1
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Chiral Separation of d,l-p-Hydroxyphenylglycine by Ligand Exchange Micellar Electrokinetic Capillary Chromatography. Chromatographia 2015. [DOI: 10.1007/s10337-015-2873-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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2
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Liu R, Du Y, Chen J, Zhang Q, Du S, Feng Z. Investigation of the Enantioselectivity of Tetramethylammonium L-hydroxyproline Ionic Liquid as a Novel Chiral Ligand in Ligand-Exchange CE and Ligand-Exchange MEKC. Chirality 2014; 27:58-63. [DOI: 10.1002/chir.22388] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2014] [Revised: 08/12/2014] [Accepted: 08/13/2014] [Indexed: 11/12/2022]
Affiliation(s)
- Ruijuan Liu
- Department of Analytical Chemistry; China Pharmaceutical University; Nanjing People's Republic of China
| | - Yingxiang Du
- Department of Analytical Chemistry; China Pharmaceutical University; Nanjing People's Republic of China
- Key Laboratory of Drug Quality Control and Pharmacovigilance (Ministry of Education); China Pharmaceutical University; Nanjing People's Republic of China
- State Key Laboratory of Natural Medicines; China Pharmaceutical University; Nanjing People's Republic of China
| | - Jiaquan Chen
- Department of Analytical Chemistry; China Pharmaceutical University; Nanjing People's Republic of China
| | - Qi Zhang
- Department of Analytical Chemistry; China Pharmaceutical University; Nanjing People's Republic of China
| | - Shuaijing Du
- College of Chemistry and Molecular Engineering; Peking University; Beijing People's Republic of China
| | - Zijie Feng
- Department of Analytical Chemistry; China Pharmaceutical University; Nanjing People's Republic of China
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3
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Zhang H, Qi L, Mao L, Chen Y. Chiral separation using capillary electromigration techniques based on ligand exchange principle. J Sep Sci 2012; 35:1236-48. [PMID: 22733505 DOI: 10.1002/jssc.201200067] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Over the last couple of decades, researchers have developed diverse chiral separation methods emerged from a few chiral separation principles. This review article is primarily focused on the application of chiral ligand-exchange (CLE) principle in capillary electromigration techniques, such as capillary electrophoresis (CE) and capillary electrochromatography (CEC). First, the most commonly used CLE-CZE separation mode by using different kinds of central ions, such as Cu(II), Zn(II), borate ion, and other metal ions, has been introduced. Meanwhile, several kinds of surfactants have been applied as the micelle-forming agents in the CLE micellar electrokinetic chromatography mode. The highlight of recent research of CLE-CEC is the exploitation of novel columns for chiral separation. Then, two kinds of capillary columns, packed capillary and monolithic capillary column, have been briefly described. Finally, the effective application of these chiral separation methods has been presented, including the application in life science and food analysis area.
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Affiliation(s)
- Haizhi Zhang
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Analytical Chemistry for Living Biosystems, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China
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4
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Schmid MG. Chiral metal-ion complexes for enantioseparation by capillary electrophoresis and capillary electrochromatography: a selective review. J Chromatogr A 2012; 1267:10-6. [PMID: 22897866 DOI: 10.1016/j.chroma.2012.07.088] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2012] [Revised: 07/20/2012] [Accepted: 07/23/2012] [Indexed: 11/30/2022]
Abstract
This review gives an overview about chiral separation by capillary electrophoresis and capillary electrochromatography using different chiral metal-ion complexes. The topic enantioseparation is still of big interest for chiral drugs and natural compounds. Regarding chiral drugs it is often the case that the enantiomers differ in activity. The chiral separation principle of ligand-exchange (LE) can be enabled for liquid chromatography, capillary electrophoresis as well as for capillary electrochromatography. Ligand-exchange can be applied particularly for chiral amino acids, amino alcohols or α-hydroxy acids. Examples and applications are given along with the latest developments.
