Determination of pyroxasulfone and its metabolites residues in three grains by UPLC-MS/MS

Based on the ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) technique, a residue analysis method was established for simultaneous determination of pyroxasulfone and its four metabolites (M1, M3, M25, M28) in maize, soybean and wheat. The samples were extracted by acetonitrile with 2%(V/V) formic acid, purified with 50 mg C₁₈, 50 mg graphitized carbon black (GCB), and 100 mg magnesium sulfate anhydrous, separated on a BEH-C₁₈ column, detected by UPLC-MS/MS in multiple reaction monitoring mode, and quantified with a matrix-matched external standard method. The results showed that the linear relation between the areas and the mass concentrations of all compounds was satisfied, given the correlation coefficient (r) above 0.99 within the concentration of 0.0005-0.02 mg/L. The average inter-day and intra-day recoveries of all compounds were 76%-96% with the relative standard deviations (RSD) of 8.8%-9.9% at the spiked levels of 0.01 to 0.1 mg/kg. The limits of quantification (LOQ) of the method were 0.01 mg/kg. The method validation parameters met the requirements of residue analysis, showing that it could be used for the detection of pyroxasulfone and its metabolites in the three crops.