Simultaneous determination of pyroxasulfone and its metabolites in wheat: Implications for safe application

Understanding pyroxasulfone residue dynamics in wheat under China's climatic and soil conditions is critical for establishing rational usage guidelines, setting maximum residue limits, and safeguarding human health. Field trials were conducted across 10 major wheat-producing regions to evaluate the residues of 40 % pyroxasulfone suspensions in winter wheat. A UPLC-MS/MS method was developed to simultaneously quantify pyroxasulfone and four metabolites in grains and straw. The method demonstrated recoveries of 73 %-93 %, with relative standard deviations (RSDs) of 7 %-15 % and a limit of quantification (LOQ) of 0.02 mg/kg. Only the M1 metabolite of pyroxasulfone was detected in straw (0.034-0.18 mg/kg), while residues of all five analytes in grains remained below the LOQ (<0.02 mg/kg). Dietary intake risk assessment confirmed low health concerns. To effectively control annual weeds in wheat fields, a single preemergence soil application of 40 % pyroxasulfone suspension at 180 g a.i./ha is recommended.