Application Of Supercritical Fluid Chromatography-tandem Mass Spectrometry In The Determination Of Pesticide Residues In Plant Foods

In recent years,with the rapid development of economy,more and more pesticides has been used on crops,leading to the problem of excessive pesticide residues,which not only has a certain impact on the environment,but also poses a huge threat to people’s food safety.Therefore,an efficient,sensitive,accurate and stable detection method is necessary to deal with the potential threat of the raising of pesticides uses.Through the reliable analysis method,the pesticide residue is monitored,in order to better escort for food safety.At present,there are several sample pretreatment methods,including soxhlet extraction,solid phase extraction,matrix solid phase dispersion extraction,accelerated solvent extraction,and Qu ECh ERS.These methods generally have disadvantages such as cumbersome operation,time consuming,large solvent consumption,and off-line operation.Under Qu ECh ERS approach,acetonitrile(15~20 m L)is used and several steps should be conducted including weighting,extraction,centrifugation,purification,and re-centrifugation.In contrast,online supercritical fluid extraction(SFE)has the advantages of saving organic solvents and simple operation,after weighing the sample into the extraction tank and adding a dispersant with well mixing,the automatic online extraction is performed.The consumption of solvent is less than 5 m L under SFE progress.In addition,with supercritical fluid chromatography tandem mass spectrometry(SFC-MS/MS),consumes less organic solvent than conventional liquid chromatography tandem mass spectrometry,and the analysis efficiency of SFC-MS/MS is higher;unstable or hardly volatile compound can also have a better response.However,there is no research on applying online supercritical fluid extraction-supercritical fluid chromatography tandem mass spectrometry(SFE-SFC-MS/MS)to the analysis of pesticide residues in food.1.In this study,an online SFE-SFC-MS/MS method was established for the accurate qualitative and quantitative determination of 71 common pesticide residues in maize flour and tea.(1)By comparing different SFE extraction conditions and SFC chromatographic separation conditions,the optimal online SFE-SFC-MS/MS conditions were obtained as follow: extraction solvent was super critical CO2 : ethanol(91:9,v/v),static/ dynamic extraction time was 5 min,dynamic extraction velocity was 5 m L/min,weight ratio of dispersant anhydrous magnesium sulfate and sample was 5:1(w/w),SFC modifier was 0.1% formic acid methanol,gradient elution,flow rate was 1.5m L/min,back pressure regulator A(BPRA)pressure was 14.8 MPa,column temperature was 40 ℃,post-column compensation solvent was 0.1% formic acid methanol with flow velocity of 0.05 m L/min.(2)In addition,the method had good linearity,with R2 > 0.99.The recoveries of maize flour and tea were in the range of 71.16%~125.08% and 65.8%~123.96%,respectively.The relative standard deviations(RSDs)were in the range of 1.94%~30.51% and 2.31%~30.09%,respectively.The limits of detection were 0.003~2.77 μg/kg,0.01~3.6 μg/kg,and the limits of quantification were 0.01~8.41 μg/kg,0.02~10.92 μg/kg,respectively.(3)The analysis was completed within 32 min.In the actual sample,four compounds were detected in maize flour and seven in tea.The results showed that this method was sensitive and efficient,and could be applied to the monitoring and determination of pesticide residues in maize flour and tea substrates.2.In addition to the online SFE-SFC-MS/MS method,the present study conducted a precise qualitative and quantitative analysis method for 35 commonly used pesticide residues in maize flour based on LC-MS/MS and SFC-MS/MS coupled with Qu ECh ERS extraction-matrix dispersion solid phase extraction(d SPE)or automated microsolid phase extraction(μSPE)purification.(1)The recovery rates of 35 pesticides were compared between d SPE with different PSA dosage and μSPE,and the optimal pretreatment method was selected.(2)The optimal SFC-MS/MS conditions were obtained by comparing the different column temperatures,the pressure of the post-column pressed regulator(BPRA),the type of modifier,the type of compensating solvent and the flow rate.(3)Based on the unified pretreatment method,the qualitative and quantitative methods for 35 common pesticides in maize flour were established on SFC-MS/MS and LC-MS/MS,respectively.The results indicated that the limits of detection and linearity of 35 pesticides on LC-MS/MS and SFC-MS/MS as well as the recoveris and RSDs were good.The current approach met the precise qualitative and quantitative analysis of corresponding pesticides.In addition,the three-level recovery and relative standard deviation based on the automated μSPE method were good,which could be used as an effective supplement to the conventional d SPE purification.