Residual behavior of chlorantraniliprole and lambda-cyhalothrin in cowpea and soil

The residue and dissipation dynamic of chlorantraniliprole and lambda-cyhalothrin in cowpea and soil were investigated. A dispersive solid phase extraction method was established for the pretreatment, while LC-MS/MS and GC-ECD chromatography were employed for the analysis. The result has shown that the recovery rate ranges from 80% to 105% and the variation coefficient ranges from 0.70% to 9.5%, when chlorantraniliprole and lambda-cyhalothrin are added to the cowpea and soil at the concentration ranging from 0.005 to 1 mg/kg (four concentrations). The half-lives of chlorantraniliprole and lambda-cyhalothrin in cowpea at Beijing and Hainan are 4-6 days; The half-lives of chlorantraniliprole and lambda-cyhalothrin in soil in the above mentioned two regions are 10-24 days. The residues in stems of cowpea were lower than 0.2 mg/kg at the harvest time. We recommend Good Agricultural Practices of chlorantraniliprole and lambda-cyhalothrin 14% aqueous capsule suspension (CS) used in cowpea are as follows:maximum using dose is 45 g a. i/hm2, spray at growth phase and no more than 3 times, applying pesticide interval is 7 days, and preharveat interval is 5 days.