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Christopher A. Pohl - One of the best experts on this subject based on the ideXlab platform.
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Dual Electrolytic Eluent Generation for Oligosaccharides Analysis Using High-Performance Anion-Exchange Chromatography.
Analytical chemistry, 2018Co-Authors: Yongjing Chen, Yan Liu, Victor Barreto, Andy Woodruff, Christopher A. PohlAbstract:The research on oligosaccharides is growing and gaining in importance at a rapid pace. The efforts to understand their bioactivity and to develop new products based on oligosaccharides in biotherapeutics and food industry require effective and reliable tools for analysis of oligosaccharides. Here we present a dual electrolytic Eluent generation platform for the analysis of oligosaccharides by high-performance anion-exchange liquid chromatography (HPAE) in both analytical and capillary column formats. The system consists of one Eluent generator producing methanesulfonic acid (MSA) connected in series with a second Eluent generator producing potassium hydroxide (KOH). Through manipulating the concentration output of both Eluent generators, chromatographic performance comparable to that obtained using the conventional sodium acetate/sodium hydroxide (NaOAc/NaOH) Eluents is achieved using the electrolytically generated potassium methanesulfonate/potassium hydroxide (KMSA/KOH) Eluent. This platform utilizes de...
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A new suppressor design for low noise performance with carbonate Eluents for Ion Chromatography.
Talanta, 2018Co-Authors: Kannan Srinivasan, Brittany K. Omphroy, Rong Lin, Christopher A. PohlAbstract:Carbonate and bicarbonate based Eluents have been applied for ion analysis from the inception of ion chromatography. The product of suppression with carbonate and/or bicarbonate Eluent is carbonic acid which is weakly dissociated and tends to outgas. While the act of suppression enhanced the signal for fully dissociated ions and lowered the background to a weakly dissociated level, the overall noise performance, however, varied depending on the suppression mechanism. Chemical suppression with a membrane suppressor yielded low noise performance with carbonate and/or bicarbonate Eluents. Electrolytic suppression, on the other hand, resulted in a relatively higher noise with carbonate based Eluents when compared to chemical suppression. In this work, we investigated the root cause of noise with electrolytic suppressors and carbonate based Eluents. Further, a new electrolytic suppressor design based on a three-electrode design is discussed in this paper and provided low noise performance with carbonate and/or bicarbonate Eluents.
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Gradient elution in ion chromatography
Journal of Chromatography A, 2002Co-Authors: Roy D. Rocklin, Christopher A. Pohl, James Andrew SchiblerAbstract:Abstract Both theoretical and practical considerations for the use of gradient elution in ion chromatography are discussed. The theory for the dependence of an analyte's retention on Eluent concentration for both isocratic and gradient elution is presented and shown to agree with experimental results. Practical solutions to problems not encountered in isocratic ion chromatography are presented. Background conductivity changes caused by increasing Eluent concentration are greatly minimized by the use of Eluents containing salts of weak acids with p K a values greater than 7, which are converted to low-conductivity free acids in the suppressor. Sodium hydroxide based Eluents produce a minimal baseline shift. Small baseline shifts produced by other Eluents can be compensated by chemical means. Using a gradient, as many as 36 ions can be separated and eluted in one run.
Purnendu K. Dasgupta - One of the best experts on this subject based on the ideXlab platform.
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Automated Programmable Preparation of Carbonate-Bicarbonate Eluents for Ion Chromatography with Pressurized Carbon Dioxide
Analytical chemistry, 2017Co-Authors: C. Phillip Shelor, Kenji Yoshikawa, Purnendu K. DasguptaAbstract:We introduce a novel carbonate–bicarbonate Eluent generation system in which CO2 is introduced using programmable CO2 pressures across a membrane into a flowing solution of electrodialytically generated high purity KOH. Many different gradient types are possible, including situations where gradients are run both on the [KOH] and the CO2 pressure. The system is more versatile than current electrodialytic carbonate Eluent generators and can easily generate significantly higher Eluent concentrations (at least to 40 mM carbonate), paving the way for future higher capacity columns. Demonstrably purer carbonate–bicarbonate Eluent systems are possible compared to manually prepared carbonate–bicarbonate Eluents and with considerable savings in time. Performance in different modes is examined. The dissolved CO2 is removed by a carbon dioxide removal device prior to detection. Best case noise levels are within a factor of 2–3 of best case suppressed hydroxide Eluent operation. The Eluent system allows particular la...
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Automated programmable pressurized carbonic acid Eluent ion exclusion chromatography of organic acids.
