Separation of five recently commercialized selective serotonin reuptake inhibitor antidepressants by capillary electrophoresis

Several strategies were applied in order to find a simple electrophoretic method for the investigation of five selective serotonin reuptake inhibitors (SSRI) (citalopram, fluoxetine, fluvoxamine, paroxetine, and sertraline). Variation of the pH and of the ionic strength of the background electrolyte (BGE) were studied, but did not enable separation of the analytes. A micellar electrokinetic chromatography (MEKC) strategy for the simultaneous separation of the five SSRIs was developed involving a sodium dodecylsulfate (SDS) MEKC system. The electroosmotic flow (EOF) and the migration of the analytes were determined for separation buffers of several surfactant concentrations and organic modifier percentages. The most favourable MEKC system consisted of 20 mmol/L SDS in a phosphate buffer (pH 7.5) with 30% methanol; the separation was carried out using an uncoated fused-silica capillary, a separation voltage of 25 kV with currents typically less than 40 ?A, and spectrophotometric detection at 200 nm. Full separation of the mixture with baseline resolution of all analytes was obtained.