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

Supercritical fluid extraction (SFE) was investigated as a sample clea nup and concentration method for the determination of polynuclear arom atic hydrocarbons (PAHs) in soil samples by HPLC. At first, spiked sam ples were used to optimize the extraction parameters. Recoveries betwe en 88% for anthracene and 101% for benzo(a)pyrene were obtained for al l 15 components investigated at pressures of 40 MPa and temperatures o f 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 e xtraction. The precision of the entire procedure including SFE and HPL C was around 10% RSD for all components, while HPLC contributed a 3.8% portion within the RSD. For real world soil samples, drying agents we re used to trap the contained water of the soil sample and elemental c opper granules were used to trap organosulfur compounds. Similar extra ction yields were achieved for real world samples when the methanol co ntent in carbon dioxide was increased to 8% (mol).