Journal of chromatography. A, 2017Co-Authors: C. Phillip Shelor, Purnendu K. DasguptaAbstract:Abstract Conductometric ion exclusion chromatography of weak acids does not enjoy the same degree of success as its counterpart in suppressed conductometric anion exchange chromatography. Compared to the latter, Eluent preparation is not automated. Commonly, a strong acid is used as the Eluent leading to a relatively high-detector background and poorer limits of detection. In addition, generally applicable gradient elution has not been possible. We introduce the automated preparation of carbonic acid Eluents at concentrations exceeding 0.15 M by introducing CO 2 into a flowing water stream through the walls of a Teflon AF ® capillary tube under pressure; the resulting Eluent concentration is controlled by varying the CO 2 pressure in a programmed manner. The acidic carbonic acid solution functions as the Eluent and can be almost completely removed (detector background 1.2–1.6 μS/cm) by an improved carbon dioxide removal device before detection. Theoretical and practical considerations are discussed and illustrative isocratic and gradient ion exclusion chromatography is demonstrated.
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A multifunctional dual membrane electrodialytic Eluent generator for capillary ion chromatography.
Journal of chromatography. A, 2009Co-Authors: Bingcheng Yang, Feifang Zhang, Xinmiao Liang, Purnendu K. DasguptaAbstract:A multifunctional electrodialytic generator (EDG) for capillary ion chromatography (CIC) is described. The same device can generate acidic, basic or saline Eluents. Two oppositely charged ion exchange beads are used to fabricate the EDG; the dual ion exchanger configuration ensures the production of gas-free Eluent, obviating the need of a gas removal device used with single ion exchanger EDG's. The ability of the same EDG to produce different Eluents is governed solely by the choice of the respective feed solutions; this is presently demonstrated by generation of diverse Eluents such as Na(2)CO(3)/NaHCO(3). CH(3)SO(3)H, and KNO(3). The EDG is implemented simply in a commercial cross fitting and has been tested up pressures to 2000 psi. Under typical operating conditions, the zero current concentration (open circuit penetration, OCP) is negligible. The generated Eluent concentration linearly increases with applied current with a slope that is essentially Faradaic. The device permits both isocratic and gradient operation with good reproducibility, as demonstrated by the analysis of anions using HCO(3)-/CO(3)(2-) EDG. (c) 2009 Elsevier B.V. All rights reserved.
Jon F. Parcher - One of the best experts on this subject based on the ideXlab platform.
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comparison of concentration pulse and tracer pulse chromatography experimental determination of Eluent uptake by bridged ethylene hybrid ultra high performance liquid chromatography packings
Journal of Chromatography A, 2012Co-Authors: Mei Wang, Jon F. Parcher, Bharathi Avula, Yanhong Wang, Ikhlas A KhanAbstract:Abstract Excess volume isotherms of acetonitrile and methanol sorbed on a C 18 BEH UHPLC packing were determined over a range of pressure, temperature, flow rate and Eluent composition. The isotherm measurements were carried out by two independent experimental methods, viz. , concentration pulse and tracer pulse chromatographies. Isotherms were measured with both experimental techniques at 30, 45 and 60 °C. The excess isotherms increased with decreasing temperature although the variations were relatively small. Direct comparison of the two experimental techniques showed that the measured void volumes were identical within experimental error. The measured excess volumes by both techniques were comparable with the concentration pulse experiments producing slightly higher excess volume data with highly aqueous Eluents. Both experimental techniques show some variations of the retention volumes with sample volume, sample composition, flow rate and column inlet pressure. The results confirmed the validity of both concentration and tracer pulse chromatographies for the determination of column void volumes and the excess volume of Eluent taken up by UHPLC packings.
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Sorption isotherms of ternary Eluents in reversed-phase liquid chromatography.
Analytical chemistry, 2009Co-Authors: Mei Wang, Jennifer Mallette, Jon F. ParcherAbstract:The experimental technique of mass spectrometric tracer pulse chromatography was used to measure the excess volume of each Eluent component for binary and ternary mixtures of water, acetonitrile, and methanol on a C18-bonded silica RPLC packing over the full composition range. The tracer pulse method allowed the direct measurement of excess volumes of each Eluent component without numerical integration, assumed isotherm equation, detector calibration, or off-line analysis of the Eluent composition. Absolute isotherms were estimated from the experimental data for excess volumes by use of various strategies for the estimation of the volumes of the stationary and mobile phases in dynamic equilibrium with Eluents of varying composition. The results indicate that all three Eluent components interacted with the alkane bonded phase. Some components were selectively taken up as part of the stationary phase while other components were selectively excluded so the composition of Eluent in or on the stationary phase ...
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Mass spectrometric tracer pulse chromatographic investigations of Eluent sorption with bonded RPLC packings.
