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Enantioseparations of hydrobenzoin and structurally related compounds in capillary zone electrophoresis using heptakis(2,3‐dihydroxy‐6‐ O ‐sulfo)‐β‐cyclodextrin as chiral selector and enantiomer migration reversal of hydrobenzoin with a dual cyclodextrin system in the presence of borate complexation
Author(s) -
Lin ChingErh,
Lin ShengLi,
Fang IJu,
Liao WeiSsu,
Chen ChiaChong
Publication year - 2004
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/elps.200405968
Subject(s) - benzoin , chemistry , enantiomer , capillary electrophoresis , cyclodextrin , boron , stereochemistry , medicinal chemistry , chromatography , organic chemistry
We investigated the enantioseparations of racemic hydrobenzoin, together with benzoin and benzoin methyl ether, in capillary electrophoresis (CE) using the single‐isomer heptakis(2,3‐dihydroxy‐6‐ O ‐sulfo)‐β‐cyclodextrin (SI‐S‐β‐CD) as a chiral selector in the presence and absence of borate complexation and enantiomer migration reversal of hydrobenzoin with a dual CD system consisting of SI‐S‐β‐CD and β‐CD in the presence of borate complexation at pH 9.0 in a borate buffer. The enantioselectivity of hydrobenzoin increased remarkably with increasing SI‐S‐β‐CD concentration and the enantioseparation depended on CD complexation between hydrobenzoin‐borate and SI‐S‐β‐CD. The ( S , S )‐enantiomer of hydrobenzoin‐borate complexes interacted more strongly than the ( R , R )‐enantiomer with SI‐S‐β‐CD. The enantiomers of hydrobenzoin could be baseline‐resolved in the presence of SI‐S‐β‐CD at a concentration as low as 0.1% w/v, whereas the three test analytes were simultaneously enantioseparated with addition of 0.3% w/v SI‐S‐β‐CD or at concentrations >2.0% w/v in a borate buffer and 0.5% w/v in a phosphate background electrolyte at pH 9.0. Compared with the results obtained previously using randomly sulfated β‐CD (MI‐S‐β‐CD) in a borate buffer, enantioseparation of these three benzoin compounds is more advantageously aided by SI‐S‐β‐CD as the chiral selector. The enantioselectivity of hydrobenzoin depended greatly on the degree of substitution of sulfated β‐CD. Moreover, binding constants of the enantiomers of benzoin compounds to SI‐S‐β‐CD and those of hydrobenzoin‐borate complexes to SI‐S‐β‐CD were evaluated for a better understanding of the role of CD complexation in the enantioseparation and chiral recognition. Enantiomer migration reversal of hydrobenzoin could be observed by varying the concentration of β‐CD, while keeping SI‐S‐β‐CD at a relatively low concentration. SI‐S‐β‐CD and β‐CD showed the same chiral recognition pattern but they exhibited opposite effects on the mobility of the enantiomers.