Non-aqueous capillary electrophoresis chiral separations with sulfated beta-cyclodextrin

This paper reports the application of an anionic cyclodextrin (CD), sulfate d beta-cyclodextrin with a degree of substitution of four (beta-CD-(SO4-)(4 ), in chiral separations of pharmaceutical enantiomers by non-aqueous capil lary electrophoresis (NACE). Upon complexation with the anionic CD, electro phoretic mobilities of the basic enantiomers decreased, however, both separ ation selectivity and resolution were enhanced. The advantage of NACE: chir al separations over the aqueous CE the charged CD is that higher electric f ield strength and higher ionic strength could be applied due to the charact eristics the solvent formamide. The higher ionic strength leads to stacking of peaks and reduces the electrodispersion caused by mobility mismatch bet ween beta-CD-(SO4-)(4)-analyte complexes and the co-ions in the running buf fer. As a result, better shapes and higher separation efficiency were obtai ned. Comparing with NACE chiral separations with neutral CDs, lower concent ration of beta-CD-(SO4-)(4)was needed due to the fact that the electrostati c attraction caused stronger binding between beta-CD-(SO4-)(4) and the enan tiomers. The effects of the experimental parameters, such as concentration of the CD, apparent pH (pH*), degree of substitutions of the CDs, percentag e of water in mixed solvent systems, and type of solvents were also studied . (C) 1999 Elsevier Science B.V. All rights reserved.