| Food is the most elemental life material of mankind. It is the resource of energy and nutrition which is indispensable to maintain human life and healthy body. The quality of food is direct relate to the health and quality life of mankind, therefore, it is necessary to have a food evaluation. The examination of harmful materials in food is one of the most important content about food analysis. The first link about the test of harmful materials in food is to extract and purify the trace goal compounds from sample. The effection of extraction will give a direct influence on the result of analysis. At present, there are some frequently used chromatography analysis method and technology in food analysis such as Thin-LayerChromatography,Gas-Cliromatography,Liquid-Chromatography,Chroma tography-Mass. All of the methods demand the sample purified, because the exist of great quantity impurities bring about big interference to the result, furthermore, which can lead to the wastage of the instrument seriously. So extraction, condense and purity is very important. Liquid-Liquid Extraction (LLE) is a kind of tradition sample pretreatment method. There are 70 percent of documents which adopt Liquid-Liquid Extraction as a way of sample pretreatment. Recently, a lot of new sample pretreatment technologies have been brought out, such as Accelerate Solvent Extraction(ASE), Microwave Assist Extraction(MAE), Solid Phase Extraction(SPE), Super-Fluid Extraction(SFE), Membrane Extraction(ME), Solid Phase Micro-extraction(SPME), Single Drop Solvent Extraction(SDE). All of these methods have their own advantages and defections. The thesis made a study about three sample pretreatment methods which are solid phase micro-extraction(SPME), headspace(HS) and single drop solvent extraction(SDE) used in the analysis of N-nitrosoamines in beer.First, it made a summarize about Solid-Phase Micro-Extraction(SPME) technology and application according to literature. A Solid-Phase Micro-Extraction (SPME) coupled with Gas Chromatography-Mass analytical method has been developed for determination of N-nitrosodiethylamine, N-nitrosodi-n-butylamine,N-nitrosopropylamine in beer. A polydimethylsiloxane/divinylbenzene coated fiber was used. The experimental conditions, such as extraction time, extraction temperature, stirring speed , ion intensity were optimized. Under the optimum conditions, the linear range was between 12.5 and 250 μ g/L with detection limits of 2.27μ g/L to 8.99 μ g/L. The method was used for determination of trace volatile organic N-nitrosoaminocompounds in beer. The average recoveries of NDBA are 85.5% to 95.5% and RSD was from 6.2 to 8.9%.The new method is solventless, environmentally, useful for rapid monitoring purposes with satisfactory resultSecond, A Headspace coupled with Gas Chromatography-ECD analytical method has been developed for determination of N-nitrosodiethylamine, N-nitrosodi-n-butylamine, N-nitrosopropylamine in beer. The experimental conditions, such as equilibrium tune, equilibrium temperature, stirring speed , ion intensity and the way of extraction were optimized. Under the optimum conditions which is 0.1gNaCl as salting-out agent, gas-liquid phase match 1/1, equilibrium temperature 85℃, equilibrium time 40 min , injection sample volume 0.25ml, the linear range was between 100 and 1500 μ g/L with detection limits of 20μg/L to 40 μ g/L. The method was used for determination of trace volatile organic N-nitrosoaminocompounds in beer. The average recoveries of NDBA are 66.1% to 92.3% and RSD was from 4.2 to 6.9%.The method is solventless, environmentally, useful for rapid monitoring purposes , but the detection limits should be further decreased.Third, Micro-drop Extraction is based on Liquid-Liquid Extraction and come up with combined micro-principle from solid phase micro-extraction as a new separation and collection method. The basic approach of this technology is to put micro-litter even nano-litter degree extraction solvent into the solution which is stirring or flowing, so that it turned the...
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