Supercritical fluid extraction for the determination of petroleum hydrocarbons in soil

The supercritical fluid extraction (SFE) of petroleum hydrocarbons (PHCs) was carried out spiking a clay-sand soil with saturated and aromatic fractions from crude oil. The effect of acetone concentration in the supercritical fluid acting as a modifier was also investigated. The best recoveries of PHCs close to 70-100% were obtained at 80 degrees C and 227 arm, corresponding to a fluid density of 0.65 g/ml of pure CO2, in the presence of 5% (v/v) acetone. The presence of the polar modifier (5%) improved the extraction of the aromatic fraction. Higher concentration of modifier (10%) decreased the extraction efficiencies of both saturated and aromatic fractions. The recovery of the aromatic compounds were proportional to the increase of analyte concentration in the spiking solutions. A combination of size-exclusion and adsorption effects seems to be involved and this would account for the higher recovery of low- and high-molecular-mass n-alkanes as compared to those of the mid ones. (C) 1999 Elsevier Science B.V. All rights reserved.