1
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Single isomer cyclodextrins as chiral selectors in capillary electrophoresis. J Chromatogr A 2020; 1627:461375. [PMID: 32823120 DOI: 10.1016/j.chroma.2020.461375] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Revised: 06/24/2020] [Accepted: 06/28/2020] [Indexed: 12/23/2022]
Abstract
Since decades, cyclodextrins are one of the most powerful selectors in chiral capillary electrophoresis for the enantioseparation of diverse organic compounds. This review concerns papers published over the last decade (from 2009 until nowadays), dealing with the capillary electrophoretic application of single isomer cyclodextrin derivatives in chiral separations. Following a brief overview of their synthetic approaches, the inventory of the neutral, negatively and positively charged (including both permanently ionic and pH-tunable ionizable substituents) and zwitterionic CD derivatives is presented, with insights to underlying structural aspects by NMR spectroscopy and molecular modeling. CE represents an ideal tool to study the weak, non-covalent supramolecular interactions. The published methods are reviewed in the light of enantioselectivity, enantiomer migration order and the fine-tuning of enantiodiscrimination by the substitution pattern of the single entity selector molecules, which is hardly possible for their randomly substituted counterparts. All the reviewed publications herein support that cyclodextrin-based chiral capillary electrophoresis seems to remain a popular choice in pharmaceutical and biomedical analysis.
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2
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Pires BC, Coelho JF, Silva CF, Dutra FV, Guimarães L, Nascimento CS, Borges KB. Enantioselective separation of bupropion and its major metabolite hydroxybupropion: An experimental and theoretical study. Chem Phys Lett 2019. [DOI: 10.1016/j.cplett.2019.05.035] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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3
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Fanali S, Chankvetadze B. Some thoughts about enantioseparations in capillary electrophoresis. Electrophoresis 2019; 40:2420-2437. [PMID: 31081552 DOI: 10.1002/elps.201900144] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Revised: 04/22/2019] [Accepted: 04/23/2019] [Indexed: 12/20/2022]
Abstract
In this overview the goal of the authors was to analyze from the historical perspective the reasons of success and failure of chiral capillary electrophoresis. In addition, the current trends are analyzed, unique advantages of capillary electrophoresis are highlighted and some future directions are discussed.
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Affiliation(s)
- Salvatore Fanali
- School in Natural Science and Engineering, University of Verona, Verona, Italy
| | - Bezhan Chankvetadze
- Institute of Physical and Analytical Chemistry, School of Exact and Natural Sciences, Tbilisi State University, Tbilisi, Georgia
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4
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Servais AC, Fillet M. Enantioseparations in Nonaqueous Capillary Electrophoresis Using Charged Cyclodextrins. Methods Mol Biol 2019; 1985:373-381. [PMID: 31069746 DOI: 10.1007/978-1-4939-9438-0_21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The enantioseparation of acidic and basic compounds can be successfully achieved in nonaqueous capillary electrophoresis (NACE) using single-isomer charged β-cyclodextrin (β-CD) derivatives of opposite charge to that of the analytes. This chapter describes how to separate the enantiomers of three basic substances selected as model compounds, i.e., alprenolol, bupranolol, and terbutaline, using the negatively charged heptakis(2,3-di-O-acetyl-6-O-sulfo)-β-CD (HDAS-β-CD). The enantiomers of three acidic drugs (tiaprofenic acid, suprofen, and flurbiprofen) are resolved using a monosubstituted amino β-CD derivative, namely 6-monodeoxy-6-mono(3-hydroxy)propylamino-β-CD (PA-β-CD).