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Affiliation(s)
- M G Schmid
- Institute of Pharmaceutical Sciences, Department of Pharmaceutical Chemistry, Karl-Franzens-University, Graz, Austria.
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5
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Kartsova LA, Alekseeva AV. Ligand-exchange capillary electrophoresis. JOURNAL OF ANALYTICAL CHEMISTRY 2011. [DOI: 10.1134/s1061934811050066] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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6
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Schmid MG, Gübitz G. Enantioseparation by chromatographic and electromigration techniques using ligand-exchange as chiral separation principle. Anal Bioanal Chem 2011; 400:2305-16. [DOI: 10.1007/s00216-011-4737-5] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2010] [Revised: 12/21/2010] [Accepted: 01/27/2011] [Indexed: 11/24/2022]
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7
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Hödl H, Koidl J, Schmid MG, Gübitz G. Chiral resolution of tryptophan derivatives by CE using canine serum albumin and bovine serum albumin as chiral selectors. Electrophoresis 2006; 27:4755-62. [PMID: 17136718 DOI: 10.1002/elps.200600425] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
This work deals with the application of BSA and canine serum albumin (CSA) for enantioseparation of tryptophan derivatives with CE. The aim of this work was the investigation of the influence of different functional groups of tryptophan derivatives on enantioseparation. CSA as a chiral selector was tested to compare its selector properties with those of BSA. The enantiomers of the tryptophan derivatives were separated by adding BSA or CSA to the BGE. The influence of pH, temperature, BSA and CSA concentration and organic modifiers was investigated. It was found that the stereoselectivity for the different tryptophan derivatives is dependent on the albumin species. It turned out that the different functional groups of the derivatives showed a significant influence on stereoselectivity.
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Affiliation(s)
- Heike Hödl
- Institute of Pharmaceutical Sciences, Department of Pharmaceutical Chemistry, Karl-Franzens University, Graz, Austria
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8
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Koidl J, Hödl H, Schmid MG, Pantcheva S, Pajpanova T, Gübitz G. Chiral separation of halogenated amino acids by ligand-exchange capillary electrophoresis. Electrophoresis 2005; 26:3878-83. [PMID: 16217828 DOI: 10.1002/elps.200500130] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The chiral separation of halogenated amino acids by ligand-exchange CE is described. Halogenated amino acids attracted increasing interest in recent years because of their physiological activities. Different chiral selectors, as there are L-4-hydroxyproline, L-histidine, and N-alkyl derivatives of L-4-hydroxyproline in form of their copper(II) complexes, are compared for their chiral recognition ability for halogenated amino acids. The influence of various parameters, such as selector concentration, pH, organic modifier, and field strength, on the resolution was investigated. All halogenated amino acids investigated were baseline-separated under optimized conditions.
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Affiliation(s)
- Julia Koidl
- Department of Pharmaceutical Chemistry, Institute of Pharmaceutical Sciences, Karl-Franzens-University, Graz, Austria
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9
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Chuang SC, Chang CY, Liu CY. Polystyrene monolithic column functionalized with copper-iminodiacetate complex as a stationary phase for open tubular capillary electrochromatography. J Chromatogr A 2005; 1044:229-36. [PMID: 15354442 DOI: 10.1016/j.chroma.2004.04.070] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Polystyrene-divinylbenzene copolymer functionalized with copper-iminodiacetate complex was prepared in situ for the capillary electrochromatographic separation of amino acids and oligopeptides. The steps included silanization of the fused-silica capillary column, functionalization, polymerization, hydrolysis and complexation. For having a homogeneous polymerization system in the selected porogen, the functional monomer was obtained from the reaction of 4-vinylbenzyl chloride and diethyl iminodiacetate. Scanning electron microscopy showed that the polymeric monolith column was an open tubular column with a thickness of 0.3 microm. Various modes of hydrolysis were investigated via the electroosmatic flow measurement to find the optimization condition prior to introducing the copper ion. The influence of pH, composition and concentration of mobile phase as well as the organic modifier were investigated. Judging from our results, the recognition performance of the prepared stationary phase might be integrated from the mechanisms of ligand exchange, electrophoretic mobility, hydrophobic interaction, and hydrogen bonding.
