Development of a SPE-HPLC–MS/MS method for the determination of most prescribed pharmaceuticals and related metabolites in urban sewage samples

• Development of a multi-target method to quantify 55 targets in sewage samples.
• Selection of pharmaceuticals based on regional prescription data.
• SPE of small-volume samples with high accuracy and reproducibility.
• Time and cost saving due to small-volume samples and short analysis time.

Based on regional prescription data several pharmaceuticals with variable amounts of prescription and corresponding metabolites were selected and analyzed in influent and effluent samples of the sewage treatment plant (STP) in Dresden, Germany. Pharmaceuticals of the following most prescribed therapeutic groups were chosen: antibiotics, antifungals, anticonvulsants, antipsychotics, antidepressants, and cardiovascular active compounds like beta blockers and angiotensin-converting enzyme inhibitors. To analyze the selected compounds, a multi-target method was developed and applied to 24-h composite wastewater samples for three single days in May and June 2014. The method was based on a cleanup of a sample with a volume of 1 mL using solid phase extraction followed by a high performance liquid chromatography coupled to a tandem mass spectrometer. Analytes were separated in a 15 min chromatographic separation and quantified using 23 Internal Standards and a calibration curve in 40-fold diluted blank urine. The limit of quantification varied between 50 and 200 ng/L and for all analytes good accuracy and precision as well as linearity for the calibration curve with the correlation coefficient R2 higher than 0.99 was reached. A total of 41 and 40 of the selected 55 analytes were detected and quantified in the influent and effluent samples of the studied STP, respectively. Valsartan was the compound with the highest maximum concentration in influent (27.1 μg/L) and effluent (15.7 μg/L). Furthermore, analytes like bezafibrate, candesartan, carbamazepine, gabapentin, metoprolol, levetiracetam, pregabalin and telmisartan as well as the metabolite O-desmethyl venlafaxine were detectable in influent and effluent samples, respectively, with a concentration higher than 1 μg/L.