Design for on-line coupling of supercritical fluid extraction with liquid chromatography: quantitative analysis of polynuclear aromatic hydrocarbons in a solid matrix

Supercritical fluid extraction (SFE) was directly coupled with high-performance liquid chromatography (LC) via the simplest interface--only one six-port injection valve. By using water to eliminate decompressed CO2 gas in the solid-phase octadecylsilica trap, high extraction recovery (> or = 95%) of polynuclear aromatic hydrocarbons (PAHs) from a sand matrix was achieved under optimized conditions. The volume of rinse water had little influence on the recovery, due to the very low solubility of PAHs in water and the sorption properties of the C-18 trap. Different amounts of sand matrix with a fixed mass of analytes have also been tested. No decrease in recovery was found when the matrix (sand) increased from 1 to 10 g. Methanol and acetone were used as a CO2 modifier to enhance the extraction efficiency. Finally, PAHs in naturally contaminated soil were successfully extracted and quantitatively determined by this hyphenated system. Compared to the EPA method (Soxhlet extraction following by GC/MS), on-line SFE-LC gave precise results in a much shorter time.