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Affiliation(s)
- Anne-Catherine Servais
- Laboratory for the Analysis of Medicines, Department of Pharmaceutical Sciences, CIRM, Quartier Hôpital, University of Liège, Liège, Belgium.
| | - Marianne Fillet
- Laboratory for the Analysis of Medicines, Department of Pharmaceutical Sciences, CIRM, Quartier Hôpital, University of Liège, Liège, Belgium
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5
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Fejős I, Varga E, Benkovics G, Darcsi A, Malanga M, Fenyvesi É, Sohajda T, Szente L, Béni S. Comparative evaluation of the chiral recognition potential of single-isomer sulfated beta-cyclodextrin synthesis intermediates in non-aqueous capillary electrophoresis. J Chromatogr A 2016; 1467:454-462. [DOI: 10.1016/j.chroma.2016.07.033] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Revised: 07/08/2016] [Accepted: 07/14/2016] [Indexed: 10/21/2022]
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6
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Řezanka P, Řezanková K, Sedláčková H, Mašek J, Rokosová L, Bláhová M, Řezanka M, Jindřich J, Sýkora D, Král V. Influence of substituent position and cavity size of the regioisomers of monocarboxymethyl-α-, β-, and γ-cyclodextrins on the apparent stability constants of their complexes with both enantiomers of Tröger's base. J Sep Sci 2016; 39:980-5. [DOI: 10.1002/jssc.201500845] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Revised: 12/03/2015] [Accepted: 12/12/2015] [Indexed: 11/06/2022]
Affiliation(s)
- Pavel Řezanka
- Department of Analytical Chemistry; University of Chemistry and Technology; Prague Czech Republic
| | - Klára Řezanková
- Department of Analytical Chemistry; University of Chemistry and Technology; Prague Czech Republic
| | - Helena Sedláčková
- Department of Analytical Chemistry; University of Chemistry and Technology; Prague Czech Republic
| | - Jindřich Mašek
- Department of Analytical Chemistry; University of Chemistry and Technology; Prague Czech Republic
| | - Lenka Rokosová
- Department of Analytical Chemistry; University of Chemistry and Technology; Prague Czech Republic
| | - Markéta Bláhová
- Department of Organic Chemistry, Faculty of Science; Charles University in Prague; Prague 2 Czech Republic
| | - Michal Řezanka
- Institute for Nanomaterials, Advanced Technologies and Innovation; Technical University of Liberec; Liberec 1 Czech Republic
| | - Jindřich Jindřich
- Department of Organic Chemistry, Faculty of Science; Charles University in Prague; Prague 2 Czech Republic
| | - David Sýkora
- Department of Analytical Chemistry; University of Chemistry and Technology; Prague Czech Republic
| | - Vladimír Král
- Department of Analytical Chemistry; University of Chemistry and Technology; Prague Czech Republic
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7
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Mavridis IM, Yannakopoulou K. Anionic cyclodextrins as versatile hosts for pharmaceutical nanotechnology: Synthesis, drug delivery, enantioselectivity, contrast agents for MRI. Int J Pharm 2015; 492:275-90. [DOI: 10.1016/j.ijpharm.2015.06.004] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Revised: 06/03/2015] [Accepted: 06/04/2015] [Indexed: 12/30/2022]
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8
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Wang Y, Zhou J, Liu Y, Tang J, Tang W. Evaluation of the chiral separation ability of single-isomer cationic β-cyclodextrins in capillary electrophoresis. Electrophoresis 2014; 35:2744-51. [DOI: 10.1002/elps.201400198] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Revised: 06/22/2014] [Accepted: 06/22/2014] [Indexed: 11/07/2022]
Affiliation(s)
- Yiying Wang
- Key Laboratory of Soft Chemistry and Functional Materials (Ministry of Education of China); Nanjing University of Science and Technology; Nanjing P. R. China
| | - Jie Zhou
- Key Laboratory of Soft Chemistry and Functional Materials (Ministry of Education of China); Nanjing University of Science and Technology; Nanjing P. R. China
| | - Yun Liu
- Key Laboratory of Soft Chemistry and Functional Materials (Ministry of Education of China); Nanjing University of Science and Technology; Nanjing P. R. China
| | - Jian Tang
- Key Laboratory of Soft Chemistry and Functional Materials (Ministry of Education of China); Nanjing University of Science and Technology; Nanjing P. R. China
| | - Weihua Tang
- Key Laboratory of Soft Chemistry and Functional Materials (Ministry of Education of China); Nanjing University of Science and Technology; Nanjing P. R. China
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9
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Řezanka P, Navrátilová K, Řezanka M, Král V, Sýkora D. Application of cyclodextrins in chiral capillary electrophoresis. Electrophoresis 2014; 35:2701-21. [DOI: 10.1002/elps.201400145] [Citation(s) in RCA: 123] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2014] [Revised: 05/14/2014] [Accepted: 05/19/2014] [Indexed: 12/13/2022]
Affiliation(s)
- Pavel Řezanka
- Department of Analytical Chemistry; Institute of Chemical Technology; Prague Czech Republic
| | - Klára Navrátilová
