–0.032ngmL−1) expressed the satisfactory sensitivity of the method. Moreover, the intraday relative standard deviation values lower than 9.7% and the recoveries among the range of 71–116% were obtained. In general, the online μ-SPE-LC–MS method had the features of simplicity, rapidity, sensitivity and automation, and it was expected to become a promising approach for the online analysis of trace OH-PAHs in complex biological samples.

Publication date: 27 October 2017
Source:Journal of Chromatography A, Volume 1521

Author(s): Huifang Zhang, Hui Xu

In this article, silver nanoparticles (AgNPs) modified nanofibers that represent a novel kind of packing materials for micro-solid phase extraction (μ-SPE) is reported for the first time. The composite material was fabricated through in-situ formation of AgNPs on the polydopamine (PDA) coated polystyrene electrospun fibers (PS@PDA-Ag). The nanofibers displayed desirable hydrophilicity, large surface area, high porosity, good extraction ability and certain capacity to resist matrix interference. A μ-SPE combined with liquid chromatography-mass spectrometry (LC–MS) method was developed for the online determination of three monohydroxy polycyclic aromatic hydrocarbons (OH-PAHs) metabolites in human urine. Under the optimal conditions, good linearity (0.02–5ngmL−1) was acquired with the correlation coefficients (R2) being larger than 0.9962. Low limits of detection (0.007–0.032ngmL−1) expressed the satisfactory sensitivity of the method. Moreover, the intraday relative standard deviation values lower than 9.7% and the recoveries among the range of 71–116% were obtained. In general, the online μ-SPE-LC–MS method had the features of simplicity, rapidity, sensitivity and automation, and it was expected to become a promising approach for the online analysis of trace OH-PAHs in complex biological samples.





Facile and green fabrication of cation exchange membrane adsorber with unprecedented adsorption capacity for protein purification

Publication date: 27 October 2017 Source:Journal of Chromatography A, Volume 1521 Author(s): M. Kamran Khan, Jianquan Luo, Rashid Khan, Jinxin Fan, Yinhua Wan Fabricating membrane adsorbers with high adsorption capacity and a…

Publication date: 27 October 2017
Source:Journal of Chromatography A, Volume 1521

Author(s): M. Kamran Khan, Jianquan Luo, Rashid Khan, Jinxin Fan, Yinhua Wan

Fabricating membrane adsorbers with high adsorption capacity and appreciable throughput for the separation and purification of protein products is challenging in biomedical and pharmaceutical industries. Herein, we report the synthesis of a novel membrane adsorber by functionalizing a nylon microfiltration membrane with alginate dialdehyde (ADA) followed by sulphonic addition, without any solvent usage, and its successful application in the purification of lysozyme. Taking advantage of abundant dual cation exchange (CEX) groups on sulphonic-ADA (S-ADA) ligands, this novel S-ADA-nylon membrane adsorber showed an unprecedented static binding capicity of 286mg/mL for lysozyme adsorption. Meanwhile, the prepared membrane adsorber could be easily regenerated (complete protein elution) under mild conditions and be reused at least for five times. Featured with a unique selectivity, the S-ADA-nylon membrane also captured lysozyme from chicken egg white solution with a high purity (100%) and a high recovery of 98%. The purified lysozyme showed similar specific activity as commercial product. The present work provides a facile, green and low-cost approach for the preparation of high-performance membrane adsorbers, which has a great potential in protein production.





Automatic single-step quick, easy, cheap, effective, rugged and safe sample preparation devices for analysis of pesticide residues in foods

Publication date: 27 October 2017
Source:Journal of Chromatography A, Volume 1521
Author(s): Jishi Wang, Zeying He, Lu Wang, Yaping Xu, Yi Peng, Xiaowei Liu
In this research, the manual two-step QuEChERS approach has been streamlined and automated into a one-step method using a cleanup tube fitted within an extraction tube. A novel automatic QuEChERS combination have been developed to simplify the QuEChERS procedures and improve sample preparation efficiency. This combination integrates QuEChERS procedures into a single run via the use of a vortex vibration-centrifuge device and a centrifuge filtration tube. To validate the efficiency of our automatic QuEChERS device, 270 pesticides were analyzed in plant origined foods including celery, tomatoes, leeks, eggplants, grapes, corn, green tea, and soybean oil using this automatic platform. The results were then compared with those obtained using the manual QuEChERS method. Different parameters were validated and compared including recovery, linearity, repeatability and limits of quantification (LOQ). Satisfactory results, comparable to results obtained using the manual QuEChERS method were obtained. The average recoveries ranged between 70% and 120% for most pesticides with associated relative standard deviations (RSDs) <20% (n=5) indicating satisfactory accuracy and repeatability. An LOQ of 2μg/kg was obtained for most pesticides present in celery and corn matrices, and the correlation coefficients (r2) were >0.990 within a linearity range of 2–500μg/kg. Compared to manual QuEChERS, this novel automatic QuEChERS device and combination could significantly improve the sample preparation efficiency for the multiresidue analysis of pesticides.

