噻虫胺在番茄和土壤中的残留及消解动态

Residue and dissipation of clothianidin in tomatoes and soil

通过两年3地的田间试验,采用分散固相萃取-液相色谱-串联质谱法,研究了50%噻虫胺水分散粒剂在番茄和土壤中的残留及消解动态。结果表明:在0.005、0.01和0.05 mg/kg添加水平下,噻虫胺在番茄中的回收率为90%~121%,相对标准偏差(RSD)为4.0%~4.5%(n=5),在土壤中的回收率为88%~92%,RSD为3.6%~5.8%(n=5),番茄和土壤中噻虫胺的定量限均为0.005 mg/kg,可满足现有限量标准的要求。噻虫胺在番茄中的消解动态符合准一级动力学方程,半衰期为3.5~17.3 d。当50%噻虫胺水分散粒剂以推荐剂量(有效成分)60 g/hm2在番茄生长到成熟个体一半大小时施药3次,施药间隔7 d时,噻虫胺在番茄上的最终残留量在<LOQ^0.32 mg/kg之间,远低于日本规定的最大允许残留量(MRL)值3 mg/kg,推荐采收安全间隔期为1 d。

A two-year field experiment was conducted to study the residue and dissipation dynamics of clothianidin（50% WDG） in tomatoes and soil in three locations. The dispersive solid phase extraction（DSPE） combined with high performance liquid chromatography-tandem mass spectrometry（HPLCMS/MS） method was developed for the rapid determination of the clothianidin residue in tomatoes and soil. The results indicated that the recoveries at spiked level of 0.005, 0.01 and 0.05 mg/kg in tomatoes were in the range of 90%-121%, with relative standard deviation of 4.0%-4.5%（n=5）; and the recoveries for soil samples were in the range of 88%-92%, with relative standard deviation of 3.6%-5.8%（n=5）. The limits of quantitation（LOQ） for clothianidin in tomatoes and soil were both 0.005mg/kg, which could meet the requirement of max residue limits（MRLs） of clothianidin. The dissipation dynamics of clothianidin in tomatoes fitted the pseudo-first-order kinetics equations, and the half-lives of clothianidin were estimated to be 3.5-17.3 d in tomatoes. If tomatoes were treated three times and interval of 7 days with the available dosage of 60 g/hm^2 during the growing season, the final residue of clothianidin is LOQ-0.32 mg/kg. According to the MRL of Japan, the harvest interval was recommended to be 1 d.