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Affiliation(s)
- Shiu-Chun Chuang
- Department of Chemistry, National Taiwan University, Taipei 10617, Taiwan
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10
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Zheng ZX, Wei Y, Lin JM. Chiral separation based on ligand-exchange capillary electrophoresis using a copper(II)-L-ornithine ternary complex as selector. Electrophoresis 2005; 26:1007-1012. [PMID: 15714579 DOI: 10.1002/elps.200406133] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
A ligand-exchange capillary electrophoresis was explored, with L-ornithine as the ligand and copper(II) as the central ion. Its applicability was demonstrated with underivatized and dansyl amino acids, a dipeptide, and drugs with amino alcohol structure. The enantioselectivity was found to be strongly dependent on pH and copper(II)-L-Orn complex concentration. Due to the adsorption of the positively charged species onto the capillary inner walls, the chiral separation selectivity is very high while the efficiency is relatively low. Permanent 1,3-propanediamine-coated capillaries show an improved separation efficiency and theoretical plate numbers increasing from 10(4) to 10(5). Similar phenomena were observed when sodium dodecyl sulfate (SDS) micelles were added to the copper(II) complex solution. The poor separation efficiency of chiral compounds in uncoated capillaries may result from the low rate of the ligand-exchange reactions, and the high enantioselectivity may derive from the complexing process in the adsorbed phase.
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Affiliation(s)
- Zhi-Xia Zheng
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China
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11
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Wang W, Qiu B, Xu X, Zhang L, Chen G. Separation and determination of L-tryptophan and its metabolites by capillary micellar electrokinetic chromatography with amperometric detection. Electrophoresis 2005; 26:903-910. [PMID: 15714546 DOI: 10.1002/elps.200406099] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
A high-performance method of capillary micellar electrokinetic chromatography (CMEKC) with amperometric detection (AD), using a newly designed pre-aligned electrochemical cell, has been developed for the separation and determination of L-tryptophan (Trp) and its eight metabolites including 3-hydroxy-L-kynurenine (3-HK), 5-hydroxy-L-tryptophan (5-HTP), L-kynurenine (KN), 5-hydroxyindole-3-acetic acid (5-HIAA), xanthurenic acid (XA), indole-3-pyruvic acid (IPA), 5-hydroxytryptamine (5-HT), and tryptamine (Tryp). A carbon disk electrode was used as the working electrode and the optimal detection potential was 0.85 V (versus Ag/AgCl). At 24 kV of applied voltage, the nine compounds were completely separated, within 23 min, in a 10 mol/L Na(2)HPO(4)-NaOH buffer (pH 11.0) containing 40 mmol/L sodium dodecyl sulfate (SDS) and 3% methanol (v/v). A good linear relationship was obtained for all analytes in this paper and the detection limits of 3-HK, 5-HTP, KN, Trp, 5-HIAA, XA, IPA, 5-HT, and Tryp were 7.42, 5.18, 34.6, 3.99, 15.1, 12.7, 260, 6.72, and 8.01 nmol/L, respectively. This method has been applied to analyze the metabolism of Trp in rabbit urine.
