Potential and limitations of an optically active crown ether for chiral separation in capillary zone electrophoresis

Kuhn, Reinhard; Wagner, Joseph; Walbroehl, Yvonne; Bereuter, Thomas

doi:10.1002/elps.11501501117

Cited by 79 publications

(34 citation statements)

References 26 publications

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“…As a result, we achieved the enantiomeric separation of racemic terbutaline shown in Fig. 3 (separation factor 13 , α=1.03; resolution, Rs=1.21; theoretical plate number, N > =26000). We also obtained the enantiomeric separation of racemic benzoin (Fig 1, b), as shown in Fig.…”

Section: Resultsmentioning

confidence: 90%

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Enantiomeric Separations of Cationic and Neutral Compounds by Capillary Electrochromatography with Charged Polyacrylamide Gels Incorporating Chiral Selectors

Koide

Ueno

1998

ANAL. SCI.

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Section: Resultsmentioning

confidence: 90%

“…We presumed that polymeric β-CDs would not be eluted by EOF because of their large molecular weight (Table 1). However, the resolution 13 decreased when the analysis was repeated ten times for about 4 h (Fig. 2, b).…”

Section: Resultsmentioning

confidence: 99%

Enantiomeric Separations of Cationic and Neutral Compounds by Capillary Electrochromatography with Charged Polyacrylamide Gels Incorporating Chiral Selectors

Koide

Ueno

1998

ANAL. SCI.

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“…3 792 ANALYTICAL SCIENCES AUGUST 1999, VOL. 15 (a: separation factor 14 , α=1.05; resolution 14 , R s =1.86; theoretical plate number, N 67000 m -1 . b: α=1.03, R s =1.54, N 84000 m -1 ).…”

Section: Resultsmentioning

confidence: 99%

Enantiomeric Separations of Cationic and Neutral Compounds by Capillary Electrochromatography with β-Cyclodextrin-Bonded Charged Polyacrylamide Gels

Koide¹,

Ueno²

1999

ANAL. SCI.

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Enantiomeric separation is one of the most important research themes in analytical chemistry, especially in the pharmaceutical field. A large number of drugs, which have one or more asymmetric centers, exist as a couple of enantiomers. Since the pharmacological activity and metabolism of two enantiomers of a certain drug may very often differ, enantioselective analytical methods are required for chiral purity control, pharmacokinetic studies and other work. During the last decade, tremendous efforts have been expended to develop enantiomeric separation methods. Important advances have been achieved with HPLC, gas chromatography and capillary electrophoresis (CE). In particular, CE is attractive because of its advantages of high efficiency, relatively short analysis time and minimal sample volume requirement.Capillary electrochromatography (CEC), which is in essence a hybrid of HPLC and CE and is based on a fascinating new chromatographic concept 1 , has become increasingly popular. CEC is a powerful separation method which affords a higher theoretical plate number and superior efficiency due to its flat flow profile, compared with micro-HPLC which uses the same packing material. The separation mechanism of neutral compounds in CEC is the same as that of HPLC in principle, with separations essentially resulting from differences in the partitioning of solutes between a mobile phase and a stationary phase.Currently, capillaries packed with the typical stationary phase for HPLC are still used in the majority of CEC studies. However, monolithic stationary phases 2-8 , which are ungranular polymeric separation media, are increasingly gaining attention due to their simple preparation method, wide varieties of functionalization and better stability. Very recently, the enantiomeric separation of N-(3,5-dinitrobenzoyl)leucine diallylamide was obtained using monolithic chiral stationary phases for CEC prepared within the confines of untreated fused-silica capillaries by the direct copolymerization of the chiral monomer 2-hydroxyethyl methacrylate (N-L-valine-3,5-dimethylanilide) carbamate with ethylene dimethacrylate, 2-acrylamido-2-methylpropanesulfonic acid and butyl or glycidyl methacrylate in the presence of a porogenic solvent. 9 In our previous paper 10 , the enantiomeric separations of cationic and neutral compounds by CEC using a charged polyacrylamide gel as a monolithic stationary phase, in which polymeric β-cyclodextrins (β-CD) as chiral selectors are immobilized by incorporation, were reported. Unfortunately, no enantiomeric separation was achieved using monomeric β-CD, because it was eluted out of the capillary column by electroosmotic flow (EOF) to the cathodic solution during preelectrophoresis.In this paper, successful enantiomeric separations of cationic and neutral compounds by CEC using charged polyacrylamide gels to which allyl carbamoylated β-CD derivatives (AC-β -CD) covalently bind as monomeric β-CD are reported. ExperimentalApparatus CEC experiments were carried out at room temperature (approximatel...

