Comparison of two extraction methods for the determination of selective serotonin reuptake inhibitors in sewage sludge by hollow fiber liquid-phase microextraction

This paper presents two procedures for the determination of four selective serotonin reuptake inhibitors (citalopram, paroxetine, fluoxetine, and sertraline) and one metabolite (norfluoxetine) in sewage sludge utilizing three-phase hollow fiber liquid-phase microextraction (HF-LPME). First, direct HF-LPME was used for extraction, clean-up, and preconcentration. The pharmaceuticals were extracted from slurry samples into an organic phase and then back-extracted into an aqueous phase in the lumen of the hollow fiber. Second, a procedure combining pressurized hot water extraction and HF-LPME for clean-up and preconcentration was developed for the same analytes and matrix. The extracts were subsequently analyzed by liquid chromatography-mass spectrometry. For direct HF-LPME, limits of detection were between 1 and 12 ng g(-1) (dry weight) and the relative standard deviation (RSD) values were 3-12%. For the second method, limits of detection were approximately 6 ng g(-1) for all the compounds and RSD values were 8-12%. The methods were validated by comparison of results for the same samples. Sewage sludge from a Swedish wastewater treatment plant was analyzed by both methods; average concentrations were similar for citalopram, paroxetine, and fluoxetine with values of approximately 530, 40, and 200 ng g(-1) , respectively.