Capillary Electrophoretic Resolution of Chiral Aryl Alkyl and Aryl Benzyl Sulphoxides Using Sulphated b-Cyclodextrins as Chiral Selectors

The enantiomeric resolution of a series of chiral aryl alkyl and aryl benzyl sulphoxides was investigated by reversed-polarity capillary electrophoresis using sulphated-β-cyclodextrins as chiral selectors. Separations were performed using fused silica capillaries with a lithium phosphate run buffer (100 mM, pH 2) containing hydroxylethylcellulose as a dynamic coating agent to virtually eliminate electroosmotic flow and sulphated-β-cyclodextrins as chiral selectors. The majority of enantiomeric pairs were resolved in the presence of heptakis-6-sulphato-β-cyclodextrin, heptakis-(2,3-diacetyl-6-sulphato)-β-cyclodextrin, and sulphated-β-cyclodextrin (average degree of substitution = 4). In general, the electrophoretic migration order was R- before S-sulphoxide, indicating generally greater affinities between the R-enantiomers and the sulphated β-CDs.