ON THE SUITABILITY OF 2,3,4,7,8-PECDF AS PILOT CONGENER OF THE DIOXINFURAN CONTENT IN RAW-MILK

To be able to define a compound as typical pilot congener from a conge ner mixture, as represented by the theoretically possible 21 0 polychl orinated dibenzodioxins and -furans and the 17 laterally substituted c ongeners, the compound coming into consideration has to fulfill essent ial-criteria, e.g. the prominent occurrence in emissions and depositio ns/immissions, transfer factors within the food chain furnishing proof of an enrichment with substrate change, high carry-over rates conside ring foodstuffs originating from animals, further, special analytical advantages e.g. sensible response of the detection system and a measur ing technique at reasonable cost. The 2,3,4,7,8-PeCDF seems to fulfil these requirements to a far extent, because it represents roughly half of the toxic PCDD/F equivalents in milk fat, shows a carry-over rate from feedingstuff into milk fat of 25 - 30%, is very highly correlated with the other congeners of the mixture in the matrix and can be dete cted with high sensitivity and mass selectively by means of chemical i onization with negative ion registration in simple GC/MS combinations. On the other hand, extensive and, to a far extent, coextractive-free sample preparation is indispensable, so that here almost no advantages are to be expected compared with the classical high resolution mass s pectrometry. The main argument for restricting the dioxin-/furan measu rement in milk fat to the pilot congener is its rather close correlati on to the other dioxins and furans studied (up to r=0.99) with actuall y comparable samples. In addition, the expenditure for the final deter mination is considerably lower from the point of view of technique and cost, so that at least screening'' for detecting the background conta mination of PCDD/F in milk fat could be an area of application for thi s method.