Determination of polycyclic aromatic hydrocarbons from soil samples using selective pressurized liquid extraction

Abstract

A selective pressurized liquid extraction (SPLE) method has been optimized for the determination of polycyclic aromatic hydrocarbons (PAHs) in soil samples. The method comprises a fully automated extraction and on-line clean-up procedure by inclusion of sorbents in the extraction cells. The contributing parameters of SPLE including type of solvent, static extraction time, number of extractions, extraction temperature, nature and amount of sorbents were investigated. The optimal extraction was performed at 70 °C for 10 min (static extraction time) cycled once using n-hexane/methylene chloride (50 : 50, v/v) and the sorbents in the extraction cells were 3 g of alumina and 2 g of silica gel. The collected extracts from the cells, after pre-concentration, were clean enough for direct injection into GC-MS. Validation of the SPLE technique was performed, with the recovery rates for 16 PAHs in the range of 75–103%, and the relative standard deviation (RSD) was generally less than 10%. Method detection limits (MDL) were in the ranges of 0.001–0.080 μg kg⁻¹ for the GC-MS analyses. Finally, the method was successfully used to evaluate the cultivated soils in Beijing, China.