Determination Of Pesticide Residues In Foods Using Liquid Chromatography-Triple Quadrupole-Linear Ion Trap Mass Spectrometry

In agricultural production,the widespread uses of pesticides have caused a series of negative impacts.As pesticides are bioaccumulative,long-term accumulation can harm human health and the environment.Therefore,pesticide residue detection has become a hot topic in current research.In order to ensure food safety,many countries and organizations have established maximum residue limits(MRLs)for pesticides in agricultural products and use this standard as a basis for regulating the use of pesticides.With the development of science and technology,many pesticide residue detection instruments have emerged.Among them,liquid chromatography-triple quadrupole-linear ion trap mass spectrometry(LC-QqLIT-MS/MS)is a powerful detection technique for pesticide residue analysis due to its high sensitivity and high selectivity,adding qualitative accuracy in residue detection.In this study,the method of pesticide multiresidues in foods was established using liquid chromatography-triple quadrupole-linear ion trap mass spectrometry.The main researches are presented as following:The first chapter is mainly overview the pretreatment methods and detection techniques commonly used in the detection of pesticide residues.The solid-phase extraction(SPE),solid-phase microextraction(SPME),matrix solid-phase dispersion(MSPD)and QuEChERS(quick,easy,cheap,effective,rugged and safe)methods are introduced in detail as well as detection technologies,including liquid chromatography separation,triple quadrupole-mass spectrometry and triple quadrupole-linear ion trap mass spectrometry.The second chapter developed a simplified pretreatment method.The method based on the advantage of QuEChERS and microwave-assisted heating method to extract and purify the leek,ginger,garlic,tomato,yam,and corn samples.Chromatographic separation on a C18 column was achieved by gradient elution with water containing 0.1%formic acid and methanol.Determination of the analytes was achieved by triple quadrupole-linear ion trap mass spectrometry.Multiple-reaction monitoring(MRM)was used to quantify and information-dependent acquisition(IDA)was used to trigger enhanced product ion scans(EPI)for identification compounds under low concentration(near LOQs)and the absence of qualitative ion.For complex matrices,multistage mass spectrometry(MS3)was investigated to obtain lower limits of detection(LODs)and the matrix effect was reduced to between-10%and 10%.Mean recoveries for 26 analytes ranged from 70.0%to 120%with relative standard deviations(RSDs)in the range of 0.2%to 10.0%.Calibration curves(1-100 ng/mL)showed good linearities with correlation coefficients(r)higher than 0.99.The limits of detection(LODs)and quantification(LOQs)were in the range of 0.02 to 5.0 ?g/kg and 0.07 to 16.7 ?g/kg,respectively.The MRM-IDA-EPI and MS3 were successfully applied to determine multiresidue pesticide near LOQs level in 44 samples purchased from local markets in Jinan(Shandong,China).The third chapter developed a rapid,sensitive and reliable method for the determination of fipronil and its metabolites in eggs.This method was developed based on modified QuEChERS pretreatment procedure and ultra-performance liquid chromatography-triple quadrupole-linear ion trap mass spectrometry(UPLC-QqLIT-MS/MS).The proposed multistage mass spectrometry(MS3)method provides sufficient sensitivity and excellent reproducibility.The four analytes were separated by a Waters ACQUITY UPLC(?)BEH C18 column and detected by AB Sciex QTRAP(?)5500.The mean recoveries for the four analytes ranged from 90.7%to 105%with relative standard deviations(RSDs)of 0.7%to 4.9%.The calibration curve showed a good linearity within the concentration range of 0.05 to 20 ng/mL.The correlation coefficients(r)were higher than 0.999.The limits of detection(LODs)obtained from the experimental results for fipronil,fipronil-sulfone,fipronil-sulfide,and fipronil-desulfinyl were 0,06,0.02,0.05,and 0.04 ?g/kg,respectively.The MS3 method was successfully applied to detect fipronil and its metabolites in 60 egg samples purchased from Chinese supermarkets,and wholesale markets.