In the environment, plants and animals in vivo, pesticides can be degraded or metabolized to form transformation products (TPs) or metabolites, which are even more toxic than parent pesticides. Hence, it was necessary to evaluate residue and risk of pesticides and their TPs (or metabolites). Here, a rapid, simple, and reliable method using QuEChERS and LC-MS/MS had been developed for simultaneous analysis of prothioconazole and its toxic metabolite, prothioconazole-desthio, in soil, wheat plant, straw, and grain. The average recoveries of prothioconazole and prothioconazole-desthio in four matrices ranged from 86 to 108% with relative standard deviations (RSDs) of 0.53-11.87% at three spiking levels. The method was successfully applied to investigate the dissipation and terminal residues of the two compounds in wheat field. It was shown that prothioconazole was rapidly degraded to prothioconazole-desthio, with half-lives below 5.82 days. Prothioconazole-desthio was slowly dissipated in soil and plant. The terminal residues of prothioconazole in wheat grain with a pre-harvest interval (PHI) of 21 or 28 days were below the maximum residue limits (MRLs) (0.1 mg/kg, Codex Alimentarius Commission (CAC)). We also evaluated the intake risk of prothioconazole-desthio residues in wheat grain in China. For long-term intake assessment, the hazard quotients (HQ) ranged from 1.30 to 5.95%. For short-term intake assessment, the acute hazard indexes (aHI) ranged from 1.94 to 18.2%. It indicated that the intake risk of prothioconazole-desthio in wheat consumption was acceptable. Thus, the prothioconazole application on wheat with the scientific practices would not pose public health risk.

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