On-line flash thermodesorption-GC-MS determination of PCB in sewage sludge

A flash thermodesorption-gas chromatography-mass spectrometry technique has been developed for the determination of polychlorobiphenyls (PCB), especially the highly toxic planar species, in sewage sludge. A modified Curie-point pyrolyzer was used; in this the flash-desorption temperature was controlled by selecting specific metal alloys for the pyrolysis wire. Samples (3 mg) were loaded into a quartz tube with the special heating wire wound around the outer wall. By this means rapid thermal desorption (TDS) was achieved whereas uncontrolled catalytic breakdown of the analytes was avoided. The thermodesorption unit was connected via a custom-built interface to the GC-MS detection system. The average limit of detection was 15 ng kg^-1 sludge more than one order of magnitude better than the legal requirement.