CCQM-P39: As, Hg, Pb, Se and methylmercury in tuna fish

CCQM-P39 was an activity of the Inorganic Analysis Working Group (IAWG) of CCQM and was organised by the Institute for Reference Materials and Measurements (IRMM, Geel, Belgium) of the European Commission (EC). In CCQM-P39 the amount contents of As, Hg, Pb, Se and methylmercury (CH3Hg) in tuna fish muscle were the measurands under investigation. Besides the National Metrology Institutes (NMIs) who are IAWG members, non-IAWG members, expert laboratories for mercury and methylmercury measurements, were also invited to participate in this pilot study. Finally, results were reported by 13 NMIs and 8 expert laboratories. The results of the IAWG members for arsenic and selenium fall within a range of 10% with respect to the mixture model median (MM-median). For lead, the spread was within 2% and for mercury within 4% deviation from the MM-median. Also, for methlymercury the majority of the participating NMIs reported results within 4% deviation from the MM median. Including the reported results from the invited expert laboratories, the spread of results increased for arsenic, lead, selenium and methlymercury up to 20%-40%. Except for mercury, for this analyte the spread of all the reported results of the IAWG members and the invited expert laboratories was within 4%. The methods applied were isotope dilution mass spectrometry (IDMS) using sector field or quadrupole inductively coupled plasma mass spectrometry (ICP-MS), external calibration using time-of-flight MS, atomic absorption spectrometry (AAS) or atomic fluorescence spectrometry (AFS). Instrumental neutron activation analysis (INAA) and k(0)-neutron activation analysis (k(0)-NAA) were also used as analytical techniques. Each of the five analytes under investigation was measured with at least three of these analytical techniques. IAEA reported two results for arsenic, lead and selenium. They were measured with ICP-MS and AAS, respectively. This report presents the participants' results in CCQM-P39 for all analytes under investigation. In Annex 1, the results with the MM-median are presented and sorted according to analytical technique applied. In Annex 2, the different approaches for methlymercury measurements are discussed in more detail. In Annex 3, the questionnaire data are presented. Annex 4 compiles all the CCQM-P39 information documents. At the CCQM meeting in April 2004, it was decided to proceed this study to a key comparison and a pilot study for the same analytes in a salmon material, CCQM-K43 and CCQM-P39.1.