Degradation Dynamics And Final Residue Of Imidacloprid And Metabolite 6-CNA

In this paper,the degradation dynamics and final residue of imidacloprid and its metabolite 6-CNA were detected,and the degradation rate of imidacloprid by oligomeric acid and wood vinegar was studied.The second chapter establishes the analytical method of imidacloprid and its metabolite residues in corn and soil.Imidacloprid and its metabolite 6-CNAwas extracted by acetonitrile,and 4gmagnesium sulfate and 1g sodium chloride was sequentially added into the mixture after vortexextraction.Then 1.5mL supernatant was used for sample purification.For cleaning-up,150mg magnesium sulfate and 20mgGCB were used for maize plant and seed,while 150mg magnesium sulfate and 40mgC₁₈ were used for soil samples.Then the sample solutions were filtered,determined by HPLC-MS/MS with 0.2%formic acid and methanol as mobile phase,and gradient elution was used for the analysis.The limit of detection?LOD?and limit of quantitation?LOQ?were 1×10^-11g and 0.01mg/kg,respectively,and the recoveriesof imidacloprid and metabolite 6-CNA in maize plants,seeds and soil were in the range of 70%¹10%with the relative standard deviation ranged from0.5%to 6.8%.In the third chapter,the study on the degradation dynamics and final residues of imidacloprid and its metabolite 6-CNA in maize plants and grains indicatedthat the dissolution rate of imidacloprid and its metabolites in maize plants was faster,and it is in accordance with the first order kinetic equation.600g/L imidacloprid suspension seed coating agent was applied 1 times according to 1.5 times the recommended dose.For Liaoning test field,the half-life of the target insecticide was 6.6d for2016 and 7d for 2017,respectively.For Shandong test field,the half life was 8d for 2016,and there was no half life data for 2017.Forfinal residue study,and the residue of imidacloprid and its metabolite 6-CNA in plants,green seedsand mature seeds were all below LOQ.In the fourth chapter,the degradation dynamics and final residues of imidacloprid and metabolite 6-CNA in soil showed that the degradation rate of imidacloprid and its metabolites in the soil was slower than that in the plant.There was no half life data in two years forLiaoning test field.The half life forShandong test field was 23.1d for two years?2016 and2017?.After the final residue test,the soil samples were collected during the harvest period of maize.After testing,the residue of the target components in Liaoning soil samples was less than the LOQ value;the residue of the soil samples in Shandong was more than that of the LOQ value 0.01mg/kg.The fifth chapter investigated the influence of the different additives on the degradation rate of the analytes.The results showedthat the half-life of the combination of imidacloprid andoligomeric acid,the combination of imidacloprid and wood vinegar and oligomeric acid,and the combination of midacloprid and wood vinegarwas3.63 d,4.95 d,5.17 d,respectively,while the half life of imidacloprid alone is 9.76 d.The degradation rate of imidacloprid andoligomeric acid was faster than that of the other three combinations.The sixth chapter summarizes the all experiment in the paper,and indicates the innovation of this paper.The establishment of the analyticalmethod is discussed,and the effect of wood vinegar and oligomeric acid on the degradation rate of the analytes is investigated.The future research of imidacloprid residue analysis was also explored.