Rapid quantification method of pharmaceuticals in urban wastewater using UHPLC-Orbitrap mass spectrometry – a multi target approach for EU-directive advanced treatment evaluation

Abstract

Pharmaceutical residues have become contaminants of emerging concern in wastewater, as inadequate removal by wastewater treatment plants can result in ecotoxicological impacts on aquatic ecosystems. For this reason, the EU Urban Wastewater Treatment Directive (UWWTD 2024/3019) requires the implementation of quaternary treatment upgrades and the regular monitoring of their effectiveness in European Wastewater Treatment Plants (WWTPs). In this study, a sensitive, reliable, and cost-effective analytical method was developed and validated for the simultaneous determination of twelve indicator substances, including nine compounds proposed by the UWWTD, and three substitutes in various influent and effluent of WWTPs. The method is based on solid-phase extraction (SPE) of 2-mL-wastewater samples using, followed by reversed-phase liquid chromatography coupled to high-resolution mass spectrometry (LC-HRMS) employing an Orbitrap Exploris™ 240. Detection was carried out using heated electrospray ionization in positive ionization mode (HESI+), except diclofenac (HESI-). Quantification was performed using SIM scans, while high-resolution full-scan spectra were acquired for confirmation. Limits of Quantification (LOQ) ranged mostly between 15 and 30 ng/L, except for candesartan, irbesartan and diclofenac with LOQ > 50 ng/L. A laboratory validation demonstrated high precision and accuracy for all selected pharmaceuticals. Further, the method was successfully applied to raw and treated wastewater from WWTPs of different size classes in the border region of Saxony (Germany) and Northern Bohemia (Czech Republic). This method therefore offers a rapid quantification approach for assessing the removal efficiency of pharmaceuticals and potential substitutes categorized in the UWWTD.