Enantiomer separation of drugs by capillary electrophoresis using mixturesof beta-cyclodextrin sulfate and neutral cyclodextrins

Direct separation of enantiomers of drugs was investigated by capillary ele ctrophoresis employing mixtures of charged cyclodextrin derivatives (CDs) a nd electrically neutral CDs (i.e., dual ICD system). Among various charged CDs employed, it was found that beta-CD sulfate showed relatively wide enan tioselectivity for a wide variety of drugs under acidic conditions. Then se paration of enantiomers was performed by employing beta-CD sulfate and the effect of the addition of electrically neutral CDs to the buffers containin g beta-CD sulfate was investigated. Through the addition of electrically ne utral CDs to the buffers containing the charged CD, resolution of most of t he enantiomers was improved, compared with those with the charged CD alone. It was also found that the ring size (alpha, beta, gamma), the substitutio n groups and the concentration of the additional electrically neutral CDs a ffected the enantioselectivity. For example, alpha-CD addition was effectiv e for the separation of enantiomers of chlorpheniramine and hydroxypropyl-b eta-CD was effective for the enantiomer separation of trimetoquinol isomer. The application of the method in optical purity testing is also briefly me ntioned.