Publication date: 27 October 2017
Source:Journal of Chromatography A, Volume 1521

Author(s): Jishi Wang, Zeying He, Lu Wang, Yaping Xu, Yi Peng, Xiaowei Liu

In this research, the manual two-step QuEChERS approach has been streamlined and automated into a one-step method using a cleanup tube fitted within an extraction tube. A novel automatic QuEChERS combination have been developed to simplify the QuEChERS procedures and improve sample preparation efficiency. This combination integrates QuEChERS procedures into a single run via the use of a vortex vibration-centrifuge device and a centrifuge filtration tube. To validate the efficiency of our automatic QuEChERS device, 270 pesticides were analyzed in plant origined foods including celery, tomatoes, leeks, eggplants, grapes, corn, green tea, and soybean oil using this automatic platform. The results were then compared with those obtained using the manual QuEChERS method. Different parameters were validated and compared including recovery, linearity, repeatability and limits of quantification (LOQ). Satisfactory results, comparable to results obtained using the manual QuEChERS method were obtained. The average recoveries ranged between 70% and 120% for most pesticides with associated relative standard deviations (RSDs) <20% (n=5) indicating satisfactory accuracy and repeatability. An LOQ of 2μg/kg was obtained for most pesticides present in celery and corn matrices, and the correlation coefficients (r2) were >0.990 within a linearity range of 2–500μg/kg. Compared to manual QuEChERS, this novel automatic QuEChERS device and combination could significantly improve the sample preparation efficiency for the multiresidue analysis of pesticides.





Preparation of a reversed-phase/anion-exchange mixed-mode spherical sorbent by Pickering emulsion polymerization for highly selective solid-phase extraction of acidic pharmaceuticals from wastewater

Publication date: 27 October 2017
Source:Journal of Chromatography A, Volume 1521
Author(s): Chaonan Huang, Yun Li, Jiajia Yang, Junyu Peng, Jing Jin, Dhanjai, Jincheng Wang, Jiping Chen
The present work represents a simple and effective preparation of a novel mixed-mode anion-exchange (MAX) sorbent based on porous poly[2-(diethylamino)ethyl methacrylate-divinylbenzene] (poly(DEAEMA-DVB)) spherical particles synthesized by one-step Pickering emulsion polymerization. The poly(DEAEMA-DVB) particles were quaternized with 1,4-butanediol diglycidyl ether (BDDE) followed by triethylamine (TEA) via epoxy-amine reaction to offer strong anion exchange properties. The synthesized MAX sorbent was characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy, nitrogen adsorption-desorption measurements and elemental analysis. The MAX sorbent possessed regular spherical shape and narrow diameter distribution (15–35μm), a high IEC of 0.54meq/g, with carbon and nitrogen contents of 80.3% and 1.62%, respectively. Compared to poly(DEAEMA-DVB), the MAX sorbent exhibited decreased SBET (390.5 vs. 515.3m2g−1), pore volume (0.74 vs. 0.85cm3g−1) and pore size (16.8 vs. 17.3nm). Moreover, changes of N content for producing the MAX sorbent reveal a successful two-step quaternization, which can be highly related to such a high IEC. Finally, the MAX sorbent was successfully evaluated for selective isolation and purification of some selected acidic pharmaceuticals (ketoprofen, KEP; naproxen, NAP; and ibuprofen, IBP) from neutral (hydrocortisone, HYC), basic (carbamazepine, CAZ; amitriptyline, AMT) pharmaceuticals and other interferences in water samples using solid phase extraction (SPE). An efficient analytical method based on the MAX-based mixed-mode SPE coupled with HPLC-UV was developed for highly selective extraction and cleanup of acidic KEP, NAP and IBP in spiked wastewater samples. The developed method exhibited good sensitivity (0.009–0.085μgL−1 limit of detection), satisfactory recoveries (82.1%–105.5%) and repeatabilities (relative standard deviation < 7.9%, n=3).

