SUPERCRITICAL-FLUID EXTRACTION OF POLYCYCLIC AROMATIC-HYDROCARBONS FROM A MARINE SEDIMENT AND ANALYTE COLLECTION VIA LIQUID-SOLID TRAPPING

A standard reference marine sediment (SRM HS-3) certified for polycyclic aromatic hydrocarbons (PAHs) was extracted with pure and toluene-modified supercritical carbon dioxide at various temperatures while the pressure was maintained at 400 atm (1 atm = 101325 Pa). The best results were achieved with toluene-modified carbon dioxide at 140 degrees C. Similar results were obtained when carbon dioxide was replaced with nitrous oxide. Analyte collection after off-line supercritical fluid extraction (SFE) was carried out with liquid-solid traps whereby analyte losses due to aerosol formation during the depressurization of the supercritical fluid were reduced. As the liquid-solid traps were developed from conventional clean-up systems, further clean-up steps became unnecessary in this study. Such traps yielded better PAH recoveries than SFE with analyte trapping in pure organic solvents. The results of the optimized procedure were compared with the certified PAH values, dth the results obtained by Soxhlet extraction with toluene and n-hexane-acetone and with published SFE results. With SFE instead of conventional Soxhlet extraction, the complete time required for the extraction, evaporation and clean-up steps can be reduced from ca. 27 h to ca. 3 h per sample.