CONGENER-SPECIFIC METHOD FOR THE DETERMINATION OF ORTHO AND NON-ORTHOPOLYCHLORINATED-BIPHENYLS, POLYCHLORINATED DIBENZO-P-DIOXINS AND POLYCHLORINATED DIBENZOFURANS IN FOODS BY CARBON-COLUMN FRACTIONATION AND GAS-CHROMATOGRAPHY ISOTOPE-DILUTION MASS-SPECTROMETRY

The chromatographic behavior of oi tho and non-oi tho polychlorinated biphenyls (PCBs) on supported carbon columns has been investigated and the structure-affinity relationship of activated carbon towards PCB m olecules established. Optimisation of the parameters controlling the e lution of PCB congeners through the carbon column led to the developme nt of a solvent scheme for the efficient separation of (i) ortho subst ituted PCBs, (ii) non-oi tho substituted PCBs and (iii) polychlorinate d dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in three separate fractions. A method for the extraction? clean-up, fr actionation and determination of ortho and non-ortho substituted PCBs by GC-isotope dilution MS was developed and validated by analysis of a certified reference material. Possible losses of PCBs during freeze-d rying and interferences of aliphatic hydrocarbons during mass spectrom etric determination of ortho substituted PCBs are also discussed.