Study Of Retention Analysis Of Pesticides In Food With Gas Chromatography

The first step of retention analysis is to extract and clean up the trace pesticides. It has an direct effect on the accuracy of results. At present, the common methods, for example,Thin-film Chromatography,Gas Chromatography, liquid Chromatography and Gas Chromatography-Mass Spectrum, require analysing the purer samples. The complicated matrixes will interfere with the retention analyses and damage the instruments. So sampling, concentraction and purification are important prepraration steps in the retention analyses of pesticides. Liquid-Liquid Extraction is a typical and traditional method of preparation that deals with complicated samples. Now it is still used in 70% retention analyses of pesticides. Recently, lots of new techniques of prepraration have appeared, such as, Acceleration Solution Extration(ASE), Microwave Assisted Extraction (MAE), Supercritical Fluid Extraction (SFE), Solid Phase Extraction(SPE), Solid Phase Microextract ion (SPME), Single Drop Extraction(SDE) . These techniques have respective advantages and shortcomings . This thesis makes systematic research in the aspect of Liquid-liquid extraction, Solid Phase Microextract ion and Single Drop Extraction.In the first place, This method aims at the Gas Chromatography method coupled with Liquid-liquid extraction with a electron capture detector of rapid detection of prochloraz and its degradation products in orange of Wuhan and Guangzhou. Using this simple and effective method, Many samples may be treated at one time without large quantities of glassware and solvent. Therefore it has more practical advantages than the previous methods. The rang of calibration curve is 0.05-2. 50mg/l, and the fortified recoveries are 81. 5-96.0%. At the same time, the rule of degradation is studied The results are as follows: (1)The orange are dipped in the1000mg/l concentration, the retention amount of the whole fruit gets 1.21-1.52mg/kg after 30 days, and the half life of the whole fruit is 69.3-88.6 days; (2) The orange are dipped in the 500mg/l concentration, the retention amount of the whole fruit gets 0. 69-0. 73mg/kg after 30 days, and the half life of the whole fruit is 55.5-57.5 days; Detection limit of this method are 0.002mg/kg. The data obtained are able to supply the advice for the safe application of prochloraz in Chinese orange.Then, this part sums up the application of Solid-phase microextration in the retention analysis of pesticide, and use SPME coupled with Gas Chromatograph and a flame photometric detector in phosphorous (GC-FPD)mode of rapid detection of organophosphorus insecticides residues in vegetable. The samples were diluted with water for the sake of reducing the interruption caused by vegetable matrix. Using this rapid and effective method without solvent, better recoveries ,better precisions and low Detection limit were obtained. At the same time, SPME was compared with the routine method, Liquid-liquid extraction, and the comparison result is that SPME is suitable method to the organophosphorus insecticides with the shorter degradation time.Lastly, The part developed a new technique, called a Single drop extraction, to analyse organochlorinated pesticides in honey. This method discussed the varied correlative factors about Single-drop extraction. The rang of calibration curve is among 0.05-2. 50mg/l, Better recoveries of BHC in the honey were obtained under the optimistic conditions. The detection limit of the 4 iso-compounds of BHC has the rang of 0.56-L50ug/kg. Single-drop microextraction is an extraction technique that only need several microliter organic solvent(l-2ul). It can overcome the shortcomings of SPME when organochlorinated pesticides were analysed. The experimental results show a single drop extraction is acceptable method of retention analysis to BHC pesticides in honey.