Certification of trace and major elements and methylmercury concentrationsin a macroalgae (Fucus sp.) reference material, IAEA-140

A marine reference material, IAEA-140, prepared with a macroalgae (Fucus sp .) was recently produced by the International Atomic Energy Agency and cert ified for trace and major elements and for methylmercury (MeHg). Certificat ion of this material was achieved as an outcome of an international analyti cal intercomparison study which resulted in 116 independent sets of results reported by participants from 54 countries, The statistical evaluation of the collected data and the criteria used for assignment of the mean and unc ertainty values are described. The analysis of data allowed to certify conc entration values for 24 elements and MeHg, and to provide information value s for another 10 elements, Regarding the elements which could be given cert ified values, between two and eight different instrumental methods were use d to measure metal concentrations, and four independent analytical procedur es were used to measure MeHg concentrations. In order to assess: the result s of the certification procedure. a comparison was made between the certifi ed values obtained from the world-wide intercomparison results and the valu es obtained from a small subgroup of well-qualified laboratories. The means and 95% confidence intervals for reference values obtained by the two meth ods are similar for most elements showing that the usual method of certific ation used by the IAEA, based on large groups of participants, is indeed pe rtinent.