Supercritical fluid extraction, microwave assisted extraction and soxhlet extraction for the analysis of PCB's in soil and sewage sludge

The supercritical fluid extraction (SFE) was applied on the analysis of PCB's in soil and sewage sludge. Some questions concerning the performance of SFE were studied. With spiked samples and the modifier toluene put directly onto the sample the effect of a static extraction before the dynamic extraction step is described. It was found that matrices with a high content of total organic carbon show matrix effects in SFE, which was identified by calibration of the whole analytical process and eliminated by repeating the extraction. Two real samples were used to compare the SFE with soxhlet extraction and organic solvent extraction by means of microwave energy. The extracts were cleaned by column chromatography on aluminium oxide and silica gel modified with silver nitrate and afterwards analysed by GC-ECD and GC-MS (SIM mode). Soxhlet and SFE gave comparable results. The best extraction results were achieved by microwave assisted extraction with a solvent mixture of hexane/acetone 3:1.