Effects of temperature and pressure on supercritical fluid extraction efficiencies of polycyclic aromatic hydrocarbons and polychlorinated biphenyls

Three certified reference materials, polychlorinated biphenyls (PCBs) from river sediment, polycyclic aromatic hydrocarbons (PAHs) from urban air particulate matter, and PAHs from highly contaminated soil, were extracted with pure CO[sub 2] at conventional (50[degrees]C) and high (200[degrees]C) temperatures. At 50[degrees]C, raising the extraction pressure (350--650 atm) had no effect on extraction efficiencies from any of the samples. High recoveries were obtained in 40 min from the highly contaminated soil regardless of temperature. However, PCBs from sediment and the PAHs from air particulates were efficiently extracted only if the temperature was raised to 200[degrees]C. At 200[degrees]C, PCBs were effectively extracted at any pressure (150--650 atm), while both higher temperature and pressure increased the recovery of PAHs from air particulates. These results demonstrate that temperature is more important than pressure for achieving high extraction efficiencies when the interactions between pollutant molecules and sample matrices are strong and indicate that increasing SFE temperatures may be a useful alternative to adding organic modifiers for achieving high extraction efficiencies from environmental samples. 32 refs., 4 figs., 3 tabs.