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“…[1][2][3][4][5][6][7] The host-guest complexation mechanisms for the chiral recognition of crown ethers toward chiral amines have been well established. 2,6 The accurate chiral discrimination of each separated analyte has become an important task for their optical purity control and stereoselective pharmacokinetic studies in chiral drug development.…”

mentioning

confidence: 99%

Chiral Discrimination of Aromatic Amino Acids by Capillary Electrophoresis in (+)- and (-)-(18-Crown-6)-2,3,11,12-tetracarboxylic Acid Selector Modes

2003

Bulletin of the Korean Chemical Society

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Optically active (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid (18C6H 4 ) ( Figure 1) has been successfully employed as a chiral selector in enantioseparations of diverse amino acids and chiral primary amines in capillary electrophoresis (CE). 1-7The host-guest complexation mechanisms for the chiral recognition of crown ethers toward chiral amines have been well established. 2,6 The accurate chiral discrimination of each separated analyte has become an important task for their optical purity control and stereoselective pharmacokinetic studies in chiral drug development. The migration order of separated enantiomers is mainly determined by co-electrophoresis with enantiomerically pure standards and matching its migration time or relative migration time (RMT) with that of the reference. However, crosschecking two RMT sets measured with two chiral selectors of different enantioselectivities could enhance confidence in the identification of CE peaks and the chiral discrimination as well. Based on this concept, simultaneous chiral discrimination of 15 racemic aromatic amino acids was achieved with chiral CE in neutral and charged cyclodextrin modes in our previous report. 8 The surest way of the accurate chiral discrimination is the reversal of enantiomer migration order (EMO).9-16 It is especially desirable when peak tailing, fronting or overlapping is observed. Among the diverse ways of EMO reversal developed, suppressing or reversing the direction of electroosmotic flow has been most widely used. 9,[12][13][14][15][16] In our recent report, simultaneous EMO reversal of nine chiral profens was achieved in the normal polarity and reversed polarity modes. 16 The most certain and easy method of EMO reversal might be, however, the use of two chiral selectors with the opposite chiral recognition ability, like (+)-18C6H 4 and (−)-18C6H 4 when employing crown ether-modified CE systems. However, no attempt to exploit the crosschecking each EMO measured in these two selector modes has been made in chiral CE of amino acids to date. The present study was undertaken to investigate EMO reversal by crown ether modified-CE system in the two selector modes with (+)-18C6H 4 and (−)-18C6H 4 for the chiral discrimination of nine aromatic amino acids. When (+)-18C6H 4 was added at 5 mM to 20 mM Triscitric acid buffer (pH 2.50), each enantiomeric pairs of nine aromatic amino acids studied were baseline-resolved with similar enantioselectivity and resolution factor except for 3-hydroxyphenylglycine (Table 1). 3-Hydroxyphenylglycine showed much stronger interaction with the selector than other analytes, thereby yielding a very large separation factor (1.684) and resolution factor (21.99). In good agreement with the previous reports, 1,2,4 each D-enantiomer migrated slower than the corresponding L-isomer, indicating that the D-isomers were bound more strongly with (+)-18C6H 4 in CE. The (R)-baclofen migrated ahead of the (S)-enantiomer. When (+)-18C6H 4 was replaced in the same buffer condition with its antipode, (−)-18C6H 4 (Figure 1), ...

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Potential and limitations of an optically active crown ether for chiral separation in capillary zone electrophoresis

Cited by 79 publications

References 26 publications

Enantiomeric Separations of Cationic and Neutral Compounds by Capillary Electrochromatography with Charged Polyacrylamide Gels Incorporating Chiral Selectors

Enantiomeric Separations of Cationic and Neutral Compounds by Capillary Electrochromatography with Charged Polyacrylamide Gels Incorporating Chiral Selectors

Enantiomeric Separations of Cationic and Neutral Compounds by Capillary Electrochromatography with β-Cyclodextrin-Bonded Charged Polyacrylamide Gels

Chiral Discrimination of Aromatic Amino Acids by Capillary Electrophoresis in (+)- and (-)-(18-Crown-6)-2,3,11,12-tetracarboxylic Acid Selector Modes

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