Role of Modifiers for Analytical-Scale Supercritical Fluid Extraction of Environmental Samples

Supercritical fluid extraction (SFE) using eight different CO[sub 2] + organic modifier mixtures and one ternary mixture (CO[sub 2] + methanol/toluene) at two different concentrations (1 and 10% v/v) was performed on two certified reference materials including polychlorinated biphenyls (PCBs) from river sediment and polycyclic aromatic hydrocarbons (PAHs) from urban air particulate matter. The modifier identity was more important than modifier concentration for increasing extraction efficiencies. Acidic/basic modifiers including methanol, acetic acid, and aniline greatly enhanced the extraction of PCBs. Low molecular weight PAHs were best extracted with modifiers including aniline, acetic acid, acetonitrile, methanol/toluene, hexane, and diethylamine. In contrast, modifiers capable of dipole-induced dipole interactions and [pi]-[pi] interactions such as toluene, diethylamine, and methylene chloride were the best modifiers to use for SFE of high molecular weight PAHs from air particulates. 37 refs., 6 tabs.