Quantitation of oxcarbazepine and its metabolites in human plasma by micellar electrokinetic chromatography

Abstract

A reliable micellar electrokinetic chromatographic method for the determination of oxcarbazepine and its two main metabolites, 10‐hydroxycarbamazepine and 10,11‐trans‐dihydroxy‐10,11‐dihydroxycarbamazepine, in human plasma was developed. The separation and determination of the analytes was achieved using a system consisting of 60 mM SDS in phosphate buffer (30 mM, pH 8.0), to which 20% (v/v) methanol was added. Separation was carried out in an uncoated fused‐silica capillary with a separation voltage of 25 kV and currents typically less than 40 µA. Spectrophotometric detection was at 205 nm. Isolation of oxcarbazepine and its metabolites from plasma was accomplished by a solid‐phase extraction procedure. The mean extraction yield of the analytes from plasma was higher than 94%. The linear correlation coefficients were better than 0.994 for all analytes. The limit of detection was 0.05 µg/mL, the limit of quantitation 0.15 µg/mL. The repeatability for the spiked blank plasma samples was lower than 1.9% and the intermediate precision lower than 2.1%, both expressed as RSD%. The results obtained analysing real plasma samples from epileptic patients under therapy with Tolep® were satisfactory in terms of precision, accuracy and detectability. Copyright­© 2003 John Wiley & Sons, Ltd.