Application Studies Of Supercritical Fluid Extraction On Pesticide Residue Analysis

Supercritical fluid extraction(SFE) is a new developed technique for extraction .separation and purification. As a pre-treatment of sample, SFE offers better precision, shorter analysis time, and a reduction of solvent usage comparing with traditional extraction methods. SFE were mainly used in the fields of oil, chemical engineering, natural products, food, cosmetics etc. Recently it had been used in environmental protection, macromolecular chemical synthesis, as well as the preparation of special material. In 1986,Capriel successfully put SFE into the practice of pesticide residue analysis. Application of SFE on pesticide residue analysis was seldom studied in China. In this paper the extraction conditions of chlorfluazuron, tebufenozide, cyhalothrin, fenpropathrin, cypermethrin, cyfluthrin and the application of SFE on pesticide residue analysis using chlorfluazuron were studied. In our experiments we did some methodology researches, drew some useful conclusions and accumulated some experience.1. The evaluate methods of extraction efficiency applied in this paper have been proved to be suitable to the research of SFE on pesticides. The quantitative methods were HPLC or GC. According to three indexes to evaluate extraction efficiency(namely: extraction ratio of gross compounds, content of pesticide in gross compounds, recovery of pesticide).2. Celite was used as drying agent, the ratio of Celite and matrix was 1: 2.3. The pattern of SFE was the connection of static and dynamic extraction. Of all the six pesticides, suitable static time was 20min and then followed by dynamic extraction.4. The orthogonal design were conducted with 3 factors and Slevels for chlorfluazuron, cypermethrin, cyfluthrin (the factors were pressure, temperature and volume of CO2) .As to tebufenozide, cyhalothrin and fenpropathrin, orthogonal design were conducted with 5 factors and 41evels(the factors were pressure, temperature, volume of CO2, doses of modifier and static time). The most important factors were respectively obtained. The optimum extraction conditions of six pesticides were determined. To the three indexes of chlorfluazuron, temperature was the most remarkable factors. Modified with methonal(0.08ml/g(nlatrjx))was suitable to the extraction of chlorfluazuron. The trapping solvent was methonal. In a general, the extraction conditions of chlorfluazuron were: pressure 3000PSI,temperature 75 ,volume of CO2 50ml,doses of modifier0.08ml/g(matrix) and static time 20min. The optimum extraction conditions of tebufenozide were: pressure 7000PSI,temperature 60 ,volume of CO21 Oml,doses of modifier 0.04ml/g(matrjx) and static time 20min,the trapping solvent was acetone. The optimum extraction conditions ofcyhalothrin and fenpropathrin were: pressure 5000PSI,temperature 45 ,volume of CO2 25ml,doses of modifier 0.04ml/g(matriX) and static time 20min. The optimum extraction conditions of cypermethrin and cyfluthrin were: pressure 4000PSI,temperature 65 ,volume of CO2 10ml,doses of modifier 0.05ml/g(matrix) and static time 20min and pressure 6000PSI,temperature 45,volume of CO2 30ml,doses of modifier 0.075ml/g(matrjx) and static time 20min.5. The choice of trapping solvent depends on the physical-chemical properties of compounds. The experiments showed the suitable trapping solvent of chlorfluazuron, cyhalothrin, fenpropathrin, cypermethrin and cyfluthrin were methonal, the solvent of tebufenozide was acetone.The application of SFE on pesticide residue analysis has extensive prospects. Although some conclusions were gained in our work, further research is still needed.