螺虫乙酯及其代谢物在梨和土壤中的残留及消解动态

为建立梨和土壤中螺虫乙酯及其代谢物螺虫乙酯-烯醇-糖苷 (S-glu)、螺虫乙酯-酮-羟基 (S-keto)、螺虫乙酯-烯醇 (S-enol) 和螺虫乙酯-单羟基 (S-mono) 的残留分析方法，以及明确螺虫乙酯在梨中的残留规律，采用体积分数为1%的乙酸乙腈为提取剂，以N-丙基乙二胺 (PSA) 和无水硫酸镁为分散净化剂的QuEChERS方法，利用超高效液相色谱-串联质谱 (UPLC-MS/MS) 在选择反应监测模式 (SRM) 下检测，外标法定量。结果显示:螺虫乙酯在0.0005~0.1 mg/L范围内，S-glu在0.005~0.5 mg/L范围内，S-keto、S-enol和S-mono在0.0005~0.5 mg/L范围内各化合物的质量浓度与质谱峰面积间均具有良好的线性关系 (R2 ≥ 0.999)；在0.005~0.7 mg/kg添加水平下，螺虫乙酯及其代谢物在梨果中的平均回收率为84%~109%，相对标准偏差 (RSD) 为1.2%~3.3%；在土壤中平均回收率为86%~102%，RSD为1.1%~3.6%。最低检测浓度 (LOQ)为5 μg/kg。该方法检测速度快、灵敏度高、重现性好，适用于梨和土壤中螺虫乙酯及其代谢物残留的快速检测和确证。按推荐剂量进行田间施药，当梨果成熟采收时，螺虫乙酯及其代谢物在梨中的残留量之和在0.023~0.056 mg/kg之间，低于中国规定的最大残留限量标准 (0.7 mg/kg)；在土壤中的残留量在0~0.015 mg/kg之间。螺虫乙酯及其代谢物在梨果和土壤中的消解动态均符合一级反应动力学方程，半衰期分别为为12.4 d和7.1 d。田间残留试验结果表明，螺虫乙酯用于梨树害虫防治是安全的。

Residues and dissipation dynamics of spirotetramat and its metabolites in pear and soil

A method for the simultaneous determination of spirotetramat and its metabolites such as spirotetramat-enol-glucoside(S-glu), spirotetramat-keto-hydroxy(S-keto), spirotetramat-enol (S-enol) and spirotetramat-mono-hydroxy(S-mono) in pear and soil was developed. The residual dissipation dynamics of spirotetramat in pears was determined. The residues in samples were extracted with acetonitrile(containing 1% acetic acid) and cleaned up by dispersivemethod with N-propylethylenediamine (PSA) and anhydrous magnesium sulfate as cleaning agents. Then the samples were detected by ultra performance liquid chromatography-tandem massspectrometry under selective reaction monitoring mode, and quantified by external standard method. The results showed good linearity (R2 ≥ 0.999) between mass concentration and peak area of mass spectra of each compound when the concentrations of spirotetramat ranged from 0.005 to 0.10 mg/L; S-glu from 0.005 to 0.5 mg/L; S-keto, S-enol and S-mono from 0.000 5 to 0.5 mg/L, respectively. When the fortified levels ranged from 0.005 to 0.7 mg/kg, the average fortified recoveries in pear were in the range of 84% to 109% and the reletive standard deviations (RSD) were 1.2%-3.3%. The average fortified recoveries in soil were in the range of 86% to 102% and the RSD were 1.1%-3.6%. The limits of quantification(LOQ) were 5 μg/kg. The method is rapid, sensitive and reproducible. Therefore, It is suitable for the rapid detection and identification of spirotetramat and its metabolite residues in pear and soil. According to the recommended dosage, the total residues of spirotetramat and its metabolites were 0.023-0.056 mg/kg in the fruit and 0-0.015 mg/kg in the soil when the pear was ripe and harvested. The half-life of spirotetramat in pear fruit was 12.4 d, and the half-life in soil was 7.1 d. Therefore, it is safe to use spirotetramat for the pest control of pear tree.