COMPARISON OF HIGH-RESOLUTION GAS-CHROMATOGRAPHY WITH ELECTRON-IMPACTAND NEGATIVE-ION MASS-SPECTROMETRY DETECTION FOR THE DETERMINATION OFCOPLANAR POLYCHLOROBIPHENYL CONGENERS IN SEWAGE SLUDGES

The three most toxic coplanar PCB 77, 126 and 169 have been identified and quantified at ultra trace levels (0.02 - 4.8 ng/g dw) in swiss se wage sludge samples applying high resolution capillary gas chromatogra phy (HRGC) and electron impact (EI) as well as negative ion chemical i onization (NCI) mass spectrometry (MS). NCI mass spectra have been dom inated by the molecular ion as base peak and virtually no fragmentatio n has been observed. Detection limits of the planar PCB under single i on monitoring (SIM) conditions have been typically 100 fg for NCI-MS a nd 1 pg for EI-MS. NCI-MS was the preferred detection method for the d etermination of very low concentrations of these important contaminant s in sewage sludge samples.