Influence of solvent and soil type on the pressurised fluid extraction of PAHs

Pressurised fluid extraction (PFE) of polycyclic aromatic hydrocarbons (PAH s) from a certified reference material (CRM) 524 has been firstly optimised following a central composite design. The instrumental parameters of the P FE (pressure, temperature, extraction time and number of solvent cycles) we re studied in order to obtain maximum extraction yields. Neither pressure n or extraction time or temperature seemed to have any significant effect on the extraction yield, therefore one extraction cycle was enough to exhausti vely extract all the PAHs from CRM 524. Once the instrumental conditions we re established, the extraction yields obtained with eight different solvent s or solvent mixtures [acetone, dichloromethane, acetonitrile, acetone-dich loromethane (1 + 1 v/v), acetone-isohexane (1 + 1 v/v), isohexane, methanol and toluene] from the CRM 524 were compared and showed that the best recov eries were obtained with acetone-isohexane (1 + 1 v/v). Finally, the effect of sand, silt, clay and the organic matter content of soil was investigate d with respect to recovery of PAHs by PFE with different solvents or solven t mixtures for aged soil samples. In this case, eight soils with different sand, silt, clay and organic matter contents were slurry spiked with PAHs a nd aged for 19 days. Three aliquots of each slurry spiked soil were extract ed with the previously mentioned solvents and the results were studied by m eans of principal component analysis (PCA) of the whole data set (soil comp osition, solubility parameter of the solvent and recoveries of all PAHs) an d partial least squares (PLS). Clay and organic matter content and the squa red solubility parameter have the highest correlation with the recovery of PAHs from soil samples.