Combined use of carbon nanotubes and ionic liquid to improve the determination of antidepressants in urine samples by liquid chromatography

Antidepressants are widely used for the treatment of psychiatric disorders and therefore their monitoring in biological fluids is quite important taking into account that they can produce dangerous biochemical imbalances in toxic doses. A method for the determination of antidepressants in urine samples is presented using solid-phase extraction (SPE) and high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection. Home-made cartridges containing 30 mg multiwall carbon nanotubes are employed for isolation of the analytes from the sample, allowing also the preconcentration of the analytes prior to the HPLC analysis. Chromatographic separation was achieved in a reversed-phase C8 column using the ionic liquid 1-butyl-3-methylimidazolium trifluoromethanesulfonate as silanol activity suppressor, which enhances peak symmetry and chromatographic resolution. Limits of detection were 12.3 ng mL−1 for trazodone and 90.1 ng mL−1 for fluoxetine. The repeatability of the proposed method expressed as RSD (n = 11) varied between 3.4% (fluoxetine) and 5.0% (desipramine and mianserine). Thus, the method is suitable for the therapeutic monitoring of antidepressants in urine samples.