Dissipation dynamics and dietary risk assessment of prodiamine in rice by modified QuEChERS method combined with HPLC-MS

Prodiamine is a dinitroaniline herbicide which can be tried for weed control in rice fields because of its unique mode of action. Its behavior in the rice paddy environment needs to be studied before trying to use. Its dissipation and residues in the paddy environment were studied using HPLC-MS coupled with the modified QuEChERS method to assess the safety of its use in rice plantations. The LOD and LOQ of prodiamine in rice field substrate extracts ranged from 0.0069 to 0.0185 mg/kg and 0.00201–0.00550 mg/kg, respectively. The method exhibited high linearity (R2 ≥ 0.99) within the concentration range of 0.01–5 mg/L. Intra-day and inter-day recoveries ranged from 84.11% to 115.27% with RSDr of 1.29∼7.67% and RSDR of 1.99–7.70%. Meanwhile, the dynamics of prodiamine dissipation in paddy soil and rice plants followed a first-order kinetic model, with the half-life (t0.5) ranging from 11.02 to 14.95 d and 4.81–5.55 d, respectively, indicating a high rate of dissipation. The final residue results showed that the residues in the rice plants of prodiamine at harvest were mainly concentrated on the rice husk. Further chronic dietary risk assessment revealed that the residues of prodiamine in brown rice did not pose any health risk to humans.