CCQM-K43 was organized as a follow-up key comparison to the previous pilot study on tuna fish. CCQM-K43 was an activity of the Inorganic Analysis Working Group (IAWG) of CCQM and was coordinated by the Joint Research Centre–Institute for Reference Materials and Measurements (IRMM, Geel, Belgium) of the European Commission (EC). In CCQM-K43 the amount contents of As, Hg, Pb, Se and methylmercury (CH₃Hg) in salmon (muscle and skin) were the measurands under investigation. Results were reported by 12 national metrology institutes (NMIs). During the CCQM–IAWG autumn meeting in Berlin, October 2005, it was agreed that in CCQM-K43 the KCRV is calculated as the mixture model median (MM-median) of all reported results.

The reported results of the NMIs fall within a range of ±5% for arsenic and of ±2% for lead and mercury relative to the KCRV. For selenium the spread of all laboratories but one is ±8%. Also, for methlymercury four of the five participating NMIs reported results within 4% deviation from the KCRV.

The methods applied were isotope dilution mass spectrometry (IDMS) using sector field or quadrupole inductively coupled plasma-mass spectrometry (ICP-MS) or thermal ionization mass spectrometry (TIMS), external calibration using ICP-MS or atomic absorption spectrometry (AAS). Instrumental neutron activation analysis (INAA) and k₀-neutron activation analysis (k₀-NAA) were also used as analytical techniques.

This report presents the participants' results in CCQM-K43 for all analytes under investigation. In Annex 1, the results with the KCRV, the equivalence statements and the results sorted according to analytical technique applied are presented. In Annex 2, the different approaches for methlymercury measurements are presented in more detail. In Annex 3, the questionnaire data are presented. Annex 4 compiles all the CCQM-K43 information documents.

The pilot study CCQM-P39.1 was carried out in parallel to this key comparison for the same measurands in the same salmon material. Participation was meant for IAWG members, who did not immediately want to report results in a key comparison, and invited expert laboratories.

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The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).