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), especia lly the highly toxic planar species, in sewage sludge. A modified Curie-poi nt pyrolyzer was used; in this the flash-desorption temperature was control led by selecting specific metal alloys for the pyrolysis wire. Samples (3 m g) were loaded into a quartz tube with the special heating wire wound aroun d 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 mug kg(-1) sludg e-more than one order of magnitude better than the legal requirement.