engleski

Uncertainties of measurements of polychlorinated biphenyls (PCBs) in biological samples

PCBs, a group of 209 congeners, are widely distributed in the environment. Of various analytical methods developed for their quantification, the most common are gas chromatography (GC) with electron capture detection and gas chromatography-mass spectrometry (GC/MS). In the past, PCBs were determined on packed GC columns and total PCB levels were determined by summing several peaks and comparing them to the sum of the corresponding peaks in the solution of commercial PCB mixtures. Due to the differences in commercial mixtures and differences in chromatographic conditions, results obtained in different laboratories were not always comparable because different PCB peaks were evaluated. It was not possible to identify individual congeners because every peak represented more than one compound. A solution to these problems was the introduction of perchlorination, which enabled measurement of total PCBs expressed as decachlorobiphenyl. Toxicological research showed, however, that PCB congeners differ greatly in toxic potential and that the information on the distribution of individual congeners is essential. Therefore, the perchlorination method has been discarded. The introduction of capillary columns in gas chromatography made possible congener specific analyses. However, different laboratories analyse different congeners and a different number of congeners. The comparison of PCB levels in various biological matrices and the evaluation of for instance time trends, geographic differences, and differences between species is complicated and sometimes even impossible. The main problem is to express results correctly. The examples below foreground problems related to comparison of PCB levels in human serum and milk. The levels of total PCBs (as compared to Aroclor 1260) were found to exceed the sum of six most often analyzed PCB congeners and to vary with matrix.

PCBs; biological samples; gas chromatography

nije evidentirano