Research Of Meltireside Screen Method In Vegetables And Fruits

The analysis of pesticide residues in food which harm human health andinfluence environment safety is one of the important research duties to chemicalanalysts. But the complexity of the determination system and ultratrace componentshave brought great difficulties to fast separation and accurate measurement for thetask. At present, development of the fast, effective, sensitive multi-residue detectionmethods for pesticides residues analysis is the focus of study in the world.In this paper, a fast-detection GC(LC) method is proposed, which can detect 102pesticides in vegetables and fruits. Pesticides are extracted from samples withacetonitrile and the extraction are cleaned up using SPE(Florisil,NH2), and then, thecompounds are divided into different groups according to their differentcharacteristics and finally the analysis is carried out with special detector.Good linear and lower limits of detection are obtained, the linear range arebetween 0.01 ～ 1.00 mg/L, correlation coefficients are better than 0.990. Fororganophosphorus pesticides, the limits of detection are all between 0.0062-0.1280mg/kg except for trichlorfon, mean recoveries between 70.6%～125.3 %, while therelative standard deviation (RSD%) values between 0.1 %～19.7%, except forphoxim which hasn't been detected.In the detection of organochlorine and pyrethroidpesticides, the limits of detection are between 0.0029～0.0979mg/kg, mean recoveriesbetween 71.0%～126.3%, RSD% values between 0.1 %～20.5 %;In the detection ofcarbamate pesticide, the limits of detection are between 0.0050～0.0580mg/kg, andmean recoveries are between 82.3%～125.1%, RSD% values are between 0.3 %～27.9%.Furthermore, the GC-MS-SIM method are also developed for the analysis of 101pesticides residues in vegetables and fruits in this paper. Through the investigation ofdifferent condition such as gas flow,temperature program and ion fragments groupingand etc., the optimum GC-MS analytical mode has been chosen. The extraction ofpesticides are with the employment of acetone and dichloromethane,and theextraction are cleaned up using SPE (ENVI-Carb) cartridge. In the SIM mode, thelimits of detection are between 0.003mg/kg～0.200mg/kg, mean recoveries arebetween 74.3%～122.7%,RSD values are between 4.3%～20.3%, which can reachthe requirement. And the determination to all the pesticides and their isomers in 56minutes shows the higher selectivity and sensitivity of this method. This method isable to meet the needs of the pesticide residue's test and monitoring analysis fordomestic and export vegetables, fruits and other agro-products.And after verification,the method can be extend application to other products.Aiming at the high cost and import-dependence of the SPE(Florisil,GCB)cartridge, a comparative experiment is made between the domestic and foreign SPEcartridge. The results show that, for the samples which have low pigment content suchas tomato, the domestic SPE (florisiil)'s efficiency is close to foreign;but for thesamples which have more pigment content such as cole, the domestic SPE's efficiencyis a little worse than foreign that, but its mean recoveries, RSD values and etc. stillmeet the requirement, so it can replace the import product.However, the domestic SPE(GCB) catridge contains many impurities including alkane,ketone,amine and etc.,andhave no ample specific surface area and adsorbability to impurities. These impuritieswill interfere the result of experiment in the scan mode by GC-MS.