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Affiliation(s)
- Wei Wang
- Department of Chemistry, Fuzhou University, Fuzhou, Fujian, China
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12
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Capillary Electrophoresis and Capillary Electrochromatography of Amino Acids as Dansyl Derivatives. ACTA ACUST UNITED AC 2005. [DOI: 10.1016/s0301-4770(05)80014-4] [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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13
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Affiliation(s)
- Zilin CHEN
- Center for Micro-fluidics and Medical Diagnostics, Department of Chemical and Biomolecular Engineering, University of Notre Dame
| | - Hsueh-Chia CHANG
- Center for Micro-fluidics and Medical Diagnostics, Department of Chemical and Biomolecular Engineering, University of Notre Dame
| | - Toshiyuki HOBO
- Department of Applied Chemistry, Graduate School of Engineering, Tokyo Metropolitan University
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14
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Nakajima H, Kawata K, Shen H, Nakagama T, Uchiyama K. Chiral Separation of NBD-Amino Acids by Ligand-Exchange Micro-Channel Electrophoresis. ANAL SCI 2005; 21:67-71. [PMID: 15675519 DOI: 10.2116/analsci.21.67] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The chiral separation of amino acid derivatives by ligand-exchange electrophoresis in a microchannel chip was performed for the first time. A Cu(II) complex with L-prolinamide was used as a chiral selector. The migration behaviors of eleven NBD-DL-amino acids were investigated by ligand-exchange capillary electrophoresis (LE-CE). The enantiomer of five NBD-amino acids (Ser, Thr, Val, Phe and His) could be separated by LE-CE using a 20 mM ammonium acetate buffer (pH 9.0) containing 10 mM copper acetate, 20 mM L-prolinamide and 1 mM SDS. NBD-His was eluted in the order D-form and L-form, while the elution order of another enantiomers was L-form and D-form. Under this condition, the enantioseparation of these five NBD-amino acids by ligand-exchange microchip electrophoresis (LE-ME) was investigated using a glass microchip. The enantioseparation of NBD-Ser, -Thr and -His could be successfully accomplished by LE-ME. LE-ME was superior to LE-CE in terms of the short migration time and a good enantiomeric separation.
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Affiliation(s)
- Hizuru Nakajima
- Department of Applied Chemistry, Graduate School of Engineering, Tokyo Metropolitan University, 1-1 Minamiohsawa, Hachioji, Tokyo 192-0397, Japan.
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15
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Chen Z, Uchiyama K, Hobo T. Chiral resolution of dansyl amino acids by ligand exchange-capillary electrophoresis using Cu(II)-l-prolinamides as chiral selector. Anal Chim Acta 2004. [DOI: 10.1016/j.aca.2004.07.024] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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16
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Electrochromatographic enantioseparation using chiral ligand exchange monolithic sol–gel column. Anal Chim Acta 2004. [DOI: 10.1016/j.aca.2003.09.012] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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17
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Zheng ZX, Lin JM, Qu F. Chiral separation of underivatized and dansyl amino acids by ligand-exchange micellar electrokinetic capillary chromatography using a copper(II)-L-valine complex as selector. J Chromatogr A 2003; 1007:189-96. [PMID: 12924564 DOI: 10.1016/s0021-9673(03)00960-9] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Ligand-exchange micellar electrokinetic capillary chromatography was used for the chiral resolution of underivatized and dansyl amino acid enantiomers simultaneously. The separation was achieved by chiral copper(II)-L-valine complexes incorporated in micelles of sodium dodecyl sulfate (SDS). The enantioresolution was strongly affected by SDS and a concentration of 20 mM SDS was shown to be necessary for the separation. Other impacting factors were investigated including pH, the molar ratio of copper(II) to L-valine and the total concentration of complex. Using the proposed method, 11 different dansyl amino acids and two underivatized amino acids were separated successfully with a running electrolyte of 20 mM NH4OAc, 4 mM CuSO4, 8 mM L-valine and 20 mM SDS at pH 9.0 in less than 25 min. Experiments were also performed with other amino acid ligands in order to vary the stability and the sterical arrangement of the copper(II) complexes and the possible chiral recognition mechanism was also discussed briefly.
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Affiliation(s)
- Zhi-Xia Zheng
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing 100085, China
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18
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Abstract
As a follow-up to a series of review articles on enantioselective ligand exchange chromatography, the present contribution critically evaluates achievements in this area of active and successful research which have been reported in the scientific since 1992. Also discussed is enantioselective ligand exchange in electromigration techniques which have developed especially fruitfully during the last decade.
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Affiliation(s)
- Vadim A Davankov
- Institute of Organo-Element Compounds, Russian Academy of Sciences, Vavilov Str. 28, Moscow 119991, Russia.
