COMBINED TEMPERATURE MODIFIER EFFECTS ON SUPERCRITICAL CO2 EXTRACTION EFFICIENCIES OF POLYCYCLIC AROMATIC-HYDROCARBONS FROM ENVIRONMENTAL-SAMPLES

Marine sediment, diesel soot, and air particulate matter were extracted with 400 atm of pure CO2 or modified CO2 (10 vol % methanol, diethylamine, or toluene added directly to the sample) at conventional (80 degrees C) and high (200 degrees C) temperatures for 15 min of static followed by 15 min of dynamic SFE. Pure CO2 extractions were also performed for 30 min in the dynamic mode and showed no significant increase in recoveries over pure CO2 extractions with the static/dynamic procedure. An increase in PAH recoveries was observed from all three samples by raising the temperature of either the pure or modified CO2 from 80 to 200 degrees C, which demonstrates that the temperature enhancement is independent of the sample matrix. In contrast, the modifier effects at both 80 and 200 degrees C were dependent on the sample matrix and modifier identity. In general, methanol was the poorest modifier for all three samples at either temperature and frequently yielded no increase in recoveries compared to pure CO2. Both toluene and diethylamine yielded increased recoveries at both temperatures from the air particulate matter, but only diethylamine gave significantly enhanced recoveries from all three samples. The enhancement in recoveries with high temperature and modifier were additive, indicating that temperature and modifiers have different mechanisms of improving PAH recoveries. Extractions at 200 degrees C with diethylamine modifier yielded the highest recoveries, which agreed well with recoveries determined by 14-48-h Soxhlet extractions.