OPTIMIZATION OF THE PARAMETERS IN SUPERCRITICAL-FLUID EXTRACTION OF POLYNUCLEAR AROMATIC-HYDROCARBONS FROM SOIL SAMPLES

Supercritical fluid extraction (SFE) was investigated as a sample cleanup and concentration method for the determination of polynuclear aromatic hydrocarbons (PAHs) in soil samples by HPLC. At first, spiked samples were used to optimize the extraction parameters. Recoveries between 88% for anthracene and 101% for benzo(a)pyrene were obtained for all 15 components investigated at pressures of 40 MPa and temperatures of 80 degrees C. The collection solvent of choice was 15 mL of acetone, which was also compatible with doe subsequent HPLC analysis. Methanol contents of 5% (mol) or 10% (mol) toluene as cosolvents was necessary to achieve equivalent extraction yields for SFE compared to Soxhlet extraction. The precision of the entire procedure including SFE and HPLC was around 10% RSD for all components, while HPLC contributed a 3.8% portion within the RSD. For real world soil samples, drying agents were used to trap the contained water of the soil sample and elemental copper granules were used to trap organosulfur compounds. Similar extraction yields were achieved for real world samples when the methanol content in carbon dioxide was increased to 8% (mol).