Simultaneous determination of isoxaflutole and its two metabolites in corn under field conditions by LC-MS/MS

OBJECTIVE An improved QuEChERS method was established and verified for simultaneous determination of isoxaflutole and its metabolites diketonitrile and benzoic acid analogue residues in corn and plants. This method was mainly used to study the digestion rule and final residue level of isoxaflutole and its metabolites in corn and plants. It was hoped that the safe use of isoxaflutole in corn can be achieved eventually. METHOD The method was completed by means of ultra-performance liquid chromatography with triple quadrupole mass spectrometry. The extraction of the target substance was through acetonitrile solution containing 1% acetic acid, and the purification was through primary secondary amine, octadecylsilane and graphitized carbon black sorbent. RESULTS In the method, the quantitative limits and detection limits of the three analytes were 0.005-0.01 and 0.001-0.003 mg kg(-1) respectively. The half-life of isoxaflutole in the plants in Shandong and Anhui was 36.4 and 42.1 days respectively, and the digestion dynamics all conformed to the first-order kinetics. The final residues of isoxaflutole in green corn and mature corn were less than 0.02 mg kg(-1) of the maximum residue limit set by the Codex Alimentarius Commission. CONCLUSIONS The residual amount of isoxaflutole in corn and plants at harvest time was acceptable when isoxaflutole was applied once at a dose of 121.5 g a.i. ha(-1). (c) 2021 Society of Chemical Industry.