Residues And Degradation Of Diafenthiuron In Cabbage And Soils

Diafenthiuron is insecticide and acaricide which kills larvae, nymphs and adults by contact and/or stomach action; also shows some ovicidal action. Widely applies in the fruit tree, the grain cotton and kapok, the vegetables and decorative plant's plant disease prevention.Residue detection and degradation of diafenthiuron in cabbage and soil were investigated and its residue was determined with high-performance liquid chromatography. The samples of cabbage and soil were extracted with acetonitrile, further cleaned up by reverse solid phase dispersion, and analyzed by reversed-phase HPLC with diode array detector (DAD). Average recoveries of diafenthiuron was found in the range of 82.5%～100.9% at three spiking levels from 0.05 mg/kg to 5.0 mg/kg with relative standard deviations of 4.5%～7.5%,indicating that this method is fast accurate and responsible. A supervised trial experiment was conducted to study the residual dynamics and final residues of diafenthiuron in cabbage and soil, respectively. The results showed as follows:(1)The degradation of diafenthiuron in cabbage and soil could be described with equation :Ct=C0e-kt.(2) The half-life of diafenthiuron10%ME was 2.87-2.99 days in cabbage and 3.37-3.57 days in the soil. The results showed that diafenthiuron dissipated rapidly in cabbage and soil. The terminal residues of diafenthiuron in cabbage samples were very low. Cabbage was treated with diafenthiuron once and twice by interval of 7 days at the application dosage of 125g/666.7m2 and 250g/666.7m2 during the whole growing season of cabbage. The final residue of diafenthiuron in cabbage was found to be in a range of below 0.18mg/kg in Beijing and in other range of below 0.24mg/kg in Lengshuijiang, respectively. The final residues of diafenthiuron in the tested soils were found to be in a range of 0.09～0.37mg/kg in Beijing and in other range of 0.11～0.46mg/kg in Leng shuijiang, respectively, after the last application 7 and 14days.(3) The half-life of diafenthiuron25%EC was 2.91-3.02 days in cabbage and 3.36-3.54 days in the soil. Cabbage was treated with diafenthiuron once and twice by interval of 7 days at the application dosage of 50ml/666.7m2 and 100ml/666.7m2 during the whole growing season of cabbage. The final residue of diafenthiuron in cabbage was found to be in a range of below 0.15mg/kg in Beijing and in other range of below 0.20mg/kg in Lengshuijiang, respectively. The final residues of diafenthiuron in the tested soils were found to be in a range of 0.09～0.39mg/kg in Beijing and in other range of 0.11～0.43mg/kg in Leng shuijiang, respectively, after the last application 7 and 14days The use of diafenthiuron in cabbage could be considered to be safe. Ensure edible safety of cabbage.