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19
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Welsch T, Michalke D. (Micellar) electrokinetic chromatography: an interesting solution for the liquid phase separation dilemma. J Chromatogr A 2003; 1000:935-51. [PMID: 12877206 DOI: 10.1016/s0021-9673(03)00503-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
High-performance liquid chromatography (HPLC) is a well-established method in modern analysis. The method is simple, very robust and is applicable to the majority of components to be analyzed in contrast to gas chromatography. Low efficiency and small peak capacity are sore points of HPLC when complex mixtures have to be separated. The reason for this dilemma is the small diffusion coefficient of the analytes in the liquid mobile phase compared to a gaseous phase. This review, complemented by exemplary calculated data and some latest results of our own research, illustrates the dilemma of liquid phase chromatography to achieve high efficiencies under reasonable conditions. It is shown that (micellar) electrokinetic chromatography, offering fast and efficient separations, is a very promising solution for this dilemma. Additional features of this method are possibilities of on-line analyte concentration, coupling to mass spectrometry and the easy change of selectivities by applying various separation additives. The pros and cons of electrokinetic chromatography are pointed out and some application examples are given.
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Affiliation(s)
- Thomas Welsch
- Department of Analytical and Environmental Chemistry, University of Ulm, Albert-Einstein-Allee 11, D-89081 Ulm, Germany.
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20
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Chen Z, Niitsuma M, Uchiyama K, Hobo T. Comparison of enantioseparations using Cu(II) complexes with L-amino acid amides as chiral selectors or chiral stationary phases by capillary electrophoresis, capillary electrochromatography and micro liquid chromatography. J Chromatogr A 2003; 990:75-82. [PMID: 12685585 DOI: 10.1016/s0021-9673(02)01970-2] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In this paper we report that Cu(II) complexes with L-amino acid amides were used as chiral selectors for enantioseparation by capillary electrophoresis, capillary electrochromatography (CEC) and micro liquid chromatography using chemically modified monolithic columns. The enantioselectivity, enantiomer migration order, and the performance have been compared when different chiral selectors were used in these modes. L-Enantiomers showed longer retention times than D-forms in both CEC and LC modes. However, it has interestingly been observed that the migration order of Dns-DL-Ser showed an exception in CEC using L-prolinamide-modified column that Dns-L-Ser was eluted as the first peak. On the basis of proposed structures of complexes in the chiral recognition, differences in migration orders and recognition mechanism were discussed.
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Affiliation(s)
- Zilin Chen
- Department of Applied Chemistry, Graduate School of Engineering, Tokyo Metropolitan University, 1-1 Minamiohsawa, Hachioji, Tokyo 192-0397, Japan.
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21
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Chen Z, Niitsuma M, Nakagama T, Uchiyama K, Hobo T. Enantioseparations of dansyl amino acids by capillary electrophoresis using Cu(II) complexes with L-amino acylamides as chiral selectors in electrolytes. J Sep Sci 2002. [DOI: 10.1002/1615-9314(20021101)25:15/17<1197::aid-jssc1197>3.0.co;2-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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22
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Lecnik O, Schmid MG, Presser A, Gübitz G. Influence of structure and chirality of the selector on the chiral recognition of amino acids using ligand-exchange capillary electrophoresis. Electrophoresis 2002; 23:3006-12. [PMID: 12207309 DOI: 10.1002/1522-2683(200209)23:17<3006::aid-elps3006>3.0.co;2-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The dependence of the chiral recognition ability and enantiomer migration order on the structure, substitution pattern and chirality of chiral selectors used in ligand-exchange capillary electrophoresis is investigated. As chiral selectors different N-alkyl derivatives of proline and hydroxyproline as their copper(II) complexes are used. The influence of the position and conformation of the hydroxy group in the hydroxyproline derivatives and of the structure and chirality of the side chain on enantioselectivity is investigated. Furthermore, the effect of surfactants such as sodium dodecyl sulfate and cetyl trimethyl ammonium bromide on resolution and enantiomer migration order is studied. The investigations were carried out with three aromatic amino acids as model compounds.
