Application Of Microwave Absorption Medium To Microwave-accelerated Extraction

In the introduction, the characteristics, toxic and classification ofOrganophosphorus pesticides were reviewed. And the main performances ofmicrowave-assisted extraction were introduced.In chapter2, a new self-designed microwave absorption tube was used inmicrowave-assisted extraction of seven organophosphorus pesticides from four kindsof vegetable samples. The non-polar solvent was used as extraction solvent, and anew portable microwave extraction apparatus was used. By sealing graphite powderin glass tube, microwave absorption tube was made and used to heat samples directly.The extracts were directly analyzed by GC-MS without any clean-up process. Theeffects of some experimental parameters on extraction efficiency were investigatedand optimized.3.00g of sample,25.00mL of hexane and three microwave absorptiontubes were added in the microwave extraction vessel, the extraction was carried outunder425W irradiation power at70℃for8min. The recoveries were in the range of76.5～109.4%and the relative standard deviations were lower than13.1%. And theStudent’s t test was applied. The statistical analysis indicates that the differencesbetween the optimal values and the nearest values for the experimental parameters aresignificant (P＜0.05). So, the selected optimal extraction parameters should bereasonable.In chapter3, a single-step extraction-cleanup method, microwave-assistedmicro-solid-phase extraction (μ-SPE), was developed for the extraction of tenorganophosphorus pesticides in vegetable and fruit samples. Without adding any polarsolvent, only one kind of non-polar solvent (hexane) was used as extraction solvent in the whole extraction step. The μ-SPE device, was prepared by packing activatedcarbon with microporous polypropylene membrane envelope, and used as not only thesorbent in μ-SPE, but also the microwave absorption medium. Some experimentalparameters effecting on extraction efficiency were investigated and optimized.1.00gof sample,8.00mL of hexane and three μ-SPE devices were added in the microwaveextraction vessel, the extraction was carried out under400W irradiation power at60℃for10min. The extracts obtained by microwave assisted-μ-SPE were directlyanalyzed by GC-MS without any clean-up process. The spiked samples were analyzed.The recoveries for the analytes in vegetables and fruits were in the range of92.4～104.4%,92.9～104.6%, respectively. And the relative standard deviations fordetermination in the vegetables and fruits were in the range of1.9～6.2%,1.5～8.7%,respectively. The present method was compared with ultrasonic extraction andhot-water bath extraction.