Suspect and non-target screening of pesticides and pharmaceuticals transformation products in wastewater using QTOF-MS

Pesticides and pharmaceuticals are widely used in modern life and are discharged into wastewater after usage. However, a large number of transformation products (TPs) are formed through abiotic (hydrolysis/photolysis, etc.) and biotic (aerobic/anaerobic degradation by micro-organisms) wastewater treatment processes, and the structure and potential risk of TPs are still unclear. In this study, a suspect and non-target screening was performed to monitor these chemicals with HPLC-QTOF-MS. We identified 60 parent compounds by suspect screening in three Chinese wastewater treatment plants with the commercial database of pesticides and pharmaceuticals, and they were confirmed by authentic standards. Then, suspect and non-target screening strategies based on the predicted diagnostic fragment ions were used to screen TPs of the 60 parent compounds. We tentatively identified 50 TPs and confirmed thirteen of them with authentic standards. Among 13 quantified TPs, about 40% of them showed higher concentration than their parent compounds in effluent. Especially, cloquintocet, as a TP of cloquintocet-mexyl, had a concentration ratio TP/parent = 14,809 in effluent. Twenty-five TPs had higher predicted toxicity than the corresponding parent compounds by calculating their LC₅₀ values towards aquatic organisms using toxicity prediction software. Twenty identified TPs were firstly reported in this study. These results indicate the importance of TP analysis in environmental monitoring in wastewater.