Application of QuEChERS extraction and LC-MS/MS for determination of pharmaceuticals in sewage sludges sampled across the Czech Republic.

The use of pharmaceuticals entails a significant risk of environmental contamination. Wastewater treatment plants (WWTPs) are considered to be the main contributors to contamination as they ineffectively eliminate these compounds from wastewater. Simultaneously, they produce solid waste, sludge, which often contains a variety of retained pollutants, including pharmaceuticals. Since sewage sludge is frequently applied to agricultural soil due to its rich nutrient content, pollutants are introduced into the environment in this way. Only a few studies have been carried out on the topic of the analysis of pharmaceuticals in sludge. Therefore, information on the occurrence of pharmaceuticals in sludge is limited. The present study employed quick, easy, cheap, effective, rugged and safe (QuEChERS) extraction and liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) analysis to establish a simple and reliable procedure for determining 16 pharmaceuticals (antibiotics, anticonvulsants, antidepressants and β-blockers) in sewage sludge. The method has been thoroughly validated, and parameters such as linear range, accuracy, precision, matrix effects and detection and quantification limits were assessed. Our method achieved low limits of quantification (0.5-9.0 µg kg^-1) and satisfactory recoveries (51-101%). Forty sludge samples from different WWTPs across the Czech Republic were analysed. Fourteen compounds were detected and quantified in most samples, with antidepressants having the highest detection frequency and overall content. Sertraline, with a mean concentration of 521.0 µg kg^-1, was notably prevalent alongside its metabolite norsertraline (mean concentration 204.9 µg kg^-1). The antibiotic azithromycin was also found at higher levels (mean concentration 185.1 µg kg^-1).