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Subject - Organic Chemistry, Toxicology
PCB is an abbreviation for polychlorinated biphenyls, a group of 209 congeneric compounds which differ in number and position of chloro substituents in the biphenyl system. Technically, PCBs are mixtures with tradenames such as Aroclor (USA), Clophen (Germany), Sovol (former USSR), etc. which differ in the degree of chlorination (30-60%) and, therefore, in their physical properties. The classification of PCB congeners, called the Ballschmiter number, internationally follows the system developed by the German environmental chemist Karlheinz Ballschmiter.
Because of their high thermal and chemical stability as well as their very low electrical conductivity and non-flammability, PCBs were originally used as coolants and insulating liquids in high-voltage transformers and capacitors as well as in hydraulic systems and even as softeners. Because of high lipophilicity and very high stability towards chemical or biological degradation, PCBs are ubiqitous and accumulate in the food chain (breast milk). Though the use of PCBs has been strictly regulated over the last 20-30 years in most industrial countries (USA 1979), they still are stubborn environmental contaminants. Together with dioxins which they resemble in their environmental behavior and for which they could be possible precursors, PCBs belong to the most intensively investigated materials. Usually, GC/ECD or GC/MS are used for their detection.