Dissipation, Residue Analysis, and Dietary Risk Assessment of Chlorantraniliprole and Indoxacarb in Rice

A residue analytical method for the determination of chlorantraniliprole and indoxacarb in brown rice, rice husk, and rice straw was validated using a revised QuEChERS method coupled with high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), and field trials were conducted in 12 regions to study the dissipation and final residues of the two pesticides in rice crop. In the method validation, chlorantraniliprole and indoxacarb had average recoveries ranging from 79% to 110%, with relative standard deviations (RSD) of 1.2% to 12.2%. The dissipation experiments showed that the half-lives of chlorantraniliprole in brown rice and rice husk were 12.4-29.8 and 4.6-11.2 d, respectively, whereas the dissipation half-lives of indoxacarb were 10.3-20.4 and 4.4-8.1 d, respectively. As for the final residues in the 12 regions, rice samples were collected on the 28 and 35 d after the last application. The maximum residues of chlorantraniliprole and indoxacarb in rice grain were 0.38 mg/kg and 0.080 mg/kg, respectively, and in brown rice, the maximum residues of chlorantraniliprole and indoxacarb were 0.028 mg/kg and 0.040 mg/kg, respectively. These values were all below the relevant Maximum Residue Limits (MRLs) in China. Using the final residue results and the food consumption data, the long-term dietary risk assessment indicated that the residues of these two pesticides in rice would not pose unacceptable dietary risk to the general population.