- Department of Analytical Chemistry; Institute of Chemical Technology; Prague Czech Republic
| | - Michal Řezanka
- Institute for Nanomaterials; Advanced Technologies and Innovation; Technical University of Liberec; Liberec Czech Republic
| | - Vladimír Král
- Department of Analytical Chemistry; Institute of Chemical Technology; Prague Czech Republic
| | - David Sýkora
- Department of Analytical Chemistry; Institute of Chemical Technology; Prague Czech Republic
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10
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Servais AC, Fillet M. Enantioseparations in nonaqueous capillary electrophoresis using charged cyclodextrins. Methods Mol Biol 2013; 970:297-305. [PMID: 23283786 DOI: 10.1007/978-1-62703-263-6_19] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The enantioseparation of acidic and basic compounds can be successfully achieved in nonaqueous capillary electrophoresis using single-isomer charged β-cyclodextrin (β-CD) derivatives of opposite charge to that of the analytes. This chapter describes how to separate the enantiomers of three basic substances selected as model compounds, i.e., alprenolol, bupranolol, and terbutaline, using the negatively charged heptakis(2,3-di-O-acetyl-6-O-sulfo)-β-CD. The enantiomers of three acidic drugs (tiaprofenic acid, suprofen, and flurbiprofen) are resolved using a monosubstituted amino β-CD derivative, namely, 6-monodeoxy-6-mono(3-hydroxy)propylamino-β-CD.
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11
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Řezanka M, Řezanka P, Sýkora D, Jindřich J, Král V. Impact of substituent position in monosubstituted α-cyclodextrins on enantioselectivity in capillary electrophoresis. J Sep Sci 2012; 35:811-5. [DOI: 10.1002/jssc.201101034] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Michal Řezanka
- Department of Organic and Nuclear Chemistry, Faculty of Science; Charles University in Prague; Prague Czech Republic
| | - Pavel Řezanka
- Institute of Chemical Technology; Department of Analytical Chemistry; Prague Czech Republic
| | - David Sýkora
- Institute of Chemical Technology; Department of Analytical Chemistry; Prague Czech Republic
| | - Jindřich Jindřich
- Department of Organic and Nuclear Chemistry, Faculty of Science; Charles University in Prague; Prague Czech Republic
| | - Vladimír Král
- Institute of Chemical Technology; Department of Analytical Chemistry; Prague Czech Republic
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12
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Castro-Puyana M, Lammers I, Buijs J, Gooijer C, Ariese F. Sensitized phosphorescence as detection method for the enantioseparation of bupropion by capillary electrophoresis. Electrophoresis 2010; 31:3928-36. [DOI: 10.1002/elps.201000352] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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13
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Application of charged single isomer derivatives of cyclodextrins in capillary electrophoresis for chiral analysis. J Chromatogr A 2010; 1217:953-67. [DOI: 10.1016/j.chroma.2009.11.094] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2009] [Revised: 11/30/2009] [Accepted: 11/30/2009] [Indexed: 11/19/2022]
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14
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Giuffrida A, León C, García-Cañas V, Cucinotta V, Cifuentes A. Modified cyclodextrins for fast and sensitive chiral-capillary electrophoresis-mass spectrometry. Electrophoresis 2009; 30:1734-42. [DOI: 10.1002/elps.200800333] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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15
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Riveros T, Hanrahan G, Muliadi S, Arceo J, Gomez FA. On-capillary derivatization using a hybrid artificial neural network-genetic algorithm approach. Analyst 2009; 134:2067-70. [DOI: 10.1039/b909143b] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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16
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Scriba GKEV. Cyclodextrins in capillary electrophoresis enantioseparations--recent developments and applications. J Sep Sci 2008; 31:1991-2011. [PMID: 18491357 DOI: 10.1002/jssc.200800095] [Citation(s) in RCA: 140] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Capillary EKC has been established as a versatile and robust CE method for the separation of enantiomers. Within the chiral selectors added to the BGE CDs continue as the most widely used selectors due to their structural variety and commercial availability. This is reflected in the large number of practical applications of CDs to analytical enantioseparations that have been reported between January 2006 and January 2008, the period of time covered by this review. Most of these applications cover aspects of life sciences such as drug analysis, bioanalysis, environmental analysis, or food analysis. Moreover, new CD derivatives have been developed in an attempt to achieve altered enantioselectivities and to further broaden the application range. Finally, efforts will be summarized that aim at an understanding of the molecular level of the chiral recognition between CDs and the analytes.
