精甲霜灵与百菌清在黄瓜和土壤中的残留降解规律研究

Residue and Degradation of Mefenoxam and Chlorothalonil in Cucumber and Soil

[目的]研究精甲霜灵与百菌清在黄瓜和土壤中的残留状况与残留降解规律,评价精甲霜灵与百菌清在黄瓜上使用的安全性,建立同时测定黄瓜和土壤中精甲霜灵与百菌清残留量的液相色谱分析方法。[方法]黄瓜和土壤中的精甲霜灵与百菌清采用乙腈溶液振荡提取,使用酸性氧化铝固相萃取小柱净化,液相色谱带二极管阵列检测器(DAD)测定,外标法定量;田间试验按照NY/T 788-2004《农药残留试验准则》进行。[结果]在添加量为0.02～2.00 mg/kg时,精甲霜灵在黄瓜和土壤中的添加平均回收率为84.7%～101.0%,变异系数为2.72%～6.46%;当添加量为0.01～1.00 mg/kg时,百菌清在黄瓜和土壤中的添加平均回收率为76.9%～95.8%,变异系数为3.36%～4.90%。精甲霜灵的最小检出量为5×10-10 g,百菌清为2×10-10 g;精甲霜灵的最低检出质量分数为0.02 mg/kg,百菌清为0.01 mg/kg。精甲霜灵和百菌清在黄瓜和土壤中的残留消解动态符合方程Ct=Coe-kt;精甲霜灵在黄瓜中的半衰期为2.8～3.2 d,在土壤中的半衰期为7.8～9.8 d;百菌清在黄瓜中的半衰期为1.3～2.1 d,在土壤中的半衰期为3.7～4.0 d。在黄瓜上施用精甲霜灵.百菌清440 g/L悬浮剂,施药剂量为推荐用量990 g a.i/hm2和推荐用量的1.5倍1 485 g a.i./hm2,施药3～4次,末次施药1 d后黄瓜中的精甲霜灵残留量低于联合国食品法典委员会(CAC)规定的最大残留限量值(MRL)0.5 mg/kg,百菌清残留量低于CAC规定的MRL值5.0mg/kg。[结论]精甲霜灵.百菌清440 g/L悬浮剂按推荐剂量施用,1 d后收获的黄瓜食用安全。

[Objective] Dissipation dynamics and final residues for mefenoxam and chlorothalonil in cucumber and soil in field were investigated to provide an evaluation for the scientific,safe use of mefenoxam and chlorothalonil in cucumber,and a high-performance liquid chromatography（HPLC） method was established to determine residue for mefenoxam and chlorothalonil in cucumber and soil.[Method] Pesticide residue was extracted by acetonitrile,then purified by SPE with acid alumina,and determined by HPLC equipped with a DAD detector.[Result] At three spiking levels from 0.02-2.00 mg/kg,the average recoveries of the mefenoxam standards were within a range of 84.7%-101.0% with their relative standard deviations of 2.72%-6.46% in soil and cucumber;when the additive amount was 0.01-1.00 mg/kg,the average recoveries of the chlorothalonil standards were within a range of 76.9%-95.8% with their relative standard deviations of 3.36%-4.90% in soil and cucumber,respectively.Limit of detection was 5×10-10 g for mefenoxam,2×10-10 g for chlorothalonil and the lowest concentrations detected were 0.02 mg/kg for mefenoxam and 0.01 mg/kg for chlorothalonil in cucumber and soil,respectively.The result indicated that the degradation of mefenoxam and chlorothalonil in cucumber and soil could be described with equation：Ct=Coe-kt.The half life of mefenoxam was 2.8-3.2 d in cucumber and 7.8-9.8 d in soil,respectively.The half life of chlorothalonil was 1.3-2.1 d in cucumber and 3.7-4.0 d in soil,respectively.Mefenoxam·chlorothalonil 440 g/L suspension concentration applied at 3-4 times in cucumber with commanded dosage of 990 g a.i./hm2 and 1.5 times commanded dosage of 1485 g a.i./hm2.The residues of mefenoxam in cucumber was less than 0.5 mg/kg of maximum residue limit（MRL） of Codex Alimentarius Commission（CAC） and chlorothalonil less than 5.0 mg/kg of maximum residue limit（MRL） of CAC after 1 day.[Conclusion] Mefenoxam · chlorothalonil 440 g/L SC is acceptable to apply for cucumber under the recommended dosage.