Study On Monitoring Technique Of Multi-pesticide Residues And Degradation Of Imidacloprid In Leek

In order to control pesticide residues in leek, this research was established a detection methold and sduy the residue behavior of imidacloprid in leek. Established organophosphorus and neonicotinoid two kinds of pesticide residues technology method by ultra high performance liquid chromatography-tandem mass spectrometry (UPLC/MS/MS), and this study design digestion dynamics and final residues of imidacloprid in leek, the main research results are as follows:A method was developed for simultaneous determination six organophosphorus pesticide residues in leek. The samples were extracted with acetonitrile, clean up by GCB-SPE column, detected by ultra liquid chromatography-mass spectrometry under multiple reaction monitoring mode, and quantitated by matrix-match standard solution. The results show that:six kinds of pesticide is characterized by the enhanced effect of ion. In addition concentration of 0.005?0.01?0.05 mg/kg, the average recoveries of the insecticides ranged from 69.1%?110.4%, with the relative standard deviation was 1.1%?8.6%. The limit of detection for these six pesticides in leek was 0.003 ng, and the limit of quantification was 0.005 mg/kg. The method is simple, quick and with high performance. It could be applied for determination in leek samples. And leek samples from supermarket were monitored by established method, methamidophos, methyl parathion, parathion, phoxim pesticide residues were not detected. The range of phorate residues was 0.005?0.087 mg/kg, the range of chlorpyrifos residues was 0.005-0.171 mg/kg.A method was developed for simultaneous determination of six neonicotinoid pesticides residues in leek. The sample were extracted by acetonitrile, the dispersive solid-phase extraction (GCB 10 mg, PSA 50 mg, C18 50 mg, MgSO4 50 mg) purification, detected by UPLC-MS/MS in multiple reactive ion monitoring mode (MRM), combined with the matrix matching standard curve method, Results show that:The results show that: six kinds of pesticide is characterized by the enhanced effect of ion. With the addition concentration of 0.005?0.01?0.05 mg/kg, the average recoveries of the insecticides ranged from 73.5%?101.3%, with the relative standard deviation was 1.1%?8.6%. The limit of detection for these six pesticides in leek was 0.003 ng, and the limit of quantification was 0.005 mg/kg. The method is simple, quick and with high performance. It could be applied for determination in leek samples.A method was developed for determination imidacloprid residues in soil. The sample were extracted by acetonitrile, the dispersive solid-phase extraction purification(PSA 50 mg, C18 50 mg, MgSO4 100 mg), detected by UPLC-MS/MS in multiple reactive ion monitoring mode (MRM), combined with the matrix matching standard curve method, Results show that:with the addition concentration of 0.005?0.01?0.05 mg/kg, the average recoveries of the imidacloprid ranged from 86.2%-93.9%, with the relative standard deviation was 2.5%?7.9%. The limit of detection for imidacloprid in soil was 0.003 ng, and the limit of quantification was 0.005 mg/kg. The method is simple and reliable, which met the requirement of pesticide residues analysis, and could be applied for determination in soil samples.In 2014 year, a field experiment was conducted to reveal the residual dynamics and final residue of imidacloprid after imidacloprid 10% GR applied in leek in Shandong of China. Dissipation dynamics of imidacloprid in leek test results show that:leek and soil could meet the requirements of the first-order chemical reaction kinetic equation, the equation in leek and soil is Ct=0.434e-0.362t and Ct=1.6234e-0.183t respectively, the correlation coefficient (r) respectively 0.978 and 0.906, the half-life of imidacloprid in leek and soil were 1.9 and 3.8 d. With the final residue test that the leek was root-irrigation 1 to 2 times with imidacloprid in the dosage of 225 g a.i./ha2 and 337.5g a.i./ha2, each spraying intervals for seven days, the result showed that when the last application was done at 14 days, the terminal residues of imidacloprid in leek below 0.017 mg/kg, the final residues in the soil of the range of 0.054?0.157 mg/kg, By these results, we recommended that the rational use of imidacloprid in leek field was that imidacloprid was root-irrigation in leek with a dose of 337.5 g a.i/hm2 for 2 times at most, the safe period of imidacloprid in leek could be set as 14 d.