The Application Of Cloud Point Extraction For Determination Of Melamine In Milk And Organochlorine And Pyrethroid Pesticides Residues In Fruits

Food is a foundation that mankind rely on it for existence and development. In recent years, the food trade develops rapidly and food export has become the important originates of the foreign exchange.But the food security problem gets to be more and more important The chemistry composition in the food is very complicated. The confirmatory multiresidue analysis for organic compounds at trace levels in complex matrixes is required in food analysis. It is quite necessary and of great significance to do the research on determination of harmful residues in foods to break through the technical barriers, smooth flow Chinese food to the world market. The thesis includes two parts:In chapter:Determination of melamine in milk using cloud point extraction-high performance liquid chromatographyThe feasibility of employing cloud point extraction (CPE) as extraction and purification method for the recovery of melamine from milk samples followed by high performance liquid chromatography (HPLC) analysis is demonstrated. The2%(W/V) Triton X-100and2%(W/V) CCI3COOH at temperature100℃and time10min were used for the demulsification of milk. The surfactant PEG-600was used to be as extractant for the extraction of melamine in milk, extracting conditions:13%(W/V) PEG600,0.5%(W/V), Na2CO3,26%(W/V) Na2SO4, equilitration temperature70℃, equilitration time30min. The recovery of spiked melamine in the milk was more than80%, RSD was2.1%, the limit of detection for melamine was0.9mg/kg, lower than the maximum residue limit of China(2.5mg/kg). The results indicate that the method is easer, faster, high sensitivity and produces less pollution.In chapter:The application of cloud point extraction with back-extraction in determination of eighteen organochlorine and pyrethroid pesticides by gas chromatography A method was developed for the determination of organochlorine and pyrethroid pest-icides:hexachlorobenzene, α-BHC, γ-BH, heptachlo, aldrin, β-BHC,δ-BH, heptachlor epocide, α-endosulfan, P,P’-DDE, dieldrin, isoldrin, β-endosulfan, endrinaldehyde, bifenthrin, endosulfan sulfate, fenpropathrin, deltamethrin. Extract these pesticides from apple sample by acetonitrile, employ cloud point extraction (CPE) as purification and concentration method for the recovery of eighteen pesticides from apple sample, then reextract by n-hexane. Using this method to determine these pesticides, the spiked recoveries of15pesticides were63.94%-100.3%, while another3pesticides were under50%; and the relative standard deviations were in the rang of1.60%-7.96%. The limits of detection (LODs) were2×10-5～4.0×10-3mg/kg. This method has been used for detection of multiple organochlorine and pyrethroid pesticides in apple samples, and proved to be cheap, simple and used less organic solvent.