Accurate Detection and Quantification of Nineteen Micropollutants by Online SPE-LC–MS/MS Method in Raw and Biologically Treated Wastewater: Assessment of Mobile Phase Composition and Matrix Effect

Abstract This study focused on developing an analytical method to quantify nineteen selected micropollutants (MPs), including pharmaceuticals and personal care products, in complex wastewater matrices. An online solid-phase extraction system coupled with LC–MS/MS was used, and different mobile phase compositions were tested in the chromatographic method. The validated method was subsequently applied to real influent and effluent samples from an anaerobic biological reactor in order to assess MP occurrence and removal behavior. The best results were achieved using a mixture of acetonitrile and methanol (50:50 v:v) with 0.1% formic acid, offering high resolution, ionization efficiency, and sensitivity. The method demonstrated good linearity, low detection limits (sewage: 12–143 ng L −1 ; effluent: 7–45 ng L −1 ), and RSD < 15%. Matrix effects were observed in both influent and effluent samples, leading to signal suppression. Despite this, the method maintained high selectivity and precision. Sewage presented variable MPs’ concentrations, with paracetamol being the most prevalent (12–20 µg L −1 ). Removal efficiencies varied among compounds: paracetamol, parabens, and trimethoprim exhibited high biodegradability (> 80%), whereas diclofenac and carbamazepine were poorly removed (< 20%). Application to real wastewater samples revealed highly variable influent concentrations and compound-dependent removal efficiencies, highlighting both the analytical challenges posed by complex matrices and the relevance of the method for evaluating biological treatment performance.