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Affiliation(s)
- Gerhard K E V Scriba
- Department of Pharmaceutical Chemistry, School of Pharmacy, Friedrich Schiller University, Philosophenweg 14, D-07743 Jena, Germany.
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17
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Chiral separation by capillary electromigration techniques. J Chromatogr A 2008; 1204:140-56. [DOI: 10.1016/j.chroma.2008.07.071] [Citation(s) in RCA: 208] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2008] [Revised: 06/27/2008] [Accepted: 07/08/2008] [Indexed: 11/19/2022]
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18
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Juvancz Z, Kendrovics RB, Iványi R, Szente L. The role of cyclodextrins in chiral capillary electrophoresis. Electrophoresis 2008; 29:1701-12. [PMID: 18421743 DOI: 10.1002/elps.200700657] [Citation(s) in RCA: 107] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The members of the enantiomeric pairs frequently show rather different biological effects, so their chiral selective synthesis, pharmacological studies and analysis are necessary. CE has unique advantages in chiral analysis. The most frequently used chiral selectors are CDs in this field. This paper gives a short view on the advantages on CE in direct chiral separations, emphasizing the role of CDs. The reason for the broad selectivity spectra of CDs is discussed in detail. The physical background of chiral selective separations is briefly shown in CE. Their interaction mechanisms are shortly defined. The general trend of their use is statistically evaluated. Most frequently used CDs and CD derivatives are characterized. Advantages of ionizable CDs and single-isomer derivatives are shown. The general trend of their use is established.
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Affiliation(s)
- Zoltán Juvancz
- Department of Environmental Engineering, Budapest Tech. Polytechnical Institution, Budapest, Hungary.
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19
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Montes RE, Gomez FA, Hanrahan G. Response surface examination of the relationship between experimental conditions and product distribution in electrophoretically mediated microanalysis. Electrophoresis 2008; 29:375-80. [PMID: 18081199 DOI: 10.1002/elps.200700196] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
This work presents the first known use of response surface methodology (RSM) in electrophoretically mediated microanalysis. This concept is demonstrated by examining the optimization of reaction conditions for the conversion of nicotinamide adenine dinucleotide to nicotinamide adenine dinucleotide, reduced form by glucose-6-phosphate dehydrogenase (G6PDH, EC 1.1.1.49) in the conversion of glucose-6-phosphate to 6-phosphogluconate. Experimental factors including voltage, enzyme concentration, and mixing time of reaction at the applied voltage were selected at three levels and tested in a Box-Behnken response surface design. Upon migration in a capillary under CE conditions, plugs of substrate and enzyme are injected separately in buffer and allowed to react at variable conditions. Extent of reaction and product ratios were subsequently determined by CE. The model predicted results are shown to be in good agreement (7.1% discrepancy difference) with experimental data. The use of chemometric RSM provides a direct relationship between electrophoretic conditions and product distribution of microscale reactions using CE, thereby offering a new and versatile approach to optimizing enzymatic experimental conditions.
