A field experiment was conducted to study the residue and degradation dynamics and final residues of metalaxyl and cymoxanil in pepper and soil by liquid chromatography-tandem mass spectrometry.The degradation dynamic test results showed that the half-life of metalaxyl and cymoxanil in soil was 8.2~9.3 days and 1.8~2.1 days respectively and the half-life of metalaxyl and cymoxanil in pepper was 6.0~7.7 days and 1.9~2.0 days.The final residue test results showed that when 25% WG of metalaxyl and cymoxanil was applied with the dose of 625.0、937.5 mg a.i./kg, interval of 7 days and continuous root irrigation for 3 to 4 times, after root irrigating for 14~21 days, the final residues of metalaxyl in pepper and soil were 0.0380~0.3100 mg/kg and 0.1110~0.3580 mg/kg respectively, which were lower than the maximum residue limit (MRL) of 0.5 mg/kg;the cymoxanil in pepper and soil were not detected.Therefore, the application safety interval was suggested to be 14 days when 25% WG of metalaxyl and cymoxanil was applied at recommended dosage on pepper.%通过田间试验,对25%甲霜灵·霜脲氰水分散粒剂在辣椒和土壤中的残留消解动态及最终残留量进行了研究,采用高效液相色谱-串联质谱进行定量分析.消解动态试验结果表明:甲霜灵在土壤中的半衰期为8.2~9.3 d,霜脲氰在土壤中的半衰期为1.8~2.1 d;甲霜灵在辣椒中的半衰期为6.0~7.7 d,霜脲氰在辣椒中的半衰期为1.9~2.0 d.最终残留量试验结果表明:25%甲霜灵·霜脲氰水分散粒剂按施药剂量为625.0、937.5 mg a.i./kg,连续灌根3~4次,施药间隔期7 d,施药后14~21 d辣椒中甲霜灵残留量为0.0380~0.3100 mg/kg,土壤中甲霜灵残留量为0.1110~0.3580 mg/kg,均低于0.5 mg/kg(MRL);辣椒和土壤中霜脲氰均未检出.推荐25%甲霜灵·霜脲氰水分散粒剂在辣椒上的使用安全间隔期为14 d.
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