Determination of sertraline and N-desmethylsertraline in human plasma by means of capillary electrophoresis with laser-induced fluorescence detection

A method has been developed for the analysis of the antidepressant drug sertraline together with its main metabolite N-desmethylsertraline in human plasma. It is based on capillary electrophoresis with laser-induced fluorescence (LIF) detection (lambda = 488 nm). A solid phase extraction procedure is employed for biological sample pre-treatment, followed by a derivatisation step with fluorescein isothiocyanate; reboxetine was the internal standard. The effect of cyclodextrin, acetone and N-methyl-glucamine as constituents of the background electrolyte for analyte separation was investigated. The final background electrolyte consisted of 20 mM carbonate buffer, pH 9.0, with 2.5 mM heptakis(2,6-di-O-methyl)-beta-cyclodextrin, 50 mM N-methylglucamine and 20%, v/v acetone. With 30 kV applied voltage the electrophoretic run is completed in 7.5 min. Linearity was observed in the plasma concentration range from 3.0 to 500 ng/mL for sertraline and 4.0 to 500 ng/mL for desmethylsertraline. Extraction yield was >97.1%, precision - expressed as RSD% - was <3.7, accuracy (recovery) was >95.6%. Due to its sensitivity and selectivity the method was suited for the analysis of plasma samples from patients undergoing therapy with sertraline.