Effects of various binary and ternary supercritical phases on the extraction of polycyclic aromatic hydrocarbons from contaminated soils

Abstract

Polycyclic aromatic hydrocarbons (PAHs) were extracted from two real environmental soil samples using supercritical fluid extraction (SFE) with organic modifiers. The modifiers ( n-pentane, acetone, toluene, dichloromethane, methanol) as well as modifier mixtures (methanol containing acetone, toluene, acetic acid; acetone containing toluene, ethanolamine; n-pentane containing acetic acid) were used in two different concentrations. In general, extraction efficiency increased with reduced polarity of the modifier used and at higher concentrations of co-solvent. Extraction of PAHs from the minor polluted soil with a high content of humic acids was enhanced greatly by the use of modifiers in comparison with pure CO 2 and Soxhlet extraction utilising dichloromethane or n-pentane. The highest PAH yields were received with CO 2 containing 10 or 2 mol% pentane followed by CO 2 with 10 mol% toluene. In contrast, for the soil highly contaminated with mineral oil products but with a low content of humic substances, the extraction efficiency was only increased a little by the addition of modifiers in comparison with pure CO 2 and decreased in comparison with Soxhlet extraction. The results lead to the conclusion that the use of modifiers during SFE is well appropriated to break strong matrix–analyte interactions, like humic acids–PAH interactions in the low contaminated soil. But for soils highly contaminated with aliphatic hydrocarbons, SFE is less suitable, because of the viscosity and solubility of the hydrocarbons for PAHs.