Study on the chiral separation of basic drugs by capillary zone electrophoresis using β-CD and derivatized β-CDs as chiral selectors

Capillary zone electrophoresis was used for the enantiomeric separation of racemic ketamine, anisodamine and isoprenaline with β-cyclodextrin (β-CD) and β-cyclodextrin derivatives as chiral selectors employing an uncoated capillary. The β-CD types and concentrations have strong influence on the efficiency of the chiral separation. The effects of the pH and composition of the background electrolyte (BGE), the amphiphilic compound in the BGE and the capillary temperature on the mobility and chiral separation have been studied. 2,6-di-O-carboxymethyl-β-cyclodextrin (CM-β-CD) gave a baseline enantiomeric separation for the basic drugs under study, whereas the β-CD and its glutamic acid derivative, under the same experimental conditions, were poor in stereoselectivity and gave just partial chiral separation. Moreover, the acetic diamine derivative, gelatin derivative and phosphate ester derivative showed no chiral recognition. The tetraethylammonium bromide and tetrabutylammoniun bromide added to the BGE could improve the chiral separation but the hexadecyltrimethylammonium bromide made the chiral separation worse while using β-CD as chiral selector. Lower capillary temperatures were more favorable for the chiral resolution.