高效液相色谱－荧光法测定甲氨基阿维菌素苯甲酸盐在烟叶及土壤中的残留及消解动态

目的]建立柱前衍生高效液相色谱-荧光法测定烟叶和土壤中甲氨基阿维菌素苯甲酸盐残留量的方法。方法]样品经乙腈提取,分散固相萃取净化,以N-甲基咪唑和三氟乙酸酐进行柱前衍生,衍生物用高效液相色谱-荧光法测定。结果]当添加浓度为0.000 5~1.000 0 mg/kg时,甲氨基阿维菌素苯甲酸盐的平均添加回收率均超过90%,相对标准偏差(RSD)为2.3%~5.5%。在鲜烟叶、干烟叶和土壤中,方法最低检出浓度(LOQ)分别为0.004、0.008和0.000 5 mg/kg。采用所建方法测定了2014~2015年山东、四川烟叶和土壤样品中甲氨基阿维菌素苯甲酸盐的消解动态及最终残留,结果表明,甲氨基阿维菌素苯甲酸盐在烟叶和土壤中消解半衰期为4.4~5.4和1.6~2.6 d。按照2.25和3.375 g a.i./hm2用量,分别施药2~3次,采收间隔期7 d时,烤后烟叶样品中甲氨基阿维菌素苯甲酸盐残留量低于0.2 mg/kg。结论]该方法操作简便,有机溶剂用量少,符合农药残留检测技术对灵敏度、准确度及精密度的要求。

Dissipation and Residue of Emamectin Benzoate in Tobacco and Soil Using High Performance Liquid Chromatography Coupled to Fluo-rescence Detection

Objective] To establish a high performance liquid chromatography with fluorescence detection (HPLC-FLD) method for the determi-nation of emamectin benzoate residue in tobacco leaves and soil . Method] The sample was extracted by acetonitrile and then cleaned up by dis-persive solid phase extraction.After pre column derivatization with N-methyl imidazole and three trifluoroacetic anhydride ,the derivatives were determined by HPLC-FLD.Result] In the range of 0.000 5-1.000 mg/kg,the average recoveries of emamectin benzoate were higher than 90%,with the relative standard deviation (RSD) 2.3%-5.5%.The limits of quantification (LOQ) of emamectin benzoate in fresh tobacco leaves,cured tobacco leaves and soil were 0.004,0.008 and 0.000 5 mg/kg,respectively.The dissipation and residue levels of emamectin benzo-ate in Shandong and Sichuan in 2014-2015 were investigated using the established method .The field trials results showed that the half-lives of emamectin benzoate in tobacco leaves and soil were 4.4-5.4 day and 1.6-2.6 day,respectively.When applied at the dosage of 2.25 and 3.375 g a.i./hm2 for 2-3 times,the terminal residues of emamectin benzoate in cured tobacco leaves with a pre-harvest interval of 7 days were lower than 0.2 mg/kg.Conclusion] This method has the characteristics of simple operation,small dosage of organic solvent,which meets the re-quirements of sensitivity,accuracy and precision of pesticide residues detection technology .