Publication date: 27 October 2017
Source:Journal of Chromatography A, Volume 1521

Author(s): Chaonan Huang, Yun Li, Jiajia Yang, Junyu Peng, Jing Jin, Dhanjai, Jincheng Wang, Jiping Chen

The present work represents a simple and effective preparation of a novel mixed-mode anion-exchange (MAX) sorbent based on porous poly[2-(diethylamino)ethyl methacrylate-divinylbenzene] (poly(DEAEMA-DVB)) spherical particles synthesized by one-step Pickering emulsion polymerization. The poly(DEAEMA-DVB) particles were quaternized with 1,4-butanediol diglycidyl ether (BDDE) followed by triethylamine (TEA) via epoxy-amine reaction to offer strong anion exchange properties. The synthesized MAX sorbent was characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy, nitrogen adsorption-desorption measurements and elemental analysis. The MAX sorbent possessed regular spherical shape and narrow diameter distribution (15–35μm), a high IEC of 0.54meq/g, with carbon and nitrogen contents of 80.3% and 1.62%, respectively. Compared to poly(DEAEMA-DVB), the MAX sorbent exhibited decreased SBET (390.5 vs. 515.3m2 g−1), pore volume (0.74 vs. 0.85cm3 g−1) and pore size (16.8 vs. 17.3nm). Moreover, changes of N content for producing the MAX sorbent reveal a successful two-step quaternization, which can be highly related to such a high IEC. Finally, the MAX sorbent was successfully evaluated for selective isolation and purification of some selected acidic pharmaceuticals (ketoprofen, KEP; naproxen, NAP; and ibuprofen, IBP) from neutral (hydrocortisone, HYC), basic (carbamazepine, CAZ; amitriptyline, AMT) pharmaceuticals and other interferences in water samples using solid phase extraction (SPE). An efficient analytical method based on the MAX-based mixed-mode SPE coupled with HPLC-UV was developed for highly selective extraction and cleanup of acidic KEP, NAP and IBP in spiked wastewater samples. The developed method exhibited good sensitivity (0.009–0.085μgL−1 limit of detection), satisfactory recoveries (82.1%–105.5%) and repeatabilities (relative standard deviation < 7.9%, n=3).





Rapid quantitative detection of glucose content in glucose injection by reaction headspace gas chromatography

Publication date: 20 October 2017 Source:Journal of Chromatography A, Volume 1520 Author(s): Wei-Qi Xie, Yi-Xian Gong, Kong-Xian Yu This work investigates an automated technique for rapid detecting the glucose content in glucose …

Publication date: 20 October 2017
Source:Journal of Chromatography A, Volume 1520

Author(s): Wei-Qi Xie, Yi-Xian Gong, Kong-Xian Yu

This work investigates an automated technique for rapid detecting the glucose content in glucose injection by reaction headspace gas chromatography (HS-GC). This method is based on the oxidation reaction of glucose in glucose injection with potassium dichromate. The carbon dioxide (CO2) formed from the oxidation reaction can be quantitatively detected by GC. The results show that the relative standard deviation (RSD) of the present method was within 2.91%, and the measured glucose contents in glucose injection closely match those quantified by the reference method (relative differences <6.45%). The new HS-GC technique is rapid, practical and can be used to the batch detection of the glucose content in glucose injection related applications.





Headspace solid-phase microextraction coupled to comprehensive two-dimensional gas chromatography–time-of-flight mass spectrometry for the analysis of aerosol from tobacco heating product

