Supercritical Fluid Extraction and Its Application to Environmental Analysis

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Abstract
Sand, spiked with 41 organochlorine pesticides and 47 organophosphorus pesticides, is extracted with supercritical carbon dioxide at various pressures and temperatures, and the recoveries are determined. Two standard reference materials certified for polynuclear aromatic hydrocarbons are extracted under supercritical conditions, and the data are compared with the certified values which have been determined by conventional extraction techniques. There is a large discrepancy between the resulting data and t he certified values. To explain the discrepancy, a preliminary method optimization study is conducted in which the influences on recoveries of seven variables are investigated. The study allows estimation of the main effects of the seven variables; however, the authors could not test the statistical significance of any of these effects. The results from the preliminary method optimization experiments indicate that, under the conditions used, recovery is most affected by extraction time and extraction pressure, followed by moisture content of the material and sample size. Finally, the approximate costs associated with setting up and using a supercritical fluid extraction system in an analytical laboratory are presented and are compared with those for Soxhlet extraction.