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Affiliation(s)
- Ruth E Montes
- Department of Chemistry, California Lutheran University, Thousand Oaks, CA, USA
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20
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Mandrioli R, Raggi MA. Electrodriven methods for the enantioseparation of second-generation antidepressant drugs: An update. Electrophoresis 2008; 29:252-9. [DOI: 10.1002/elps.200700500] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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21
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Chankvetadze B. Enantioseparations by using capillary electrophoretic techniques. The story of 20 and a few more years. J Chromatogr A 2007; 1168:45-70; discussion 44. [PMID: 17765908 DOI: 10.1016/j.chroma.2007.08.008] [Citation(s) in RCA: 203] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2007] [Revised: 07/27/2007] [Accepted: 08/02/2007] [Indexed: 11/29/2022]
Abstract
This paper provides the author's insight on the past, present and future of performing enantioseparations using capillary electrophoretic (CE) techniques. These techniques are discussed from the historical point of view, as well as based on their potential as the separation techniques of today and the future. The overview covers mechanistic as well as practical aspects of CE techniques.
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Affiliation(s)
- Bezhan Chankvetadze
- Institute of Chemistry, School of Exact and Natural Sciences and Molecular Recognition and Separation Science Laboratory, Tbilisi State University, Chavchavadze Ave. 1, 0128 Tbilisi, Georgia.
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Kahle KA, Foley JP. Review of aqueous chiral electrokinetic chromatography (EKC) with an emphasis on chiral microemulsion EKC. Electrophoresis 2007; 28:2503-26. [PMID: 17657766 DOI: 10.1002/elps.200600808] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The separation of enantiomers using electrokinetic chromatography (EKC) with chiral microemulsions is comprehensively reviewed through December 1, 2006. Aqueous chiral EKC separations based on other pseudostationary phases such as micelles and vesicles or on other chiral selectors such as CDs, crown ethers, glycopeptides, ligand exchange moeities are also reviewed from both mechanistic and applications perspective for the period of January 2005 to December 1, 2006.
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Affiliation(s)
- Kimberly A Kahle
- Department of Chemistry, Drexel University, Philadelphia, PA 19104, USA
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Gübitz G, Schmid MG. Advances in chiral separation using capillary electromigration techniques. Electrophoresis 2007; 28:114-26. [PMID: 17136739 DOI: 10.1002/elps.200600411] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
This review gives an overview of recent developments in CZE, EKC, and CEC covering the literature since the year 2004. Since there appeared a special issue on applications, this review focuses on the progress in electromigration techniques and new methodological developments. New techniques, new chiral selectors as well as new chiral stationary phases for CEC are discussed.
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Affiliation(s)
- Gerald Gübitz
- Department of Pharmaceutical Chemistry, Institute of Pharmaceutical Sciences, Karl-Franzens-University, Graz, Austria.
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Hsieh YC, Whang CW. Analysis of ethambutol and methoxyphenamine by capillary electrophoresis with electrochemiluminescence detection. J Chromatogr A 2006; 1122:279-82. [PMID: 16797572 DOI: 10.1016/j.chroma.2006.05.078] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2006] [Revised: 05/23/2006] [Accepted: 05/29/2006] [Indexed: 11/19/2022]
Abstract
A capillary electrophoresis (CE) coupled with electrochemiluminescence (ECL) detection method for the analysis of ethambutol (EB) and methoxyphenamine (MP) has been investigated. Complete separation of EB and MP was achieved in 8 min using a background electrolyte of 20 mM sodium phosphate at pH 10.0 and a separation voltage of 9 kV. ECL detection was performed with an indium/tin oxide (ITO) working electrode biased at 1.4 V (versus a Pt wire reference) in a 200 mM sodium phosphate buffer (pH 8.0) containing 3.5 mM Ru(bpy)3(2+) (where bpy = 2,2'-bipyridyl). Linear correlation (r > or = 0.993) between ECL intensity and drug concentration was obtained in the range 2-50 ng/ml. The limits of detection (LODs) for EB and MP in water were 1.0 and 0.9 ng/ml, respectively. The relative standard deviation values on peak size (10 ng/ml level) and migration time for the two drugs were in the ranges 5-8 and 0.2-0.7% (n = 7), respectively. Applicability of the CE-ECL method to the analysis of human plasma spiked with EB and MP was examined. The LODs for EB and MP in plasma were 0.4 and 0.3 microg/ml, respectively.
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Affiliation(s)
- Yi-Chien Hsieh
- Department of Chemistry, Tunghai University, Taichung 407, Taiwan
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