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The key comparison CCQM-K33 was organized by the Inorganic Analysis Working Group of the CCQM to test the abilities of the national metrology institutes to measure the mass fractions of minor elements in steel. Elements to be analysed were Cr, Mn, Ni and Mo in low alloy steel. The National Metrology Institute of Japan (NMIJ), the National Institute of Standards and Technology (NIST) and the Federal Institute for Materials Research and Testing (BAM) acted as the coordinating laboratories. The participants used various measurement methods, though many of them used ICP-AES. Generally speaking, the agreement of the results was very good for each measurand.
The capabilities of National Metrology Institutes (NMIs) and selected outside expert laboratories of determining the mass fractions of the main and minor elements Cu, Pb, Sn, Fe, and Ni in a lead-containing brass were assessed. This pilot study P76 was organized as an activity of the Inorganic Analysis Working Group of CCQM and was piloted by the Federal Institute for Materials Research and Testing (BAM). In total 12 laboratories (four NMIs and eight outside labs) submitted results, some of them more than one set of results per element. The laboratories were free to choose any analytical method they wanted to use for the analysis. Consequently various methods of measurement were employed: inductively coupled plasma optical emission spectrometry (ICPOES), inductively coupled plasma mass spectrometry (ICPMS), instrumental neutron-activation analysis (INAA), titrimetry, flame atomic-absorption spectrometry (FAAS), spectrophotometry (MAS), electrogravimetry, and gravimetric analysis. After testing for homogeneity within BAM, a certified reference material of lead-containing brass was used as test sample without informing the participants about the source of the material. The agreement of the results for all elements investigated was acceptable and mean values calculated from the results of all participants were close to the certified mass fractions of the CRM used as test sample. No statistically significant differences between the results of the NMIs and those of the non-NMIs could be observed.
Three methods for direct solid sampling of bulk material namely IR laser ablation, glow discharge and spark OES, were compared with respect to analytical figures of merit obtained for elemental analysis with atomic spectrometry. Matrices investigated were copper, pressed doped copper powder, and magnesium alloys. For the vast majority of analytes, statistical equivalence regarding precision (usually ≤ 5%) and the performance of the calibrations between the compared methods was demonstrated.
The degree of equivalence within the participating national metrology institutes for the measurement results of the mass fractions of the analytes Cr, Cu, Fe, Mn and Zn in an aluminium alloy was assessed. This interlaboratory comité consultatif pour la quantité de matière key comparison (CCQM-K42) was organised as an activity of the Inorganic Analytical Working Group of CCQM. In total seven laboratories participated, six of them for all analytes. Measurands were the mass fractions of the analytes in a range of 0.05 and 0.2%. As an outcome the consistency of the results for all elements investigated was acceptable, hence satisfactory comparability was established. An aluminium based certified reference material—undisclosed to the analysts which one it was—was used as test sample. For the purpose of this study homogeneity was tested at BAM. Each laboratory was free to choose any analytical method they wanted to use for the analysis. Consequently various methods of measurement were employed: instrumental neutron activation analysis, X-ray fluorescence spectrometry (XRF) using fused cast-bead method combined with reconstitution technique, inductively coupled plasma optical emission spectrometry (ICP OES) and inductively coupled plasma mass spectrometry. Metrological traceability of the measurement results to the SI unit had to be demonstrated. Therefore, methods such as spark OES or XRF (without fused cast-bead technique)—both of them being most important methods for the analysis of metals and alloys in industrial laboratories—could not be used in the frame of the key comparison.
The special importance of the analysis of non-metals in high purity metals, which will serve as national standards for elemental analysis in Germany, is illustrated for oxygen and nitrogen. The typical range of the mass fraction of oxygen and nitrogen in these materials is below 10.MU.g/g, often close to 1.MU.g/g. The two methods applied at BAM for these measurements are classical carrier gas hot extraction (HE) and carrier gas hot extraction after activation with photons (PAA-HE). The approach, the methods and their advantages and limitations are discussed. Comparative results from the measurement of oxygen and nitrogen in Cu, Fe, Ga, Pb, Sn and W are presented. (author abst.)