Nordic laboratory intercomparison of supercritical fluid extraction for the determination of total petroleum hydrocarbon, polychlorinated biphenyls and polycyclic aromatic hydrocarbons in soil

Two developed supercritical fluid extraction (SFE) methods [one for the determination of total petroleum hydrocarbon (TPH) and polychlorinated biphenyls (PCBs), and one for polycyclic aromatic hydrocarbons (PAHs) and creosote components in soil] were evaluated in a Nordic laboratory intercomparison study with 11 participating laboratories. The interlaboratory comparison showed that excellent recoveries can be obtained with SFE for PAHs and PCBs compared to the solvent extraction. For the TPH, the recoveries were significantly higher than those achieved with solvent extraction. The accuracy, expressed as the relative standard deviation, was higher than expected (generally 8–25% for PAHs, 6–20% for PCBs and less than 18% for TPH with a few very high values, especially for PCBs), but not different from the other intercomparison studies. Difference between liquid- and solid-phase collection in SFE was found to be significant only for more volatile PAH components such as naphthalene and fluorene. For PCBs and TPH, there were some variation in the results obtained with the two trapping methods.