Analytical chemistry, 2008Co-Authors: Mei Wang, Jennifer Mallette, Jon F. ParcherAbstract:The experimental technique of mass spectrometric tracer pulse chromatography was used to investigate the uptake of RPLC Eluents by a C18-bonded packing. The experiments were carried out with Eluents consisting of binary aqueous mixtures with acetonitrile, methanol, and tetrahydrofuran over the full range of Eluent composition at 25 °C. The primary experimental data obtained were excess volumes of sorption for the Eluent components. The excess volume data were then used to determine the absolute volume of each Eluent component in the stationary phase as a function of composition. The absolute volumes were calculated by utilizing a series of strategies specific to limited Eluent composition range. The linear inflection region of the excess volume isotherms was used to calculate the volume and composition of the Eluent in the stationary phase for organic-rich Eluents. Three different assumptions were used and evaluated for the water-rich Eluent compositions. The assumptions were (i) constant volume of the so...
Mei Wang - One of the best experts on this subject based on the ideXlab platform.
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comparison of concentration pulse and tracer pulse chromatography experimental determination of Eluent uptake by bridged ethylene hybrid ultra high performance liquid chromatography packings
Journal of Chromatography A, 2012Co-Authors: Mei Wang, Jon F. Parcher, Bharathi Avula, Yanhong Wang, Ikhlas A KhanAbstract:Abstract Excess volume isotherms of acetonitrile and methanol sorbed on a C 18 BEH UHPLC packing were determined over a range of pressure, temperature, flow rate and Eluent composition. The isotherm measurements were carried out by two independent experimental methods, viz. , concentration pulse and tracer pulse chromatographies. Isotherms were measured with both experimental techniques at 30, 45 and 60 °C. The excess isotherms increased with decreasing temperature although the variations were relatively small. Direct comparison of the two experimental techniques showed that the measured void volumes were identical within experimental error. The measured excess volumes by both techniques were comparable with the concentration pulse experiments producing slightly higher excess volume data with highly aqueous Eluents. Both experimental techniques show some variations of the retention volumes with sample volume, sample composition, flow rate and column inlet pressure. The results confirmed the validity of both concentration and tracer pulse chromatographies for the determination of column void volumes and the excess volume of Eluent taken up by UHPLC packings.
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Sorption isotherms of ternary Eluents in reversed-phase liquid chromatography.
Analytical chemistry, 2009Co-Authors: Mei Wang, Jennifer Mallette, Jon F. ParcherAbstract:The experimental technique of mass spectrometric tracer pulse chromatography was used to measure the excess volume of each Eluent component for binary and ternary mixtures of water, acetonitrile, and methanol on a C18-bonded silica RPLC packing over the full composition range. The tracer pulse method allowed the direct measurement of excess volumes of each Eluent component without numerical integration, assumed isotherm equation, detector calibration, or off-line analysis of the Eluent composition. Absolute isotherms were estimated from the experimental data for excess volumes by use of various strategies for the estimation of the volumes of the stationary and mobile phases in dynamic equilibrium with Eluents of varying composition. The results indicate that all three Eluent components interacted with the alkane bonded phase. Some components were selectively taken up as part of the stationary phase while other components were selectively excluded so the composition of Eluent in or on the stationary phase ...
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Mass spectrometric tracer pulse chromatographic investigations of Eluent sorption with bonded RPLC packings.
Analytical chemistry, 2008Co-Authors: Mei Wang, Jennifer Mallette, Jon F. ParcherAbstract:The experimental technique of mass spectrometric tracer pulse chromatography was used to investigate the uptake of RPLC Eluents by a C18-bonded packing. The experiments were carried out with Eluents consisting of binary aqueous mixtures with acetonitrile, methanol, and tetrahydrofuran over the full range of Eluent composition at 25 °C. The primary experimental data obtained were excess volumes of sorption for the Eluent components. The excess volume data were then used to determine the absolute volume of each Eluent component in the stationary phase as a function of composition. The absolute volumes were calculated by utilizing a series of strategies specific to limited Eluent composition range. The linear inflection region of the excess volume isotherms was used to calculate the volume and composition of the Eluent in the stationary phase for organic-rich Eluents. Three different assumptions were used and evaluated for the water-rich Eluent compositions. The assumptions were (i) constant volume of the so...
Yoshio Okamoto - One of the best experts on this subject based on the ideXlab platform.
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synthesis and application of immobilized polysaccharide based chiral stationary phases for enantioseparation by high performance liquid chromatography
Journal of Chromatography A, 2014Co-Authors: Jun Shen, Tomoyuki Ikai, Yoshio OkamotoAbstract:Polysaccharide-based chiral stationary phases (CSPs) or chiral packing materials (CPMs) have been frequently employed for analyzing and separating various enantiomers by high-performance liquid chromatography (HPLC). The polysaccharide derivatives dissolved in a solvent are usually coated on silica gel to be used as CSPs. This means that some solvents, which can swell or dissolve the derivatives, cannot be used as the Eluents in HPLC. In this review, various immobilization methods of the polysaccharide derivatives are described. The immobilization often reduces the chiral recognition ability compared to that of the corresponding coated-type CSPs. This problem can be overcome by the versatility of Eluent selection for the immobilized CSPs. Enantioseparations of various racemates on the immobilized commercial columns using the non-standard Eluents are briefly summarized.