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 including their simultaneous enantioseparation was studied in capillary electrophoresis (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 compounds. Therefore, they were resolved using charged chiral selectors in CE. Two different separation modes (normal polarity and carrier mode) and two different capillaries (fused-silica and polyacrylamide-coated) were tested. Based on the behavior of the individual CDs, their designed combinations were selected in order to improve the separation selectivity and enantioselectivity. Under optimized conditions all three chiral compounds and their enantiomers were resolved simultaneously.