Limitations in the Use of Perchlorination as a Technique for the Quantitative Analysis of Polychlorinated Biphenyls

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Abstract
Quantitative analysis of mixtures of polychlorinated biphenyls (PCBs) is frequently done by means of perchlorination of all individual PCBs to decachlorobiphenyl, with subsequent determination on a gas chromatograph equipped with an electron-capture detector. The potential of this perchlorination technique has been evaluated by comparing results so obtained with those of the conventional pattern-comparison method, using both non-biological and biological samples. With the former type of sample (paper, paper board, printing inks, sewage sludge) the PCB content as calculated from perchlorination data almost invariably is much higher—typically 2-30-fold—than that calculated on the basis of the pattern-comparison technique. With biological samples, large discrepancies also occur but much less frequently. In an attempt to interpret these findings, the behaviour—under perchlorination conditions—of related types of compounds, such as polychlorinated terphenyls and naphthalenes, polybrominated biphenyls, hydroxylated biphenyls and organochlorine pesticides, has been studied. Evidence is presented to show that the presence of these types of compounds generally cannot explain the high results obtained for PCBs after perchlorination. With some recycled paper samples, high-performance liquid chromatographic (HPLC) fractionation and subsequent gas chromatography-mass spectrometry has allowed the isolation and identification of several hydrogenated terphenyls, which appear to be the main interfering compounds. This has been confirmed during a study of the commercial hydrogenated terphenyl-containing product HB-40. Dechlorination of PCB mixtures and HPLC analysis, with UV detection, of the biphenyl formed is discussed as a promising alternative to perchlorination.