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A rapid and sensitive method was developed for the simultaneous determination of fluoxetine and its primary metabolite, norfluoxetine, in plasma. It was based on a column-switching approach with a precolumn packed with large size particles coupled with a liquid chromatography-electrospray ionisation-mass spectrometry (LC-ESI-MS). After a simple centrifugation, plasma samples were directly injected onto the precolumn. The endogenous material was excluded thanks to a high flow rate while analytes were retained by hydrophobic interactions. Afterwards, the target compounds were eluted in back flush mode to an octadecyl analytical column and detected by ESI-MS. The overall analysis time per sample, from plasma sample preparation to data acquisition, was achieved in less than 4 min. Method performances were evaluated. The method showed good linearity in the range of 25-1000 ng mL(-1) with a determination coefficient higher than 0.99. Limits of quantification were estimated at 25 ng mL(-1) for fluoxetine and norfluoxetine. Moreover, method precision was better than 6% in the studied concentration range. These results demonstrated that the method could be used to quantify target compounds. Finally, the developed assay proved to be suitable for the simultaneous analysis of fluoxetine and its metabolite in real plasma samples.

The potential of nonaqueous capillary electrophoresis was investigated for the simultaneous separation of fluoxetine hydrochloride, its meta-isomer, and other related compounds. The resolution of these compounds was compared in aqueous and nonaqueous media. Baseline separation of the studied solutes required a buffer electrolyte solution composed of 25 mM ammonium acetate and 1 M acetic acid in acetonitrile, an applied voltage of 30 kV and a temperature of 20 degrees C. Selectivity was considerably affected by the nature of the solvent (water, methanol, and acetonitrile). Moreover, substituting acetate by formate in the background electrolyte resulted in migration time changes, which were attributed to an ion-pairing phenomenon. Finally, the method was successfully coupled on-line with electrospray ionization-mass spectrometry (ESI-MS) and allowed significant selectivity and sensitivity enhancement. The effect of ESI-MS parameters, such as nebulizing gas pressure, sheath liquid composition and flow rate, on resolution and method sensitivity was also discussed.