Pressurized hot water extraction (PHWE) ofn-alkanes and polyaromatic hydrocarbons (PAHs): Comparison for PAHs with supercritical fluid extraction

High-temperature liquid water and steam were used to extract n alkanes and polyaromatic hydrocarbons (PAHs) from spiked sea sand at different temperatures. Pressurized hot water extraction (PHWE) was followed by solid phase collection. Tenax as the trapping material with n-heptane as the eluent gave recoveries larger than 95% for diesel hydrocarbons extracted with steam at 250°C. Recoveries from Tenax of hydrocarbons extracted with liquid water under the same conditions were lower. Good (>90%) recoveries were also obtained for low molecular weight PAHs, extracted with steam at 250°C and with n-heptane as eluent for the Tenax trap. n-Heptane containing 10% ethyl acetate was more efficient, eluting high as well as low molecular weight PAHs with good recovery. PHWE was also tested in the extraction of a real sediment sample certified for PAHs, and the results were compared with those obtained with supercritical fluid extraction (SFE) using neat CO2 and modified CO2. Steam at 250°C and 300°C gave similar recoveries as those obtained by SFE with use of a modifier.