气相色谱-质谱法测定乙螨唑在苹果和土壤中的残留及消解动态

采用气相色谱-质谱联用(GC-MS)法,测定了乙螨唑在苹果和土壤中的残留及消解动态。土壤样品经丙酮提取,苹果样品经V(丙酮)∶V(乙酸乙酯)=1∶1混合溶液提取,两者均无需净化,采用气相色谱-质谱联用(GC-MS)仪测定。结果表明:在0.01、0.1和1 mg/kg 3个添加水平下,乙螨唑在苹果中的平均回收率为93%~96%,相对标准偏差(RSD)为2.8%~8.0%;在土壤中的平均回收率为91%~104%,RSD为0.70%~8.3%;最小检出量为0.001 ng,最低检测浓度为0.01 mg/kg。国际食品法典委员会(CAC)、中国和美国均未制定乙螨唑在苹果上的最大残留限量值(MRL),日本规定乙螨唑在苹果上的MRL值为2.0 mg/kg。本研究参考日本规定,采用150 g/L乙螨唑悬浮剂按有效成分30 mg/L剂量(推荐剂量的1.5倍)施药,其在苹果和土壤中的半衰期分别为7.4~14.2 d和4.2~18.1 d,施药后21 d苹果中乙螨唑的最终残留量≤1.65 mg/kg。

Residues and decline study of etoxazole in apple and soil by gas chromatography-mass spectrometry method

A gas chromatography-mass spectrometry (GS-MS) method was developed for determining etoxazole residues in apple and soil. The soil samples were extracted with acetone and the apple samples were estracted with a mixture of proportionate acetone and ethyl acetate(1 :1,V/V). All the samples were tested by GC-MS without cleanup. Results showed that the ranges of average recoveries and relative standard deviations of the method were 93% to 96% in apple and 91% to 104% in soil, 2.8% to 8.0% in apple and 0.70% to 8.3% in soil respectively, at fortified levels of 0.01 to 1 mg/kg. The limit of detection was estimated to be 0.001 ng, and the limit of quantification was 0.01 mg/kg. International codex alimentarius commission (CAC), China and the United States do not stipulate the MRL of etoxazole in apple but the MRL is 2.0 mg/kg in Japan. Refer to the stipulation, sprayed with high dosage of 30 mg(a.i.)/L for etoxazole 150 g/L EW, the results of residue dynamics indicated that the half-lives of etoxazole in apple and soil were 7.4-14.2 d and 4.2-18.1 d, respectively. Terminal residues in apples were less 1.65 mg/kg after 21 days.