A new sample preparation method for determination of acidic drugs in sewage sludge applying microwave assisted solvent extraction followed by gas chromatography–mass spectrometry

This paper presents a new sample preparation procedure for determination of selected acidic pharmaceuticals (ibuprofen, naproxen, ketoprofen, and diclofenac) in sewage sludge using microwave assisted solvent extraction, dispersive matrix extraction (DME) followed by the conventionally applied solid phase extraction (SPE), derivatization, and gas chromatography–mass spectrometry. The recoveries calculated from analytical data of spiked sludge samples changed in the range of 80–105% ± 15% for the four pharmaceuticals in mixed and activated sludge depending on the efficiency of the clean-up procedure. The measured concentration values of ibuprofen and naproxen were identical in the mixed and the activated sludge samples. However, ketoprofen and diclofenac showed about twice as high concentration in activated sludge than in the mixed one independently of the applied extraction method. The typical concentration ranges of ibuprofen, naproxen, ketoprofen and diclofenac in sewage sludge were 10–30 ng/g, 30–50 ng/g, 50–130 ng/g, and 50–140 ng/g respectively.