Research On The Residual Digestion Dynamics And Conduction Transformation Of Spirotetramat On Tomato

As a broad-spectrum,high-efficiency and safe pesticide,spirotetramat has a good control effect on pat sucking pests,and it has widely been used on tomatoes.However,there are few reports on the residual digestion dynamics and conduction transformation of spirotetramat and its metabolites in tomatoes.In this research,HPLC-MS/MS methods for the residues analysis of spirotetramat and its metabolites in multiple matrices were established.The methods were used to detect the digestion dynamics and final residue of 10%spirotetramat(OD)in tomatoes.In addition,the laws of absorption,conduction and transformation of spirotetramat in tomato plants were explored by hydroponic,and the effect of mixed application of pymetrozine on it was also researched.The results provided theoretical basics for the safe and efficient use of spirotetramat in the production of tomatoes.The concrete results are as follows:1.The HPLC-MS/MS analysis methods with QuEChERS pre-treatment processes for spirotetramat and its four metabolites,pymetrozine were established.These methods were applied for the quantitative detection of six compounds in tomato roots,stems,leaves,fruits and nutrient solutions.In the concentration range of 0.001?0.2 mg/kg,the matrix matching standard curves of the 6 compounds had good linear relationship,and the correlation coefficient ranged from 0.9957 to 1.000;the LOQ of the methods for 6 compounds were all 0.005 mg/kg;the recovery rate of spirotetramat and its four metabolites,pymetrozine in the five matrices was 70.26%?119.18%,with the RSD of 1.12%?8.61%.The method was efficient and stable,which was suitable for the analysis of high-throughput samples.2.The final residues and digestion dynamics of 10%spirotetramat(OD)on tomato were determined.The digestion dynamics of spirotetramat on tomato complies with the first-order kinetic equation,the digestion equation is C1=0.1154e-0.0621,R2=0.9428,the half-life is 11.18 d,after 7?10 days of application,the residue of spirotetramat was 0.058?0.084 mg/kg,which was less than the MRL value of 1 mg/kg in China.Therefore,it was safe to harvest after 7 days of application with applying spirotetramat twice at a dose of 82.5 g a.i./hm2.3.The absorption,conduction and transformation of spirotetramat in tomato plants were studied by hydroponics.The effects of different application methods and mixed application with pymetrozine on the absorption and conduction of spirotetramat in tomatoes were studied.Spirotetramat applied to the roots was mainly converted into B-enol,B-keto and B-glu,the three metabolites can be conducted upwards;Spirotetramat sprayed on the leaves in tomato plants was mainly converted into B-enol and B-keto,and the two metabolites have weak downward conduction ability.Regardless of the application method,spirotetramat and its metabolites were mainly accumulated in leaves,and mixed application with pymetrozine would promote the transformation of spirotetramat.