Analysis of paroxetine, fluoxetine and norfluoxetine in fish tissues using pressurized liquid extraction, mixed mode solid phase extraction cleanup and liquid chromatography–tandem mass spectrometry

Recent studies have shown that selective serotonin reuptake inhibitors (SSRIs) such as fluoxetine are accumulated in the tissues of fish as a result of discharges of pharmaceuticals into surface waters from municipal wastewater treatment plants. In this study, an analytical method based on liquid chromatography with atmospheric pressure chemical ionization and tandem mass spectrometry (LC–APCI-MS/MS) was developed and validated for the determination of residues of paroxetine, fluoxetine and its active metabolite, norfluoxetine, in fish tissue. The procedure for sample preparation includes extraction of tissue by pressurized liquid extraction (PLE), followed by cleanup on a mixed-mode solid phase extraction (SPE) cartridge, Oasis® MCX. With the optimized method, matrix interferences were reduced and recoveries >85% were obtained. The limits of quantitation (LOQ) determined by analysis of spiked fish tissue were 0.24, 0.07, and 0.14 ng/g wet weight for paroxetine, fluoxetine and norfluoxetine, respectively. This method was successfully applied to the analysis of samples of fish collected from Hamilton Harbour in Ontario, Canada, which is an urbanized and industrialized embayment of Lake Ontario. These analyses showed that the three analytes were present in fish tissues at concentrations up to approximately 1 μg/kg wet weight.