Optimization of the SPME parameters and its online coupling with HPLC for the analysis of tricyclic antidepressants in plasma samples.

Solid-phase microextraction (SPME)-liquid chromatography (LC) is used to analyze tricyclic antidepressant drugs desipramine, imipramine, nortriptyline, amitriptyline, and clomipramine (internal standard) in plasma samples. Extraction conditions are optimized using a 2(3) factorial design plus a central point to evaluate the influence of the time, temperature, and matrix pH. A Polydimethylsiloxane-divinylbenzene (60-mum film thickness) fiber is selected after the assessment of different types of coating. The chromatographic separation is realized using a C(18) column (150 x 4.6 mm, 5-microm particles), ammonium acetate buffer (0.05 mol/L, pH 5.50)-acetonitrile (55:45 v/v) with 0.1% of triethylamine as mobile phase and UV-vis detection at 214 nm. Among the factorial design conditions evaluated, the best results are obtained at a pH 11.0, temperature of 30 degrees C, and extraction time of 45 min. The proposed method, using a lab-made SPME-LC interface, allowed the determination of tricyclic antidepressants in in plasma at therapeutic concentration levels.