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Schurig V. Elaborate treatment of retention in chemoselective chromatography--the retention increment approach and non-linear effects. J Chromatogr A 2008; 1216:1723-36. [PMID: 19070865 DOI: 10.1016/j.chroma.2008.11.016] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2008] [Revised: 11/07/2008] [Accepted: 11/10/2008] [Indexed: 11/27/2022]
Abstract
The retention increment approach is described which quantifies the association equilibria of a selectand and a selector in complexation and inclusion chromatography. A thermodynamic treatment of enantioselectivity based on retention phenomena in chromatography including entropy/enthalpy compensation and the isoenantioselective temperature is advanced. Kinetic parameters of enantiomerization are discussed. Non-linear effects, both existent and elusive, are described and proposed, respectively. The enantioselectivity pertaining to catalysis vs. chromatography is compared and a unified nomenclature is proposed. Through an educational effort, this account is aimed at providing a deeper insight into chemoselective aspects of chromatography thereby stimulating further research of both established and speculative phenomena of the most intriguing manifestation of chemoselectivity, that is, of enantioselectivity.
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Affiliation(s)
- Volker Schurig
- Institute of Organic Chemistry, University of Tübingen, 72076 Tübingen, Germany.
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2
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Gas chromatographic high-throughput screening techniques in catalysis. J Chromatogr A 2007; 1184:160-90. [PMID: 18035362 DOI: 10.1016/j.chroma.2007.10.086] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2007] [Revised: 10/09/2007] [Accepted: 10/29/2007] [Indexed: 11/23/2022]
Abstract
Discovering highly efficient catalysts is of great scientific and economical interest. Advances in high-throughput assays in combination with sophisticated analytical techniques have increased the rapidity with which catalysts can be identified and optimized. Understanding how kinetics in the mechanism of catalysis is controlled by structural parameters is essential for a directed design of catalysts. To identify such rate-controlling elementary steps and to develop and refine models, comprehensive experimental kinetic data of a broad variety of substrates are necessary. In the present article concepts of high-throughput screening techniques in catalysis using gas chromatography are reviewed in a survey covering the period from 1998 to 2007. To cover also the origins of concepts and groundbreaking experiments in this research area milestones going back to 1950 are also reviewed. The first part of the review will focus on off-line gas chromatographic analysis, the second part on on-line gas chromatographic analysis covering sequential, parallelized and high-throughput multiplexing gas chromatography. The third part presents recent advances in the integration of chemical transformation and analysis in gas chromatography. The present review article describes the state-of-the-art, scope and limitations, and applications of these different high-throughput screening approaches.
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MENSAH PAUL, CARTA GIORGIO. DYNAMICS OF ADSORPTIVE REACTOR WITH A BIMOLECULAR REACTION. CHEM ENG COMMUN 2007. [DOI: 10.1080/00986449908912146] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- PAUL MENSAH
- a Department of Chemical Engineering , University of Virginia , Charlottesville, VA, 22903-2442
| | - GIORGIO CARTA
- a Department of Chemical Engineering , University of Virginia , Charlottesville, VA, 22903-2442
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Trapp O. Unified Equation for Access to Rate Constants of First-Order Reactions in Dynamic and On-Column Reaction Chromatography. Anal Chem 2006; 78:189-98. [PMID: 16383327 DOI: 10.1021/ac051655r] [Citation(s) in RCA: 140] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A unified equation to evaluate elution profiles of reversible as well as irreversible (pseudo-) first-order reactions in dynamic chromatography and on-column reaction chromatography has been derived. Rate constants k1 and k(-1) and Gibbs activation energies are directly obtained from the chromatographic parameters (retention times tR(A) and tR(B) of the interconverting or reacting species A and B, the peak widths at half-height wA and wB, and the relative plateau height h(p)), the initial amounts A0 and B0 of the reacting species, and the equilibrium constant K(A/B). The calculation of rate constants requires only a few iterative steps without the need of performing a computationally extensive simulation of elution profiles. The unified equation was validated by comparison with a data set of 125,000 simulated elution profiles to confirm the quality of this equation by statistical means and to predict the minimal experimental requirements. Surprisingly, the recovery rate from a defined data set is on average 35% higher using the unified equation compared to the evaluation by iterative computer simulation.
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Affiliation(s)
- O Trapp
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany.
