The determination of polychlorinated biphenyls in municipal sewage sludges using microwave-assisted extraction and gas chromatography-mass spectrometry

A fast GC-MS method for the determination of PCB in municipal sewage sludges was developed. Dried sewage sludge samples were prepared by microwave-assisted extraction (for 10 minutes at 30 Watts) with 30 ml hexane-acetone (1:1), followed by purification on disposable solid-phase extraction silica cartridges. Extractions were carried out in the presence of copper to prevent interference from sulphur. The samples were then analysed by GC on an HT-8 silica capillary open-tubular column with MS detection in the selected ion monitoring mode. The procedure was applied to sewage sludges from 2 municipal wastewater stations near Paris, Acheres and Valenton. Overall extraction recoveries ranged from 88 to 105 per cent. Acheres sludge PCB concentrations determined using microwave-assisted extraction were in reasonable agreement with those measured using the classical Soxhlet extraction method. To validate the method, results for several Valenton samples were compared with those obtained by an independent laboratory using Soxhlet extraction, clean-up on Florasil, and GC with electron-capture detection. The results compared favourably, although some differences were observed.