Residual Analysis And Digestion Dynamics Of Metalaxyl, Cyfoamazole And Their Metabolites In Tobacco And Soil

In this paper,a method was developed and validated for the simultaneous determination of metalaxyl-M,cyazofamid,and the cyazofamid metabolite4-chloro-5-p-tolylimidazole-2-carbonitrile(CCIM)by QuEChERS(quick,easy,cheap,effective,rugged and safe)and liquid chromatography with tandem mass spectrometry.And the matrix effects of soil,green tobacco leaves and cured tobacco leaves on metalaxyl,cyazofamid and CCIM were investigated.The method was applied on the residual analysis of metalaxyl-M and cyazofamid in green tobacco leaves,cured tobacco leaves and soil samples after sprayed.The three target compounds were extracted from tobacco and soil samples with acetonitrile containing 0.1%acetic acid,and the extracts were purified using octadecyl silane.The proposed method showed satisfactory linearity(R~2≥0.9985)for the target compounds.The limits of detection and quantification for three analytes in all matrices were 0.006-0.3 mg/kg and 0.02-1 mg/kg,respectively.The average recoveries in green tobacco leaves,cured tobacco leaves and soil were72.91%-98.40%formetalaxyl,76.73%-105.80%forcyazofamid,and74.48%-106.45%for CCIM.The relative standard deviations was between 1.23%and6.99%.The results indicated that the established method could meet the requirements for the analysis of trace amounts of all three analytes in soil and tobacco matrices.The dissipation dynamics and terminal residues experiments of metalaxyl-M and cyazofamid(2%,GR)in tobacco fields were carried out in Hunan and Guizhou provinces,China,in 2016 and 2017.Samples were detected and analyzed by the established detection method based on LC-MS/MS.The results showed that when the pesticides were applied once at dosages of 270 g a.i/ha and 405 g a.i/ha,the terminal residue levels of metalaxyl and cyazofamid in cured tobacco leaves were<1.55 mg/kg and<1.94 mg/kg,respectively.