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Polyakova IV, Pisarev OA. Influence of polyfunctional interactions between organic zwitter-ion eremomycin and carboxylic cation exchangers on forming concentration front. J Chromatogr A 2005; 1092:135-41. [PMID: 16188568 DOI: 10.1016/j.chroma.2005.07.017] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2004] [Revised: 06/22/2005] [Accepted: 07/07/2005] [Indexed: 10/25/2022]
Abstract
The nature of the polyfunctional interactions between the organic zwitter-ions of eremomycin and the carboxylic sorbents was studied. A cation exchange and hydrophobic mechanisms of interactions in the studied sorption system were determined as preponderant over other ones. The typical features of the eremomycin diffusion into the pores of the structurally segregated carboxylic sorbents were studied. The physical-chemical properties of the sorption system which influence the formation of the target product concentration zone with sharp boundary were investigated. The effect of column sizes on the eremomycin unified elution peak formation was shown. The height to diameter ratio leading to the eremomycin concentration front division into two zones was determined.
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Affiliation(s)
- Irina V Polyakova
- Department of Biopolymers, Institute of Macromolecular Compounds, Russian Academy of Sciences, Bolshoi Pr. 31, 199004, St. Petersburg, Russia.
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Zhang WN, Hu ZX, Feng YQ, Da Shi-Lu. Optimization of parameters of high-performance displacement chromatography for separation of soybean phosphatidylcholine and phosphatidylethanolamine. J Chromatogr A 2005; 1068:269-78. [PMID: 15830933 DOI: 10.1016/j.chroma.2005.01.084] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Hundred milligrams of soybean phospholipids were successfully separated by using high-performance displacement chromatography (HPDC) on a 150mm x 4.6mm analytical silica column (3-5 microm packings) with dichloromethane-methanol (9:1, v/v) as carrier and ethanolamine as displacer. From the viewpoint of preparative separation, the effects of loading amount, concentration and flow-rate of displacer on separation efficiency were investigated using throughput and recovery as indices. The parameters were optimized by orthogonal test design and statistical analysis method. Under the optimum conditions, namely displacer concentration being 167 mM, the flow-rate of displacer at 0.2 ml/min and concentration of sample being 211 mg/ml (factual loading amount 211 mg/ml x 0.7 ml = 148 mg), the purity, throughput and recovery of obtained soybean phosphatidylethanolamine (PE) and phosphatidylcholine (PC) were 80.2%, 65.7 mg/h, 70.9% and 90.5%, 272.6 mg/h, 88.3%, respectively. In addition, selections of regenerant and appropriate regeneration condition were also studied.
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Affiliation(s)
- Wei-Nong Zhang
- Department of Chemistry, Wuhan University, 430072, China
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Zhang WN, He HB, Feng YQ, Da SL. Separation of phosphatidylcholine and phosphatidylethanolamine by using high-performance displacement chromatography. J Chromatogr A 2004; 1036:145-54. [PMID: 15146915 DOI: 10.1016/j.chroma.2004.02.079] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
A binary mixture of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) was successfully separated by high-performance displacement chromatography (HPDC) on an 150 mm x 4.6 mm analytical silica column (3-5 microm packing), using dichloromethane-methanol (9:1, v/v) as carrier and ethanolamine as displacer. The effects of displacer concentration, flow-rate, loading amount and the composition of the sample on separation efficiency were studied. Eighty-four milligrams sample (PE:PC 1:1.16) was separated perfectly by using 83 mM ethanolamine (in carrier) as displacer at the flow-rate of 0.1 ml/min. The yields of the pure PE and PC (100% purity) were 94.8% and 87.9%, respectively and the cycle time for a single separation was about 195 min. It was valuable that the optimum loading amount (the allowed maximum of sample loading) was investigated only by using the sample to be simulated the composition of the separated actual one, because the separation efficiency was significantly affected by the composition of the sample. For the same loading amount of 175 mg, the yields of the pure PE and PC were improved greatly from 31.4 and 16.9 to 56.0 and 77.6%, respectively, when the proportion of PE to PC was adjusted from 1:1.16 to 1:4. Furthermore, the separation of PE and PC in an actual sample (soybean phospholipids) was achieved using the proposed HPDC method.
