SUPERCRITICAL-FLUID EXTRACTION OF BOUND PESTICIDE-RESIDUES FROM SOIL AND FOOD COMMODITIES

The use of supercritical carbon dioxide with and without methanol as a modifier to extract bound C-14 pesticide residues from soil, plants, and wheat samples is described. These residues cannot be extracted and detected by methods devised for routine analysis of pesticides and/or metabolites in biological and environmental samples. The C-14 material extracted was trapped in methanol, radioassayed, and then analyzed by various chromatographic techniques. Optimal supercritical fluid extraction conditions for extraction were obtained for each pesticide by varying the temperature, pressure, and amount of modifier. Supercritical carbon dioxide modified with methanol improved the recovery of bound C-14 residues from soil and plant samples. Supercritical methanol was found to be less efficient than supercritical carbon dioxide or methanol-modified supercritical carbon dioxide for the extraction of bound pesticide residues. Analysis of the extracts indicated that the C-14 bound residues in soil, plants, and wheat samples were present in the form of parent compounds and/or metabolites.