The Application Of Microextraction In The Detection Of Pesticide Residues In Tea

With the improvement of people's living standards and the enhancement of health awareness,tea drinks which are good for healthare increasingly popular with consumers.However,the problem of tea safety caused by pesticide residues has attracted increasing attention.In recent years,microextraction pretreatment technology is favored by more and more analytical workers.Under this environment,dispersive liquid-liquid microextraction(DLLME)technology and solid-phase microextraction(SPME)technology have come into being.They have been increasingly applied for the extraction of analytes in various sample matrices due to their simplicity,quickness,low cost and high enrichment efficiency.This work describes the application of two microextraction techniques in the detection of pesticide residues in tea.The full text consists of three parts,the main contents are summarized as follows:1.In this paper,new sample pretreatment techniques were summarized.Importantly,the principle,influencing factors and the application of dispersive liquid-liquid microextraction in food analysis,the principle and the application of headspace solid-phase microextraction in complex sample matricesas well as main techniques for the analysis of pesticide residues were introduced.The background and content of this work were also elaborated.2.A gas chromatography-triple quadrupole mass spectrometry(GC-MS/MS)method for the rapid determination of 7 pyrethroid pesticide residues in tea was developed using dispersive solid-phase extraction and dispersive liquid-liquid microextraction(d-SPE-DLLME)as sample preparation methods.The samples were extracted with acetonitrile,purified with primary secondary amine(PSA)and multi-walled carbon nanotubes(MWCNTs),concentrated into carbon tetrachloride(CCl4),and analyzed by GC-MS/MS.The factors influencing the extraction were optimized by using full fermented black tea matrix.In this experiment,acetonitrile was used as extractant in d-SPE,200 ?L of CCl4 was used as extractant,1 mL of acetonitrile was used as dispersant,and extraction time was 1 min in DLLME.The results showed that the calibration curves of 7 pesticides were linear in the range of 10~500 ?g/kg,with correlation coefficients of 0.9991~0.9999,and the limits of detection ranged from 0.11 to 3.01 ?g/kg.The average recovery ranges of 7 pesticides in four kinds of tea(black tea,green tea,oolong tea and dark tea)at three spiked levels were 82.7~111.8%,75.4~113.6% and 82.6~107.1%,respectively.The relative standard deviations(RSD)were all below 8.6%(n=5).The proposed method is simple and fast with low cost and low detection limit.Twelve commercially availabletea samples were detected by the established method,and 5 pyrethroid pesticides were detected.3.Headspace solid-phase microextraction(HS-SPME)combined with gas chromatography-triple quadrupole mass spectrometry(GC-MS/MS)was used for rapid determination of 9 amide herbicide pesticide residues in tea.Various factors such as the types of extraction coatings,the type of inorganic salt,water consumption,salt dosage,extraction temperature and extraction time in SPME were optimized.The results showed that the calibration curves of 9 amide herbicides were linear in the range of 50~1000 ?g/kg,with correlation coefficients of 0.9925~0.9999,and the limits of quantitation ranged from 1 to 50 ?g/kg.The average recoveries of the 9 pesticides in 4 kind of tea at three spiked levels were 70.3~125.4%,85.2~118.7% and 74.6~113.3%,respectively.The relative standard deviations(RSD)were all below 17.4%(n=5).The method is simple and fast with high sensitivity and good reproducibility,which can meet the detection requirements of 9 amide herbicide pesticide residues in tea.