Evaluation of supercritical fluid extraction for isotope dilution gas chromatography-mass spectrometric quantification of polychlorinated biphenyls in sediment

Supercritical fluid extraction (SFE) has been evaluated as an extraction technique for the isotope-dilution quantification of polychlorinated biphenyls (PCBs) in a sediment sample. A high-resolution mass-spectrometric system equipped with a gas chromatograph was employed for the determination of seven target PCB congeners. The effect of the operation parameters on the SFE efficiency was investigated, in which the analytical values of five target PCB congeners significantly increased with increases in the extraction temperature and pressure, and that of 4,4'-dichlorobiphenyl further increased by applying static extraction. The following conditions were found to be optimal: extraction temperature, 140 degrees C; pressure, 30 MPa; time and mode, static for 15 min then dynamic for 30 min. Under these conditions, the addition of modifiers influenced the extraction of polar compounds, but did not affect the analytical values of the PCB congeners. The optimized method was suitable for high-throughput analysis as well as for providing accurate analytical results, which were comparable to or better than the analytical results obtained by Soxhlet extraction.