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Affiliation(s)
- Oliver Lecnik
- Institute of Pharmaceutical Chemistry and Pharmaceutical Technology, Karl-Franzens-University Graz, Graz, Austria
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23
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Lu X, Chen Y, Guo L, Yang Y. Chiral separation of underivatized amino acids by ligand-exchange capillary electrophoresis using a copper(II)-L-lysine complex as selector. J Chromatogr A 2002; 945:249-55. [PMID: 11860139 DOI: 10.1016/s0021-9673(01)01494-7] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A ligand-exchange capillary electrophoretic method was explored, with L-lysine as the ligand and copper(II) as the central ion. Its applicability was demonstrated with underivatized aromatic amino acids, namely D,L-phenylalanine, D,L-tryptophan, D,L-tyrosine and D,L-beta-phenylserine. Optical resolutions of a single pair of amino acid enantiomers, and of mixed amino acids were obtained with a running buffer of 10 mM NH4Ac, 6.67 mM Cu(II) and 13.33 mM L-lysine, pH 7.0. Sodium dodecylsulfate (SDS) was shown to be necessary for simultaneous separation of the mixed amino acids. The resolution was found to increase with the concentration of the copper(II) complex at a copper(II)-to-lysine ratio of 1:2. If the total concentration of copper(II) and lysine was kept at 20 mM, decreasing the ratio of copper(II) to lysine caused a resolution loss of tryptophan, but a slight resolution improvement of the other three amino acids. The pH of buffer is another important factor controlling the separations. For all the studied amino acids, the optimum pH was 6.0. An interesting phenomenon was observed in this study. SDS induces precipitation at a concentration below 32 mM at room temperature (16+/-2 degrees C), possibly due to the formation of neutral substance from the SDS monomer and the copper(II)-lysine complex.
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Affiliation(s)
- Xiaoning Lu
- Center for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing
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24
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Chen Z, Uchiyama K, Hobo T. Chemically modified chiral monolithic silica column prepared by a sol-gel process for enantiomeric separation by micro high-performance liquid chromatography. J Chromatogr A 2002; 942:83-91. [PMID: 11822400 DOI: 10.1016/s0021-9673(01)01381-4] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In this work a new type of chiral monolith silica column was developed for the chiral separation by micro high-performance liquid chromatography (micro-HPLC). The chiral monolith column with a continuous skeleton and a large through-pore structure was prepared inside a capillary of 100 microm I.D. by a sol-gel process, and chemically modified with chiral selectors, such as L-phenylalaninamide, L-alaninamide and L-prolinamide, on the surface of the monolithic silica column. Based on the principle of ligand exchange, these chiral monolithic columns were successfully used for the separation of dansyl amino acid enantiomers, as well as hydroxy acid enantiomers by micro-HPLC. The chromatographic conditions, the enantioselectivity and the performance of columns are discussed.
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Affiliation(s)
- Zilin Chen
- Department of Applied Chemistry, Graduate School of Engineering, Tokyo Metropolitan University, Hachioji, Japan.
