Accelerated Solvent Extraction:  An Evaluation for Screening of Soils for Selected U.S. EPA Semivolatile Organic Priority Pollutants

Abstract

Accelerated solvent extraction (ASE) was evaluated as a possible rapid, low solvent replacement for Soxhlet and bath sonication/shaking extraction in established soil screening methods. A spiked uncontaminated clay loam and soils contaminated with organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons (PAHs) were extracted with 1:1 dichloromethane/acetone. Extracts were analyzed by gas chromatography with mass spectrometric detection in selective ion monitoring mode. For the spiked soil, ASE recoveries were higher than those from Soxhlet extraction for most analytes and generally close to 100% at the 4 and 20 mg/kg levels. At the 0.4 mg/kg level, background peaks caused significant interference for both techniques. This was a greater problem for ASE as the method blank gave a more crowded, complex chromatogram. For the OCP soil, ASE gave higher results than Soxhlet but lower results than bath sonication/shaking, for which a more effective solvent for OCPs was used. For the PAH soils, ASE recoveries were equivalent or superior to bath sonication/shaking, with ASE giving approximately double the total PAH content for matrices containing small stones and/or coal. ASE would be a suitable replacement for existing extraction methods; however, more work is required to reduce background interference.