Comparison of low-level polycyclic aromatic hydrocarbons in sediment revealed by Soxhlet extraction, microwave-assisted extraction, and pressurized liquid extraction.

We analyzed polycyclic aromatic hydrocarbons (PAHs) present in lake sediment at low levels (<1 microg g(-1)) by using Soxhlet extraction (Soxhlet), microwave-assisted extraction (MAE), and pressurized liquid extraction (PLE) in combination with gas chromatography and isotope-dilution mass spectrometry. Although all extraction techniques showed good repeatability for five target PAHs (relative standard deviation <5.2%, n=3), the results decreased in the order PLE>MAE>Soxhlet. Differences in the results originated mainly from differences in the extraction efficiencies of the techniques for native PAHs, because all techniques gave comparable recovery yields of corresponding 13C-labeled PAHs (13C-PAHs) (51-84%). Since non-negligible amounts of both native PAHs and 13C-PAHs were re-adsorbed on matrix in MAE, not only recovery yields of 13C-PAHs but also efficiencies of extraction of native PAHs should be examined to evaluate the appropriateness of any analytical procedures.