Comparison of native, alkylated and charged cyclodextrins for the chiral separation of labetalol stereoisomers by capillary electrophoresis

A capillary electrophoresis method for the enantioresolution of labetalol w as developed using CDs as chiral selectors and uncoated capillaries. Variou s native (alpha-, beta- and gamma-CD), alkylated (hydroxy propyl-beta- and gamma-CD, methyl-beta-CD) and anionic (sulfated-beta-CD and sulfobutylether -gamma-CD) cyclodextrins were tested and operational parameters such as buf fer pH, concentration of CD were investigated. Propranolol was also studied as a model compound. Uncharged gamma-CDs were more effective than beta-CDs to separate the enantiomers of labetalol but no complete resolution of the four isomers was obtained. The use of charged cyclodextrins led to a combi nation of hydrophobic inclusion and ion-pairing interaction in the chiral r ecognition mechanism. Thus, a complete resolution of the four enantiomers o f the labetalol was attained using 7.7 g/l sulfated-beta-CD in a 30 mM phos phate buffer, pH 6.5. (C) 1998 Elsevier Science B.V. All rights reserved.