Selective extraction of sulfonamides, macrolides and other pharmaceuticals from sewage sludge by pressurized liquid extraction

A method for the quantitative determination of three macrolides, five sulfonamides, ranitidine, omeprazole and trimethoprim in sewage sludge samples was developed by using pressurized liquid extraction and high-performance liquid chromatography—electrospray ionization mass spectrometry. The extraction solvent and such operational parameters as temperature, pressure, extraction time and purge time were optimized in pressurized liquid extraction. The experimental conditions were: an extraction solvent of water (pH 3):methanol (1:1, v/v), a temperature of 80 °C, a pressure of 1500 psi, a sample weight of 5 g, an extraction time of 5 min, one cycle, a flush volume of 60% and a purge time of 120 s. All recoveries were over 74%, except those for ranitidine whose value was 54%. The repeatability and reproducibility between days expressed as relative standard deviation (n = 3) were lower than 11% and 15%, respectively. The limit of detection values ranged from 2 to 11 μg/kg dry weight (d.w.). The method was applied to determine the pharmaceuticals in sewage sludge from two domestic sewage treatment plants. Roxithromycin and tylosin were determined in the samples and tylosin showed the highest value (4.0 mg/kg d.w.).