EXTRACTION OF A QUALITY ASSURANCE SEDIMENT SAMPLE FOR POLYCHLORINATEDDIBENZO-P-DIOXINS AND DIBENZOFURANS (PCDD F)/

An experimental design for two variables at three and four levels was used to investigate the Soxhlet extraction of polychlorinated dibenzo- p-dioxins/dibenzo-furans (PCDD/F) from a quality assurance sediment. T he first variable was the solvent: toluene/methanol, toluene (both Sox hlet) and toluene in Soxhlet-Dean-Stark equipment. The second variable were four different bulks: silica, sulfuric acid treated silica, sodi um carbonate and no bulk. Extractions with toluene/methanol and sulfur ic acid provided only a small contribution to the overall extraction e fficiency. Toluene/methanol preferably improved the extraction of PCDD , and the sulfuric acid improved the PCDF extraction. This was likely to reflect improved extraction efficiency of substructures in the sedi ment as pulp effluent remains (fiber) and fly-ash particulate. A previ ously found PCDD formation in extractions using toluene/methanol in pr esence of sodium carbonate was reproduced. A designed supercritical fl uid extraction (SFE) experiment was also accomplished, however even un der the best used conditions some PCDD/F were retained on the particul ate compared to Soxhlet extraction. Variations in extraction efficienc y in Soxhlet and SFE indicated that different subfractions of PCDD/F a re connected to the matrix with different mechanisms, thus indicating that different PCDD/F fractions had different abilities to equilibrate also in the real environment.