Residue Analysis Of Chlorpyrifos, Imidacloprid And Imidacloprid Metabolites On Wheat

Chlorpyrifos and imidacloprid were widely used to control the prickly mouth pests,such as aphids,whitefly or thrips,on rice,wheat,corn,cotton,potato,and other crops.However,imidacloprid could convert into five metabolites and part metabolites had higher activity than their parent compound,which need to be monitored to ensure the safety of humans and environment.This research aims to establish a method for the simultaneous determination of chlorpyrifos,imidacloprid and imidacloprid's five metabolites in wheat and soil by liquid chromatography with tandem mass spectrometry?LC-MS/MS?.The dissipation dynamics and terminal residue of chlorpyrifos imidacloprid in wheat and soil were also detected at three location in two years,in order to provide data support for the safe application of chlorpyrifos and imidacloprid in wheat.The samples were extracted with acetonitrile?containing 0.5%formic acid?as extraction solvent.After votexing and centrifuging,the extracts were purified by 50mg of anhydrous MgSO₄.The analytes were separated on an Agilent XDB-C₁₈?150×4.6 mm i.d.,5?m?column and showed peaks within 6 min.Satisfactory linearity?R²?0.9965?of the method was obtained for all analytes,the quantitative limit and detection limit are 0.005-2 mg/kg and 0.001-0.666 mg/kg,respectively.Average recoveries were 72.85%–81.25%for chlorpyrifos,78.54%–84.70%for imidacloprid,73.83%–81.03%for imidacloprid olefin,71.47%–80.61%for 5-hydroxy imidacloprid,71.79%–81.32%for imidacloprid urea,70.42%–82.20%for imidacloprid-NTG and70.91%–82.46%for imidacloprid 6-chloronicotinic acid in wheat and soil materices.The intra-day and inter-day relative standard deviations were less than 8%.The method was developed and validated to simultaneously determine chlorpyrifos,imidacloprid and imidacloprid's metabolites in soil,wheat grain and wheat straw matrices.The results demonstrated that some dissipation data of chlorpyrifos and imidacloprid in soil and wheat plants were followed with the first-order kinetic equation.The half-lives were 4.2-9.2 d for chlorpyrifos and 6.1-7.1d for imidacloprid.For midacloprid metabolites,the dissipation data were irregular and the dissipation curve could not be calculated.The terminal residues of seven analytes in the three matrices was<0.005-2 mg/kg and the terminal residues of chlorpyrifos and imidacloprid in wheat grains were lower than the maximum residue limit of 0.05 mg/kg set by China?GB 2763-2016?.