Influence of Matrix When Tracing Cytostatic Drugs in Urban Wastewater: A Validated SPE-LC-MS/MS-Based Method

Cytostatic pharmaceuticals are not completely removed in wastewater treatment plants (WWTPs) and may affect aquatic ecosystems. Their quantification is challenging due to variations in wastewater characteristics, which influence analytical performance. An analytical procedure has been developed, based on solid-phase extraction and liquid chromatography coupled with tandem mass spectrometry, for the simultaneous quantification of 15 anticancer compounds. Influent and effluent samples from 14 Spanish WWTPs were analyzed, and 11 out of 15 target compounds were found at quantifiable levels (ng/L). These findings underscore the need for new WWTP treatments and the further development of analytical techniques capable of monitoring trace contaminants, in line with new regulatory demands. To carry out a comprehensive study of matrix influence on the analytical process, a novel physicochemical clustering approach was applied to group WWTPs, facilitating the validation of the method and widening its application to assess the load of micropollutants emitted to natural aquatic environments. Results show the influence of matrix variability on determining the concentration of cytostatics at both the influent and effluent of WWTPs. The interferences due to the matrix effect can be minimized by optimizing the dilution of the different samples.