SUPERCRITICAL CARBON-DIOXIDE EXTRACTION OF POLYCYCLIC AROMATIC-HYDROCARBONS FROM SEDIMENTS

A supercritical fluid extraction (SFE) method using carbon dioxide was developed for the determination of the 16 US Environmental Protection Agency polycyclic aromatic hydrocarbon (PAH) priority pollutants in naturally contaminated sediments. While carbon dioxide is less efficient for the heavier PAHs than other fluids such as nitrous oxide and Freon-22, its deficiency was remedied by the use of a mixture of water, methanol, and dichloromethane as modifiers, a higher extraction temperature of 120 degrees C, as well as repetitive extractions. Extraction time can be further reduced to ca. 70 min per sample if a high-pressure pump is used for the delivery of the modifiers during dynamic extraction. Except for naphthalene, the SFE results for the 16 PAHs obtained from several certified reference materials and sediments samples were comparable to certified or Soxhlet values in terms of both precision and accuracy. The SFE recoveries of naphthalene as well as methylnaphthalenes which were coextracted alongside other PAHs and methyl-PAHs, ranged from 150 to 125% of their respective Soxhlet values due to higher evaporative losses in the Soxhlet procedure.