Ion analysis at the highest stage: The Metrological approach by National Metrological Institutes

National Metrological Institutes (NMI's) from fifteen different countries participated in interlaboratory comparisons where concentrations of about 1 gkg-1 in solutions of aluminium, copper, iron, magnesium, chloride and phosphate were measured. A very high comparability of the results irrespective of the analyte and the applied measurement technique was observed. The relative in-between laboratory standard deviations of the results as reported by the participating laboratories were between 0.13% for copper and chloride up to 0.33% for aluminium, and all of the 81 results were found in the range of -l % with respect to the reference value. Due to the gravimetric preparation of the samples, a conventional true reference value was calculated, and no significant deviations of the reference values and the means of all results reported by the institutes were found.