Determination of topiramate in human plasma by capillary electrophoresis with indirect UV detection

A rapid capillary zone electrophoresis method with indirect UV detection for the determination of topiramate in human plasma was developed and validated. The analyses were carried out with a background electrolyte composed of 10mM sulfamethoxazole as chromophore in phosphate buffer (25 mM, pH 12.0); gabapentin was selected as the internal standard. Application of a voltage of +15 kV led to an analysis time shorter than 5 min; indirect UV detection was operated at 256 nm. Isolation of topiramate from plasma was accomplished by a carefully implemented solid-phase extraction procedure on C18 cartridges. The method provided a linear response over the concentration range of 2-60 microg of topiramate per mL of plasma. The limit of detection (LOD) was 0.8 microg mL(-1) and the limit of quantitation (LOQ) was 2.0 microg mL(-1). Precision, expressed as relative standard deviation, was always lower than 7.3%, extraction yields were always greater than 92%. The results obtained analysing plasma samples from epileptic patients undergoing therapy with topiramate were satisfactory in terms of precision and selectivity.