Enhancement of enantioselectivity in chiral capillary electrophoresis using hydroxypropyl-beta-cyclodextrin as chiral selector under molecular crowding conditions induced by dextran or dextrin.

Abstract

Molecular crowding is a new approach to enhance the retention properties and selectivity of molecularly imprinted polymers. In this work, this concept was first applied to chiral CE to enhance its enantioselectivity. A model system, enantioseparation of salbutamol using hydroxypropyl-beta-cyclodextrin as chiral selector in the presence of dextran or dextrin as crowding-inducing agents, was chosen to demonstrate its potency. Some parameters, especially the concentration of crowding-inducing agents and cyclodextrins were investigated intensively. Moreover, based on fluorescence spectroscopy and affinity CE, it was found that the presence of crowding-inducing agents could promote the association of enantiomers with cyclodextrins and intensify the interacting differences of two enantiomers with cyclodextrins. As a result, the essential concentration of cyclodextrins to make the enantiomers reach baseline separation was significantly decreased with the aid of molecular crowding. This study shows that molecular crowding is an effective strategy to enhance the enantioselectivity of cyclodextrin in chiral CE.