ABSTRACT
Polychlorinated biphenyls (PCBs) are a class of chlorosubstituted biphenyl compounds that were once widely used as additives in transformer oils, lubricating oils, and hydraulic uids. ese substances have high boiling points, and exhibit high chemical and thermal stability, and ame resistance. However, because of their high toxicity and possible carcinogenic action in humans, these substances are no longer being used. In the United States, PCBs were made under the trade name Aroclor. Table 47.1 presents the common Aroclors, their CAS numbers, and the chlorine contents. Each Aroclor is a mixture of several isomers. e general structure of the biphenyl ring is as follows:
PCBs can be conveniently determined by most of the common analytical techniques that include GC-ECD, GC-HECD, GC-FID, GC/MS, HPLC, NMR, and enzyme immunoassay. Among these, GC-ECD and GC/MS are by far the most widely used techniques for the determination of PCBs in the environmental samples at a very low level of detection. While the former can detect the PCBs at subnanogram range, the mass selective detector (GC/MS) identi es the components relatively at a higher detection range, 10-50 times higher than the ECD detection level. GC/ MS, however, is the best con rmatory method to positively con rm the presence of PCBs, especially in heavily contaminated samples. Aqueous and nonaqueous samples must be extracted into a suitable solvent prior to their analysis.
