SFE of an Organophosphorous Compound from Soils with Capillary GC Analysis

The supercritical carbon dioxide extraction of an organophosphorous compound from several matrices is investigated. The effects of extraction parameters are studied using spiked filter paper as a model sample matrix. Recoveries are shown to increase with fluid density and extraction temperature. Faster extractions can be achieved by increasing the flow rate, but higher flow rates lead to losses in the collection step. Poor solute trapping also occurs when the trap temperature is held above 45°C. Supercritical carbon dioxide is effective in removing the solute molecules from fresh spiked soils (average recoveries greater than 85% in 15 min). However, dehydration of the soil samples in a fume hood results in lower recoveries with pure CO2, especially for soils with a high surface area (sedimentary clay and silt). Addition of methanol directly to the soil sample enhances both the extraction rate and precision of the supercritical fluid extraction method. A short static period (5 min) prior to initiation of dynamic supercritical fluid extraction seems to have no influence on extraction recoveries.