Interlaboratorium Vergelijkingsonderzoek voor de bepaling van Polychloordioxinen en Dibenzofuranen in melkpoeder. Resultaten van deelname aan een eerste Europees ringonderzoek door het Bureau Communautaire de Reference (BCR)

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This report summarizes the results of a first European interlaboratory calibration study by the Bureau of Reference (BCR) of the European Commission on the analysis of PCDD/Fs in milk powder by laboratories of the EC. In total nine laboratories from Belgium (1), Germany (3), England (1) and the Netherlands (4) and two laboratories from Sweden and Finland, respectively, have completed the study. Ten other laboratories, who initially agreed with participation, have not submitted their results. The study comprised of a comparison of the own standards of laboratories with a common standard of the BCR and the analysis of PCDD/Fs in an authentic and two spiked milk powders samples with levels between the background level and five times this level in cow's milk. The overall analytical results by all participant laboratories showed a considerable large variation, both in the quantified amounts in the common standard and the levels in three milk powder samples. Results of about one quarter of laboratories differed significantly the means, whereas the results of the remaining participants agreed well within acceptable limits (+- 25%). In general results of RIVM were close to the means. The within-laboratory reproducibility of RIVM was on average within 10%. The accuracy of the method based on agreement with assigned values, was better than 90% on average. Concentrations of native PCDD/Fs in standard mixture agreed on average within 15% to that in the BCR standards. A comparison on the basis of degree of experience of laboratories showed that, with a few exceptions, a long-standing experience and access to state-of-the art GC/HRMS instrumentation are obviously demanding conditions to be able to perform reliable analysis of PCDD/Fs at the sub parts-per-trillion level in cow's milk.