Determination Of Pesticide Multiresidue In Crops By UPLC-QqQ-MS/MS

In recent years, food safety issues have become the focus of attention, especially pesticide residues in crops, which are closely related to the health of consumers. Therefore, it is urgent to establish a rapid, simple, sensitive, and effective pesticide multi-residue method. This dissertation focuses on pesticide residues in tea and leeks.a rapid and effective multiresidue method has been developed for the determination of18pesticide residues (selected from organonitrogen, organophosphorus, and carbamate pesticides) in tea by ultrahigh-performance liquid chromatography-tandem mass spectrometry. Tea samples were extracted with acetonitrile and purified by a novel multilayer solid-phase extraction cartridge-Cleanet TPT. Eluted with acetonitrile-toluene (3+1, V/V), dissolved in1.50mL acetonitrile and filtered with a0.22μm organic membrane for UPLC-MS/MS analysis. The total analytical time required for chromatographic runs (including sample injection and column equilibration) was14min. Evaluation of the influence of the mobile phase on the ionization efficiency, resolution, and sensitivity was carried out by comparing the acetonitrile-water and methanol-water with different modifiers. The recoveries of all the pesticides varied from70to110%with a relative standard deviation of less than15%. Good linearity was obtained from2to200μg/L for all pesticides, and the determination coefficient for each pesticide was>0.99. Matrix-matched standard calibration was used to reduce the quantitative error, and specific matrix effect was evaluated for the performance of18pesticides in this study.The limit of detection for all targeted pesticides ranged from0.03to1.5μg/kg, which were much lower than the respective MRL established by the EU legislations. Applicability of this analytical approach was confirmed by successful determination of tea samples from different regions of China. This dissertation also have been developed a method for trace level and multiresidue analysis of7pesticides in leeks by ultrahigh-performance liquid chromatography-tandem mass spectrometry. Sample pretreatment conditions (including solvent extraction, solid phase extraction column, eluent, etc) and UPLC-MS/MS conditions were optimized. Leeks were extracted with acetonitrile directly, and purified by amino SPE. Eluted with methylene chloride-methanol (99+1, V/V) and dissolved in methanol-water (1+1, V/V). Methanol-water (1mM ammonium acetate) was chose to be mobile phase, and ACQUITY UPLC HSS T3column was used to make effective separation and rapid detection. This dissertation use matrix-matched standard calibration to compensate matrix effect to finish the accuracy of quantitative analysis, and specific matrix effect was evaluated for the performance of7pesticides in leeks. In addition, multiple reaction ion monitoring mode (MRM) was used to to reduce matrix interference to further improve the accuracy of qualitative and quantitative, which effective solve the problem of trace level and multiresidue analysis for complex matrix leeks. The recoveries of three spiked levels (10,50,100μg/kg) were between81-96%, and the relative standard deviation (RSD) were below10%. Good linearity for standard curves of seven pesticides were found in the concentration range of5-200μg/L, the correlation coefficients were0.9978-0.9996, the limits of detection were0.05-0.70μg/kg, and it was appropriate for confirmatory analysis.