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25
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Chen Z, Yamada K, Niitsuma M, Uchiyama K, Hobo T. Separation selectivity in micellar electrokinetic chromatography using different anionic surfactants as pseudo-stationary phases. Chromatographia 2001. [DOI: 10.1007/bf02492190] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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26
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Chen Z, Hobo T. Chemically L-prolinamide-modified monolithic silica column for enantiomeric separation of dansyl amino acids and hydroxy acids by capillary electrochromatography and mu-high performance liquid chromatography. Electrophoresis 2001; 22:3339-46. [PMID: 11589299 DOI: 10.1002/1522-2683(200109)22:15<3339::aid-elps3339>3.0.co;2-5] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A silica-based chiral monolithic column prepared by sol-gel process and chemical modification of chiral selector was used for enantioseparation of dansyl amino acids and hydroxy acids by capillary electrochromatography (CEC) and mu-high-performance liquid chromatography (mu-HPLC). L-Prolinamide was modified as a chiral selector. The chiral stationary phase (CSP), the chiral complex of Cu(II) with L-prolinamide, provides an anodic electroosmotic flow (EOF) in CEC. The EOF was found to be dependent on applied electric field strength, the pH, and the composition of mobile phases. Scanning electron micrograph showed that monolithic columns have the morphology of continuous skeleton and large through-pore. D-Enantiomers migrated before L-enantiomers except for dansyl-(Dns)-DL-Ser. The separation efficiencies of up to 17600 (D) and 13,200 plates m(-1) (L) were achieved for the separation of DL-indole-3-lactic acid.
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Affiliation(s)
- Z Chen
- Department of Applied Chemistry, Graduate School of Engineering, Tokyo Metropolitan University, Japan.
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Schmid MG, Grobuschek N, Lecnik O, Gübitz G. Chiral ligand-exchange capillary electrophoresis. ACTA ACUST UNITED AC 2001; 48:143-54. [PMID: 11356484 DOI: 10.1016/s0165-022x(01)00145-2] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
This review summarizes the application of capillary electrophoresis and capillary electrochromatography for the chiral separation of various substance classes using the principle of ligand exchange. The application of this principle to various substance classes is reported.
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Affiliation(s)
- M G Schmid
- Institute of Pharmaceutical Chemistry, Karl-Franzens University, Universitätsplatz 1, A-8010, Graz, Austria
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28
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Chen Z, Uchiyama K, Hobo T. Interaction between 18-crown-6-tetracarboxylic acid and positional substituents of enantiomers and simultaneous separation of positional enantiomers of methyl-DL-tryptophans by capillary electrophoresis. Electrophoresis 2001; 22:2136-42. [PMID: 11504044 DOI: 10.1002/1522-2683(20017)22:11<2136::aid-elps2136>3.0.co;2-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
18-Crown-6-tetracarboxylic acid (18C6H4) is a chiral selector with high selectivity for the enantioseparation of solutes bearing the primary amine function. This work presents the simultaneous separation of positional enantiomers of methyl-DL-tryptophans by using 18C6H4 as an additive to the background electrolyte. Separation conditions such as pH, the concentration of 18C6H4, and the applied voltages have critical inference on the simultaneous separation. The addition of cyclodextrins as anionic surfactants to the background electrolyte did not improve the separation. The selector-selectand interactions between 18C6H4 and the positional enantiomers have been investigated. It was observed that both the position and type of substituents contribute to the enantioselectivity. The migration order and resolution depended on the distance from the substituents to the asymmetric carbon of the enantiomers.
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Affiliation(s)
- Z Chen
- Department of Applied Chemistry, Graduate School of Engineering, Tokyo Metropolitan University, Japan.
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29
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Other chiral selectors. Chromatographia 2001. [DOI: 10.1007/bf02492895] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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30
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Abstract
This review summarizes recent developments in the field of chiral separations by electromigration techniques including capillary zone electrophoresis (CZE), capillary gel electrophoresis (CGE), isotachophoresis (ITP), electrokinetic chromatography (EKC), and capillary electrochromatography (CEC). This overview focuses on the development of new chiral selectors and the introduction of new techniques rather than applications of already established selectors and methods. The mechanisms of the different chiral separation principles are discussed.
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Affiliation(s)
- G Gübitz
- Institute of Pharmaceutical Chemistry, Karl-Franzens University, Graz, Austria.