Publication date: 20 October 2017
Source:Journal of Chromatography A, Volume 1520
Author(s): Benjamin Savareear, Radoslaw Lizak, Michał Brokl, Chris Wright, Chuan Liu, Jean-Francois Focant
A method involving headspace solid-phase microextraction (HS-SPME) and comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC-TOFMS) was developed and optimised to elucidate the volatile composition of the particulate phase fraction of aerosol produced by tobacco heating products (THPs). Three SPME fiber types were studied in terms of extraction capacity and precision measurements. Divinylbenzene polydimethylsiloxane appeared as the most efficient coating for these measurements. A central composite design of experiment was utilised for the optimization of the extraction conditions. Qualitative and semi-quantitative analysis of the headspace above THP aerosol condensate was carried out using optimised extraction conditions. Semi-quantitative analyses of detected constituents were performed by assuming that their relative response factors to the closest internal standard (itR) were equal to 1. Using deconvoluted mass spectral data (library similarity and reverse match >750) and linear retention indices (match window of ±15 index units), 205 peaks were assigned to individual compounds, 82 of which (including 43 substances previously reported to be present in tobacco) have not been reported previously in tobacco aerosol. The major volatile fraction of the headspace contained ketones, alcohols, aldehydes, alicyclic hydrocarbons alkenes, and alkanes. The method was further applied to compare the volatiles from the particulate phase of aerosol composition of THP with that of reference cigarette smoke and showed that the THP produced a less complex chemical mixture. This new method showed good efficiency and precision for the peak areas and peak numbers from the volatile fraction of aerosol particulate phase for both THP and reference cigarettes.

Publication date: 20 October 2017
Source:Journal of Chromatography A, Volume 1520

Author(s): Benjamin Savareear, Radoslaw Lizak, Michał Brokl, Chris Wright, Chuan Liu, Jean-Francois Focant

A method involving headspace solid-phase microextraction (HS-SPME) and comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC-TOFMS) was developed and optimised to elucidate the volatile composition of the particulate phase fraction of aerosol produced by tobacco heating products (THPs). Three SPME fiber types were studied in terms of extraction capacity and precision measurements. Divinylbenzene polydimethylsiloxane appeared as the most efficient coating for these measurements. A central composite design of experiment was utilised for the optimization of the extraction conditions. Qualitative and semi-quantitative analysis of the headspace above THP aerosol condensate was carried out using optimised extraction conditions. Semi-quantitative analyses of detected constituents were performed by assuming that their relative response factors to the closest internal standard (itR) were equal to 1. Using deconvoluted mass spectral data (library similarity and reverse match >750) and linear retention indices (match window of ±15 index units), 205 peaks were assigned to individual compounds, 82 of which (including 43 substances previously reported to be present in tobacco) have not been reported previously in tobacco aerosol. The major volatile fraction of the headspace contained ketones, alcohols, aldehydes, alicyclic hydrocarbons alkenes, and alkanes. The method was further applied to compare the volatiles from the particulate phase of aerosol composition of THP with that of reference cigarette smoke and showed that the THP produced a less complex chemical mixture. This new method showed good efficiency and precision for the peak areas and peak numbers from the volatile fraction of aerosol particulate phase for both THP and reference cigarettes.





Enantiomeric separation of some chiral analytes using amylose 3,5-dimethylphenylcarbamate covalently immobilized on silica by nano-liquid chromatography and capillary electrochromatography

Publication date: 20 October 2017
Source:Journal of Chromatography A, Volume 1520
Author(s): Giovanni D’Orazio, Chiara Fanali, Marina Karchkhadze, Bezhan Chankvetadze, Salvatore Fanali
A new experimental chiral stationary phase containing amylose 3,5-dimethylphenylcarbamate immobilized onto silica gel (i-ADMPC) was packed in 100μm I.D. fused silica capillary and used for the chiral separation of eight selected flavanone derivatives in polar organic mobile phase by using different miniaturized techniques, such as nano-liquid chromatography (nano-LC), capillary electrochromatography (CEC) and pressure-assisted CEC (pCEC). A comparative study of different elution modes in terms of chromatographic efficiency, analysis time and enantiomeric resolution was carried out. In pCEC mode, the highest chromatography performance was obtained applying +2.5kV voltage and inlet pressure 10bar. Under these conditions, the analysis times were shorter than 20min, and chromatographic efficiencies were in the range 33,000–49,000 plates/m (first eluted peak).The solvent versatility of packed i- ADMPC capillary column was also investigated. In nano-LC, the CSP was stressed under the use of strong organic solvents such as ethyl acetate, acetone and methyl t-butyl ether (MTBE). After at least 40 working hours and over 50 sample injections, the CSP resulted to be very stable allowing to achieve good repeatability employing again the mobile phase containing polar organic solvent. Enantioresolutions and chromatographic efficiencies decreased by 1.60 and 10%, respectively as the result of using above mentioned strong solvents.

