Separation of olanzapine, carbamazepine and their main metabolites by capillary electrophoresis with pseudo-stationary phases

Conditions were worked out for the separation of carbamazepine, olanzapine, and their main metabolites carbamazepine 10,11-epoxide, 10-hydroxycarbamazepine, and desmethylolanzapine. The separation was based on electrokinetically driven methods in the capillary format. The main difficulty in separating these compounds is related to their different chemical classes. Whereas the carbamazepine members are amides, and are electrically neutral, the olanzapine members have aliphatic amino groups and are thus cationic under most experimental conditions. Different additives were applied as pseudo-stationary phases to implement selectivity. Poly(diallyldimethylammonium), PDADMA, is a polycationic replaceable and soluble polymer, that interacts mainly according to the polarisability of the analyte molecules. The MEKC principle was applied with the common SDS as micelle former. In both systems, only partial resolution of the analytes was obtained. The most favorable system consisted of a charged, oligomeric additive: full separation of all analytes within 4 min was achieved with heptakis-6-sulfato-β-cyclodextrin (7 mM) in 30 mM borate buffer, pH 8.5.