Suspect screening of emerging organic micropollutants using high-resolution mass spectrometry: case of the Litani River in Lebanon.

This study describes a detailed workflow for the suspect screening of emerging organic micropollutants in surface water samples from the Litani River in Lebanon. Target classes include pharmaceuticals, illicit drugs and stimulants, hormones, pesticides, and some of their metabolites. The analytical approach involved an offline solid-phase extraction followed by liquid chromatography coupled to high-resolution quadrupole time-of-flight mass spectrometry (LC-QqTOF/HRMS). Spectral acquisition was achieved using full-scan TOF-MS followed by data-dependent acquisition (DDA) and Sequential Window Acquisition of All Theoretical Mass Spectra (SWATH). Utilizing a suspect list of approximately 850 compounds, the screening identified 75 organic micropollutants at level 2a confidence based on mass spectral library matching using DDA-generated spectra. Post-acquisition data processing with mass error filtering applied to DDA enabled the refinement of a priority list for targeted quantitative monitoring. The list includes 43 pharmaceuticals, 10 hormones, 8 illicit drugs and stimulants, and 14 pesticides. Among the identified compounds, 20 were further confirmed at level 1 confidence through direct comparison with reference standards. Prioritization of the compounds based on detection frequency revealed that the pharmaceuticals valsartan (96 %), climbazole (85 %), trimethoprim (78 %), the pesticide N,N-diethyl-meta-toluamide (81 %), and the illicit drug cocaine (78 %) are the most consistently detected organic micropollutants across samples. The findings from this study establish a wide scope baseline dataset for future quantitative monitoring and risk assessment.