Studies On Sample Pretreatment Methods For The Determination Of Organophosphorus Pesticide Residues In Vegetables

This paper can be devided into four sections.Section one: The research progress pretreatment methods to detectpesticide residues in vegetables samples. This section briefly introduced theclassification of pesticides, the present situation of pesticide residues, thedetection method of pesticide residues, and pre-treatment methods ofpesticide residues. And traditional classical pre-treatment was compared withQuEChERS method to analyze the advantages and disadvantages of thetraditional pre-treatment methods.Section two: The recoveries of chlorpyrifos in vegetables weredetermined by national standard method. By using GB method fororganophosphorus pesticides to determine the recoveries of chlorpyrifos invegetables, learn more about the traditional pre-treatment methods.1. GC and GC-MS determination were Compared. By measuringchlorpyrifos standard curve, comparing the instrument detection limit,precision, make evaluations between GC-MS detector and characteristicdetector of gas chromatography.2. We measured chlorpyrifos recoveries in rape, spinach, celery,cucumber by using national standard method, and compared the recoveries.Section three: The effects of cellulose and protein on chlorpyrifosrecovery were determined. By determining chlorpyrifos extraction rate afteradding cellulose, protein in organic solvents-aqueous phase, the effects ofcellulose, protein on chlorpyrifos recoveries were studied. And by thedetermination of the different vegetables in water, protein content, we triedto compare the protein content of different vegetable matrix and to identifythe factors of chlorpyrifos recoveries.1. Extraction rates of chlorpyrifos in organic solvents-aqueous phasewere determined. By changing the experimental conditions, adding soyprotein and cellulose, we studied the effects of protein and cellulose on the extraction rate of chlorpyrifos.2. Moisture and protein content in vegetables were determined. Wedetermined moisture, protein content of rape, spinach, cucumber, eggplant,celery, and compared the differences between the vegetables.3. Looking for relationships between chlorpyrifos recoveries andvegetable protein content, we tried to find if vegetable protein can affectchlorpyrifos recovery.Section four: Pretreatment methods of pesticide residues in vegetableswere tried to improve. The traditional method of pre-treatment, comparedwith QuEChERS method, has many shortcomings, and don’t suit for rapiddetection of pesticide residues contemporary, so in this experiment we usedchlorpyrifos, dichlorvos as example, to improve the national standardmethod.1. Pretreatment methods for chlorpyrifos in celery were studied. Weimproved pretreatment methods by using different solvent, simplifying theexperimental procedure, improving chlorpyrifos recoveries, and detectionefficiency. Eventually, the average recoveries of chlorpyrifos were>90%,RSD was <10%, and the detection limit was <0.005mg/kg.2. Pretreatment methods for dichlorvos in celery were studied.Petroleum ether as extraction solvent, can not be effective extraction ofdichlorvos, therefore, we selected the QuEChERS method, to determinedichlorvos recoveries. Eventually, the average recoveries of chlorpyrifoswere>85%, RSD was <10%,and the QuEChERS method can meet thetesting requirements.