2009_Book_FoodChemistry

9.6 Polychlorinated Biphenyls (PCBs) 489
Fig. 9.3. (Continued)
The analysis starts with screening. Antibiotics
can be detected with the help of the
bacteria whose growth they inhibit. Their
differentiation can be further improved by
means of an electrophoretic preliminary separation.
In principle, the same isolation and separation
methods and mass spectrometric techniques are
used for the unambiguous identification of veterinary
medicines as for pesticides (cf. 9.4.3). Enzyme
immunoassays are also used (cf. 2.6.3).
9.6 Polychlorinated Biphenyls
(PCBs)
The PCBs are complex mixtures of substances
which have been on the market since 1950.
They are widely used, e. g., as transformer
oil, hydraulic fluid, heat exchange medium,
dielectric fluid in condensers, plasticizer and
additive for printing ink. Formula 9.3 shows
2,2 ′ ,5,5 ′ -tetrachlorobiphenyl (I) and 2,2 ′ ,4,5,5 ′ -
pentachlorobiphenyl (II) as examples.