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Affiliation(s)
- Wei-Nong Zhang
- Department of Chemistry, Wuhan University, Wuhan 430072, China
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Abstract
Displacement chromatography was successfully used to separate a binary isomer mixture, epirubicin and doxorubicin, on Kromasil KR100-10 C18 250x4.6 mm I.D. (10 microm) column. Displacement parameters such as the types and the concentrations of displacer, the composition and the flow rate of the mobile phase were critically examined in this study. The displacer employed was 30 mg/ml benzethonium chloride. Loading of feed at lower initial organic level of mobile phase coupled with displacement at higher organic level was found to give efficient separation. A 30-mg amount of binary isomer mixture was separated on an analytical column. The purification of epirubicin from the closely related impurities present in raw product solution by displacement chromatography was also investigated. The purity of epirubicin required was greater than 99% with a recovery of 60%. The results have indicated that this process made good use of the high feed load, low solvent costs, and high resolution characteristics of displacement chromatography and offered the chromatographic engineer a powerful tool for the preparative purification of therapeutic compounds.
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Affiliation(s)
- Yan Qi
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing
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Schoetz G, Trapp O, Schurig V. Determination of the cis-trans isomerization barrier of several L-peptidyl-L-proline dipeptides by dynamic capillary electrophoresis and computer simulation. Electrophoresis 2001; 22:2409-15. [PMID: 11519944 DOI: 10.1002/1522-2683(200107)22:12<2409::aid-elps2409>3.0.co;2-c] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Dynamic capillary electrophoresis (DCE) and computer simulation of the elution profiles with the theoretical plate and the stochastic model has been applied to determine the isomerization barriers of the three dipeptides L-alanyl-L-proline, L-leucyl-L-proline, and L-phenylalanyl-L-proline. The separation of the rotational cis-trans isomers has been performed in an aqueous 70 mM borate buffer at pH 9.5. Interconversion profiles featuring plateau formation and peak broadening were observed. To determine the rate constants k1 and k(-1) of the cis-trans isomerization in dynamic capillary electrophoresis, equations have been derived for the theoretical plate model and stochastic model. The electropherograms were simulated with the ChromWin software which uses the experimental data plateau height h(plateau), peak width at half height Wh, the total migration times of the cis-trans isomers tR and the electroosmotic break-through time t0 as well as the peak ratio [cis]/[trans]. From temperature-dependent measurements, the rate constants k1 and k(-1) and the kinetic activation parameters deltaG#, deltaH# and deltaS# of the cis-trans isomerization of the three dipeptides were obtained.
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Affiliation(s)
- G Schoetz
- Universität Tübingen, Institut für Organische Chemie, Germany
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Trapp O, Caccamese S, Schmidt C, Böhmer V, Schurig V. Enantiomerization of an inherently chiral resorcarene derivative: determination of the interconversion barrier by computer simulation of the dynamic HPLC experiment. ACTA ACUST UNITED AC 2001. [DOI: 10.1016/s0957-4166(01)00246-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Trapp O, Schurig V. Approximation function for the direct calculation of rate constants and Gibbs activation energies of enantiomerization of racemic mixtures from chromatographic parameters in dynamic chromatography. J Chromatogr A 2001; 911:167-75. [PMID: 11293578 DOI: 10.1016/s0021-9673(00)01259-0] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
An approximation function for enantioselective dynamic chromatography of racemic mixtures of interconverting enantiomers has been derived that allows the direct calculation of enantiomerization rate constants (k1 and k(-1)) and Gibbs activation energies of enantiomerization, deltaG++ , from chromatographic parameters, i.e., retention times of the enantiomers A and B ((t(A)R and t(B)R), peak widths at half height (WA and wB) and the relative plateau height (hplateau), without computer simulation. The reaction rate constants of enantiomerization, k(-1), obtained with this approximation function, have been validated by comparison with a simulated dataset of 15,625 chromatograms. The mean, standard deviation and confidence interval show a high correlation between the approximated and simulated rate constants. The average deviation from the Gibbs activation enthalpy of enantiomerization, deltaG++, has been estimated to be as small as about +/- 0.11 RT.
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Affiliation(s)
- O Trapp
- Institute of Organic Chemistry, University of Tübingen, Germany.
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9 Bioseparations by displacement chromatography. ACTA ACUST UNITED AC 2000. [DOI: 10.1016/s0149-6395(00)80056-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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