Untargeted screening, quantitative analysis, and toxicity estimation of degradation products of fluazinam in vegetables

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Fluazinam exhibits rapid degradation in some vegetable matrixes. The degradation products may pose risk for human health. In the present study, three degradation products of fluazinam in vegetables have been identified, named as sulfhydryl fluazinam, hydroxyl fluazinam, and amine fluazinam. Among them, sulfhydryl fluazinam has not been previously reported. Quantitative/semi-quantitative method for simultaneous analysis of fluazinam and the three degradation products was developed using QuEChERS in combination of HPLC-MS/MS. The proposed analytical method was further applied in monitoring fluazinam and its degradation products in fluazinam-processed vegetables. As a result, sulfhydryl fluazinam was demonstrated to be a characteristic degradation product of fluazinam in the sulphur-rich vegetables with transformation rates of above 10.0% within 60.0 min. In addition, we found for the first time that sulfhydrylation of pesticide occurred in putrid vegetable samples covering various plant families. The result contributed to discovery of the overlooked degradation pathways of pesticides in vegetables. Among fluazinam and the three degradation products, amine fluazinam was predicted to have highest toxicity, followed by sulfhydryl fluazinam and fluazinam, whereas hydroxyl fluazinam displayed the lowest toxicity. Cytotoxicity experiments in BRL-3A cells showed that toxicity of sulfhydryl fluazinam was comparable to that of fluazinam. In short-term oral studies in mice, liver appeared to be a target organ for sulfhydryl fluazinam. The present study not only provides an efficient analysis method, but also inspires further comprehensive risk assessment of fluazinam and its degradation products in vegetables.