Publication date: 20 October 2017
Source:Journal of Chromatography A, Volume 1520

Author(s): Giovanni D’Orazio, Chiara Fanali, Marina Karchkhadze, Bezhan Chankvetadze, Salvatore Fanali

A new experimental chiral stationary phase containing amylose 3,5-dimethylphenylcarbamate immobilized onto silica gel (i-ADMPC) was packed in 100μm I.D. fused silica capillary and used for the chiral separation of eight selected flavanone derivatives in polar organic mobile phase by using different miniaturized techniques, such as nano-liquid chromatography (nano-LC), capillary electrochromatography (CEC) and pressure-assisted CEC (pCEC). A comparative study of different elution modes in terms of chromatographic efficiency, analysis time and enantiomeric resolution was carried out. In pCEC mode, the highest chromatography performance was obtained applying +2.5kV voltage and inlet pressure 10bar. Under these conditions, the analysis times were shorter than 20min, and chromatographic efficiencies were in the range 33,000–49,000 plates/m (first eluted peak). The solvent versatility of packed i- ADMPC capillary column was also investigated. In nano-LC, the CSP was stressed under the use of strong organic solvents such as ethyl acetate, acetone and methyl t-butyl ether (MTBE). After at least 40 working hours and over 50 sample injections, the CSP resulted to be very stable allowing to achieve good repeatability employing again the mobile phase containing polar organic solvent. Enantioresolutions and chromatographic efficiencies decreased by 1.60 and 10%, respectively as the result of using above mentioned strong solvents.





A useful strategy based on chromatographic data combined with quality-by-design approach for food analysis applications. The case study of furanic derivatives in sugarcane honey

Publication date: 20 October 2017
Source:Journal of Chromatography A, Volume 1520
Author(s): Pedro Silva, Catarina L. Silva, Rosa Perestrelo, Fernando M. Nunes, José S. Câmara
Sugarcane honey (SCH) is one of the Madeira Island products par excellence and it is now popular worldwide. Its sui generis and peculiar sensory properties, explained by a variety of volatile compounds including furanic derivatives (FDs), arise mainly from manufacturing and storage conditions. A simple high-throughput approach based on semi-automatic microextraction by packed sorbent (MEPS) combined with ultra-high performance liquid chromatography (UHPLC) was developed and validated for identification and quantification of target FDs in sugarcane honey. A Quality-by-Design (QbD) approach was used as a powerful strategy to optimize analytical conditions for high throughput analysis of FDs in complex sugar-rich food matrices. The optimum point into MEPS-Method Operable Design: Region (MODR) was obtained with R-CX sorbent, acetonitrile (ACN) as elution solvent, three loading cycles and 500μL of sample volume. The optimum point into UHPLC-MODR was obtained with a CORTECS column operating at a temperature of 50°C, ACN as eluent and a flow rate of 125μLmin−1. The robustness was demonstrated by Monte Carlo simulation and capability analysis for estimation of residual errors. The concentration-response relationship for all FDs were described by polynomial function models, being confirmed by Fisher variance (F-test). The% recoveries were in a range of 91.9-112.1%. Good method precision was observed, yielding relative standard deviations (RSDs) less than 4.9% for repeatability and 8.8% for intermediate precision. The limits of quantitation for the analytes ranged from 30.6 to 737.7μgkg−1. The MEPSR-CX/UHPLCCORTECS-PDA method revealed an effective and potential analytical tool for SCH authenticity control based on target analysis of FDs allowing a strict control and differentiation from other similar or adulterated products.

Publication date: 20 October 2017
Source:Journal of Chromatography A, Volume 1520

Author(s): Pedro Silva, Catarina L. Silva, Rosa Perestrelo, Fernando M. Nunes, José S. Câmara

Sugarcane honey (SCH) is one of the Madeira Island products par excellence and it is now popular worldwide. Its sui generis and peculiar sensory properties, explained by a variety of volatile compounds including furanic derivatives (FDs), arise mainly from manufacturing and storage conditions. A simple high-throughput approach based on semi-automatic microextraction by packed sorbent (MEPS) combined with ultra-high performance liquid chromatography (UHPLC) was developed and validated for identification and quantification of target FDs in sugarcane honey. A Quality-by-Design (QbD) approach was used as a powerful strategy to optimize analytical conditions for high throughput analysis of FDs in complex sugar-rich food matrices. The optimum point into MEPS-Method Operable Design: Region (MODR) was obtained with R-CX sorbent, acetonitrile (ACN) as elution solvent, three loading cycles and 500μL of sample volume. The optimum point into UHPLC-MODR was obtained with a CORTECS column operating at a temperature of 50°C, ACN as eluent and a flow rate of 125μLmin−1. The robustness was demonstrated by Monte Carlo simulation and capability analysis for estimation of residual errors. The concentration-response relationship for all FDs were described by polynomial function models, being confirmed by Fisher variance (F-test). The% recoveries were in a range of 91.9-112.1%. Good method precision was observed, yielding relative standard deviations (RSDs) less than 4.9% for repeatability and 8.8% for intermediate precision. The limits of quantitation for the analytes ranged from 30.6 to 737.7μgkg−1. The MEPSR-CX/UHPLCCORTECS-PDA method revealed an effective and potential analytical tool for SCH authenticity control based on target analysis of FDs allowing a strict control and differentiation from other similar or adulterated products.