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31
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Abstract
Chiral separation of amino acids and peptides by capillary electrophoresis (CE) is reviewed regarding the separation principles of different approaches, advantages and limitations, chiral recognition mechanisms and applications. The direct approach details various chiral selectors with an emphasis on cyclodextrins and their derivatives, antibiotics and chiral surfactants as the chiral selectors. The indirect approach deals with various chiral reagents applied for diastereomer formation and types of separation media such as micelles and polymeric pseudo-stationary phases. Many derivatization reagents used for high sensitivity detection of amino acids and peptides are also discussed and their characteristics are summarized in tables. A large number of relevant examples is presented illustrating the current status of enantiomeric and diastereomeric separation of amino acids and peptides. Strategies to enhance the selectivity and optimize separation parameters by the application of experimental designs are described. The reversal of enantiomeric elution order and the effects of organic modifiers on the selectivity are illustrated in both direct and indirect methods. Some applications of chiral amino acid and peptide analysis, in particular, regarding the determination of trace enantiomeric impurities, are given. This review selects more than 200 articles published between 1988 and 1999.
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Affiliation(s)
- H Wan
- Department of Chemistry, Karlstad University, Sweden
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32
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Schmid MG, Lecnik O, Sitte U, Gübitz G. Application of ligand-exchange capillary electrophoresis to the chiral separation of alpha-hydroxy acids and beta-blockers. J Chromatogr A 2000; 875:307-14. [PMID: 10839150 DOI: 10.1016/s0021-9673(99)01333-3] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The application of the principle of ligand-exchange capillary electrophoresis to two substance classes is described. As chiral selector N-(2-hydroxyoctyl)-L-4-hydroxyproline-copper(II) complex was used. This principle was applied to the chiral separation of alpha-hydroxy acids and drugs containing amino alcohol structure such as beta-blockers. The enantioselectivity was found to be strongly dependent on pH corresponding to the optimal conditions for complex formation for each structure class.
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Affiliation(s)
- M G Schmid
- Institute of Pharmaceutical Chemistry, Karl-Franzens University, Graz, Austria
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33
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CHEN Z, LIN J, UCHIYAMA K, HOBO T. Reversal Behaviors of the Enantiomer Migration Order and the Stereo-selectivity of Cu(II) Complex with Amino Acid Enantiomers in Ligand Exchange-Micellar Electrokinetic Chromatography. ANAL SCI 2000. [DOI: 10.2116/analsci.16.131] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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34
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CHEN Z, UCHIYAMA K, HOBO T. Estimation of Formation Constants of Ternary Cu(II) Complexes with Mixed Amino Acid Enantiomers Based on Ligand Exchange by Capillary Electrophoresis. ANAL SCI 2000. [DOI: 10.2116/analsci.16.837] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Zilin CHEN
- Department of Applied Chemistry, Graduate School of Engineering, Tokyo Metropolitan University
| | - Katsumi UCHIYAMA
- Department of Applied Chemistry, Graduate School of Engineering, Tokyo Metropolitan University
| | - Toshiyuki HOBO
- Department of Applied Chemistry, Graduate School of Engineering, Tokyo Metropolitan University
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35
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Chen Z, Lin JM, Uchiyama K, Hobo T. Determination of critical micelle concentrations of anionic surfactants based on ligand exchange micellar electrokinetic chromatography. Anal Chim Acta 2000. [DOI: 10.1016/s0003-2670(99)00565-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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36
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CHEN Z, UCHIYAMA K, HOBO T. Separation of hydroxy acid enantiomers by ligand exchange-micellar electrokinetic chromatography. BUNSEKI KAGAKU 2000. [DOI: 10.2116/bunsekikagaku.49.759] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Zilin CHEN
- Department of Applied Chemistry,Graduate School of Engineering,Tokyo Metropolitan University,1-1,Minamiosawa,Hachioji-shi,Tokyo 192-0397
| | - Katsumi UCHIYAMA
- Department of Applied Chemistry,Graduate School of Engineering,Tokyo Metropolitan University,1-1,Minamiosawa,Hachioji-shi,Tokyo 192-0397
| | - Toshiyuki HOBO
- Department of Applied Chemistry,Graduate School of Engineering,Tokyo Metropolitan University,1-1,Minamiosawa,Hachioji-shi,Tokyo 192-0397
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