Enantioseparation of thalidomide and its hydroxylated metabolites using capillary electrophoresis with various cyclodextrins and their combinations as chiral buffer additives

The separation of thalidomide (TD) and its hydroxylated metabolites includi ng their simultaneous enantioseparation was studied in capillary electropho resis (CE) using four different randomly substituted charged cyclodextrin ( CD) derivatives, the combinations of some of them with each other, and beta -CD. TD, as well as two metabolites recently found in incubations of human liver microsomes and human blood, 5-hydroxythalidomide (5-OH-TD) and one of the diastereomeric 5'-hydroxythalidomides (5'-OH-TD), are neutral compound s. Therefore, they were resolved using charged chiral selectors in CE. Two different separation modes (normal polarity and carrier mode) and two diffe rent capillaries (fused-silica and polyacrylamide-coated) were tested. Base d on the behavior of the individual CDs, their designed combinations were s elected in order to improve the separation selectivity and enantioselectivi ty. Under optimized conditions all three chiral compounds and their enantio mers were resolved simultaneously.