Towards a chromatographic similarity index to establish localised Quantitative Structure-Retention Relationships for retention prediction. III Combination of Tanimoto similarity index, logP, and retention factor ratio to identify optimal analyte training sets for ion chromatography

Publication date: 20 October 2017
Source:Journal of Chromatography A, Volume 1520
Author(s): Soo Hyun Park, Paul R. Haddad, Ruth I.J. Amos, Mohammad Talebi, Roman Szucs, Christopher A. Pohl, John W. Dolan
Retention prediction for unknown compounds based on Quantitative Structure-Retention Relationships (QSRR) can lead to rapid “scoping” method development in chromatography by simplifying the selection of chromatographic parameters. The use of retention factor ratio (or k-ratio) as a chromatographic similarity index can be a potent method to cluster similar compounds into a training set to generate an accurate predictive QSRR model provided that its limitation – that the method is impractical for retention prediction for unknown compounds – is successfully addressed. In this work, we propose a localised QSRR modelling approach with the aim of compensating the critical limitation in the otherwise successful k-ratio filter-based QSRR modelling. The approach is to combine a k-ratio filter with both Tanimoto similarity (TS) and a ΔlogP index (i.e., logP-Dual filter). QSRR models for two retention parameters (a and b) in the linear solvent strength (LSS) model in ion chromatography (IC), logk=a − blog[eluent], were generated for larger organic cations (molecular mass up to 506) on a Thermo Fisher Scientific CS17 column. The application of the developed logP-Dual filter resulted in the production of successful QSRR models for 50 organic cations out of 87 in the dataset. The predicted a- and b-values of the models were then applied to the LSS model to predict the corresponding retention times. External validation showed that QSRR models for a-, b- and tR- values with excellent accuracy and predictability (Qext(F2)2 of 0.96, 0.95, and 0.96, RMSEP of 0.06, 0.02, and 0.38min) were created successfully, and these models can be employed to speed up the “scoping” phase of method development in IC.

Publication date: 20 October 2017
Source:Journal of Chromatography A, Volume 1520

Author(s): Soo Hyun Park, Paul R. Haddad, Ruth I.J. Amos, Mohammad Talebi, Roman Szucs, Christopher A. Pohl, John W. Dolan

Retention prediction for unknown compounds based on Quantitative Structure-Retention Relationships (QSRR) can lead to rapid “scoping” method development in chromatography by simplifying the selection of chromatographic parameters. The use of retention factor ratio (or k-ratio) as a chromatographic similarity index can be a potent method to cluster similar compounds into a training set to generate an accurate predictive QSRR model provided that its limitation – that the method is impractical for retention prediction for unknown compounds – is successfully addressed. In this work, we propose a localised QSRR modelling approach with the aim of compensating the critical limitation in the otherwise successful k-ratio filter-based QSRR modelling. The approach is to combine a k-ratio filter with both Tanimoto similarity (TS) and a ΔlogP index (i.e., logP-Dual filter). QSRR models for two retention parameters (a and b) in the linear solvent strength (LSS) model in ion chromatography (IC), logk = ablog[eluent], were generated for larger organic cations (molecular mass up to 506) on a Thermo Fisher Scientific CS17 column. The application of the developed logP-Dual filter resulted in the production of successful QSRR models for 50 organic cations out of 87 in the dataset. The predicted a- and b-values of the models were then applied to the LSS model to predict the corresponding retention times. External validation showed that QSRR models for a-, b- and tR - values with excellent accuracy and predictability (Qext(F2) 2 of 0.96, 0.95, and 0.96, RMSEP of 0.06, 0.02, and 0.38min) were created successfully, and these models can be employed to speed up the “scoping” phase of method development in IC.





