Intercomparison study on milk powder fortified with PCDD and PCDF

Summary

In order to find out the state of the art of dioxin analyses in cow's milk the BCR has organised an intercomparison in native and fortified milk-powders. The preparation of the milk-powder batches is described. Laboratories (n=11) have used their own in-house methods and standards. The use of a high resolution MS (R=10 000) was requested. An outline is given of how the results obtained were interpreted in discussions with the participants. A major problem in the quantification is the lack of certified standard solutions of all seventeen 2,3,7,8 congeners, this was shown during the analysis of the BCR standard solution. Recovery of the fortified dioxins from the milk-powders were in general between 80–90% of the added values. A further problem was the analysis of hepta and octa chlorinated congeners; for the calculation of international toxicological equivalent quantities (I-TEQ), larger variations in these did not significantly affect the total I-TEQ in milk-powder. Most of the participants were able to deliver satisfactory results for judging the acceptability of the milk for human consumption.