Extraction of organophosphorus pesticides from soil by off-line supercritical fluid extraction

Abstract

Supercritical fluid extraction (SFE) conditions were optimized for the isolation of organophosphorus pesticides (OPPs) from soil. Results using pure carbon dioxide and carbon dioxide modified with acetone, ethyl acetate or methanol were compared in terms of recoveries, extraction rates and matrix effects. Despite the good solubility of the OPPs in pure CO₂, the addition of methanol was necessary to achieve high recoveries (90%) when spiked soil was extracted. The extent to which matrix effects, which probably cause the decrease in recoveries, occur depends on both the analyte polarity and the spiking method used. Similar extraction efficiencies were achieved by adding microlitre amounts of the modifier directly to the soil in the extraction cartridge and by using a pre-mixed gas cylinder. SFE of OPPs in soil was compared with solvent extraction.