Determination of molar masses of macromolecules by size exclusion chromatography-light scattering not requiring knowledge of refractive index increments

Publication date: 20 October 2017 Source:Journal of Chromatography A, Volume 1520 Author(s): Simona Lavric, Jasmin Preis, Christine Rosenauer, Wolfgang Radke A new approach for the calibration of SEC-light scattering (SEC-LS) s…

Publication date: 20 October 2017
Source:Journal of Chromatography A, Volume 1520

Author(s): Simona Lavric, Jasmin Preis, Christine Rosenauer, Wolfgang Radke

A new approach for the calibration of SEC-light scattering (SEC-LS) setups is proposed, which requires solely the molar mass of a reference polymer. Neither the specific refractive index increment of the calibrant nor of the analyte is required. Comparison of the molar masses derived in different solvents for a large number of chemically different polymers shows that the new approach yields the same molar masses as if molar masses were derived using dn/dc to calibrate the light scattering setup. The approach therefore allows easier determination of molar masses by SEC-LS.





Future perspectives in high efficient and ultrafast chiral liquid chromatography through zwitterionic teicoplanin-based 2-μm superficially porous particles

Publication date: 20 October 2017
Source:Journal of Chromatography A, Volume 1520
Author(s): Omar H. Ismail, Michela Antonelli, Alessia Ciogli, Claudio Villani, Alberto Cavazzini, Martina Catani, Simona Felletti, David S. Bell, Francesco Gasparrini
With the aim of pushing forward the limits of high efficient and ultrafast chiral liquid chromatography, a new Chiral Stationary Phase (CSP) has been prepared by covalently bonding the teicoplanin selector on 2.0μm Superficially Porous Particles (SPPs). An already validated bonding protocol, which permits to achieve teicoplanin-based CSPs exhibiting zwitterionic behaviour, has been employed to prepare not only the 2.0μm version of the CSP but also two other analogous CSPs based, respectively, on 2.7μm SPPs and 1.9μm Fully Porous Particles (FPPs). The kinetic performance of these CSPs has been compared through the analysis of both van Deemter curves and kinetic plots by employing in-house packed columns of 4.6mm internal diameter and different lengths (20, 50 and 100mm). In particular on the columns packed with 2.0μm SPPs, extremely large efficiencies were observed for both achiral (>310,000 theoretical plates/meter, N/m; hr: 1.61) and chiral compounds (>290,000 N/m; hr: 1.72) in HILIC conditions. Thanks to their efficiency and enantioselectivity, these CSPs were successfully employed in ultrafast chiral separations. As an example, the enantiomers of haloxyfop were baseline resolved in about 3s, with a resolution higher than 2.0, (flow rate: 8mL/min) on a 2cm long column packed with the 2.0μm chiral SPPs.

Publication date: 20 October 2017
Source:Journal of Chromatography A, Volume 1520

Author(s): Omar H. Ismail, Michela Antonelli, Alessia Ciogli, Claudio Villani, Alberto Cavazzini, Martina Catani, Simona Felletti, David S. Bell, Francesco Gasparrini

With the aim of pushing forward the limits of high efficient and ultrafast chiral liquid chromatography, a new Chiral Stationary Phase (CSP) has been prepared by covalently bonding the teicoplanin selector on 2.0μm Superficially Porous Particles (SPPs). An already validated bonding protocol, which permits to achieve teicoplanin-based CSPs exhibiting zwitterionic behaviour, has been employed to prepare not only the 2.0μm version of the CSP but also two other analogous CSPs based, respectively, on 2.7μm SPPs and 1.9μm Fully Porous Particles (FPPs). The kinetic performance of these CSPs has been compared through the analysis of both van Deemter curves and kinetic plots by employing in-house packed columns of 4.6mm internal diameter and different lengths (20, 50 and 100mm). In particular on the columns packed with 2.0μm SPPs, extremely large efficiencies were observed for both achiral (>310,000 theoretical plates/meter, N/m; hr: 1.61) and chiral compounds (>290,000 N/m; hr: 1.72) in HILIC conditions. Thanks to their efficiency and enantioselectivity, these CSPs were successfully employed in ultrafast chiral separations. As an example, the enantiomers of haloxyfop were baseline resolved in about 3s, with a resolution higher than 2.0, (flow rate: 8mL/min) on a 2cm long column packed with the 2.0μm chiral SPPs.