The Stability Of Spirotetramat And Its Metabolites And Its Degradation On Cucumber And Soil

Spirotetramat is a new broad spectrum,high efficiency of tetronic acid derivatices with insecticidal and acaricidal,and has been wideky used in China.Spirotetramat could generate certain toxic metabolites in crops and soil environment after the application.Therefore,residual regularity of main metabolites of Spirotetramat and its residual persistence should take into consideration when researching the residue and degradation of Spirotetramat in crops and environment,and its very essential to evaluate the safety of spirotetramat.The mian research contents and conclusions are as follows:A multi-residue analysis method using LC/MS/MS has been established for determination of Spirotetramat and its metabolites in cucumber and soil samples.The average recovery of Spirotetramat and its metabolites in cucumber and soil samples ranged from 73.0%to 107.1%with the relative standard deviation(RSD)ranged from 0.5%to7.19%,and the limit of detection was 0.02 mg/kg when the spkied concentration was 0.02-2mg/kg.The stability of Spirotetrament and its metabolites in matrix standard solution was considered.Based on the results of static experiments,this paper gives some scientific suggestions on the storage time and mode of the collected samples,matrix standard solution and pretreated samples.Cucumber and soil samples after collected was recommended to freeze storage(-18?),and should not exceed 30 d.Both pretreated samples and spirotetramat and its metabolites matrix standard solution should be determined as soon as possible.It is recommended that the pretreated cucumber samples and cucumber matrix standard solution of Spirotetrament and its metabolites to be stored under the freezing condition(-18?)and LC/MS/MS determination should be conducted within 15 d,pretreated soil samples and soil matrix standard solution of Spirotetrament and its metabolites to be stored under the freezing condition(-18?)and LC/MS/MS determination should be conducted within 10 d.Metabolic behavior,degradation dynamics and residual regularity of Spirotetrament and its metabolites has been researched through two years field experiment in Hunan,Zhejiang and Guangdong province.The mian metabolites produced was Spirotetrament-enols and Spirotetrament-ketone hydroxyls after Spirotetrament applicated in cucumber and soil with a fater digestion.The half-lives of Spirotetrament in cucumber and soil were 0.93~1.93 d and0.83~1.32 d.The application of 25%Spirotetramat WDG in cucumber and soil according to the dosage and application recommended,Spirotetramat and its metabolites in the last application for more than 5 days after harvest in cucumber was less than 0.1mg/kg in three different ecological conditions,less than the maximum residue limit(MRL)of cucumber in China(0.2 mg/kg).Therefore,it is suggested that the reasonable usage of 25%Spirotetramat WDG on cucumber is 180 g/hm~2(effective component of Spirotetramat is 45 g/hm~2)at most twice,and the safe interval is about 5 days.