Identification and Dissipation of Omethoate and Its Main Metabolite DMP in Wheat Determined by UPLC-QTOF/MS

A study was carried out to evaluate the dissipation kinetics of field-applied omethoate during wheat storage. Both the identification and metabolic dynamics of omethoate metabolites were analyzed using UPLC-QTOF/MS. The presence of the metabolite dimethyl phosphate (DMP) was confirmed in wheat samples with applied omethoate. This might be because the group attached to the P atom of omethoate is replaced by a hydroxyl group through hydrolysis, thus leading to the formation of the specific metabolite DMP during wheat storage. Although the initial concentrations of DMP in different doses were considerably lower than those of omethoate, the half-life values of DMP were 11.87–31.50 days, which were close to the half-life of the parent omethoate (11.85–30.94 days). This indicates that potential health risks might be caused by dietary exposure to DMP and omethoate. Therefore, more importance should be given to the risk assessment for omethoate and its metabolite DMP in wheat.