EXTRACTION OF POLYCYCLIC AROMATIC HYDROCARBONS FROM SOIL USING WATER UNDER SUBCRITICAL CONDITIONS

Abstract

Water under subcritical conditions (250°C, 4100 kPa) was used to extract polycyclic aromatic hydrocarbons (PAHs) from a Mexican hydrocarbon-contaminated soil. Extraction was carried out by continuously circulating the solvent through the sample contained in an extraction cell. After extraction, the non-extracted PAHs were eluted from the soil and then analyzed by high performance liquid chromatography. The elution and subsequent analysis were carried out by directly coupling the extraction cell, through a switching valve system, to a liquid chromatograph. The elution and analysis process takes place in a closed system that allows a fast, precise, and highly sensitive quantification of the studied compounds. Additional extraction experiments with spiked samples (silicon dioxide and nonpolluted soil) were carried out in order to asses the performance of the method. Extraction recoveries ranged from 95 to 100% with an average uncertainty of ±1.2%. In some cases it was possible to quantitatively extract PAHs at concentrations as high as 8522 mg· kg − 1 .