Extending the scope of chiral separation of basic compounds by cyclodextrin-mediated capillary zone electrophoresis

Abstract

In a previous paper on cyclodextrin-mediated capillary zone electrophoresis, it was shown that the use of short-chain tetraalkylammonium cations leads to a reversal in the direction of the electroosmotic flow without an adverse effect on enantioselectivity. As a result, enantiomeric resolution of basic (cationic) compounds can be improved as the electroosmotic flow counteracts the migration of solute enantiomers. It is demonstrated in this report that the scope of chiral separation of basic compounds can be further extended by a combination of reversing the electroosmotic flow and enhancing enantioselectivity through the chemical modifications of β-cyclodextrin. Therefore, β-cyclodextrin and its derivatives were evaluated as chiral recognition agents for the chiral separations of 22 basic compounds with rather complex molecular structures. The differences in enantioselectivity displayed by β-cyclodextrin and derivatives are discussed in order to achieve a better understanding of the chiral interactions involved in the discrimination of solute enantiomers.