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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.
A pilot study for the quantitative surface analysis of multi-element alloy films has been performed by the Surface Analysis Working Group (SAWG) of the Consultative Committee for Amount of Substance (CCQM). The aim of this pilot study is to ensure the equivalency in the measurement capability of national metrology institutes for the quantification of multi-element alloy films. A Cu(In,Ga)Se2 (CIGS) film with non-uniform depth distribution was chosen as a representative multi-element alloy film. The atomic fractions of the reference and the test CIGS films were certified by isotope dilution - inductively coupled plasma/mass spectrometry. A total number counting (TNC) method was used as a method to determine the signal intensities of the constituent elements, which are compared with their certified atomic fractions. The atomic fractions of the CIGS films were measured by various methods, such as Secondary Ion Mass Spectrometry (SIMS), Auger Electron Spectroscopy (AES), X-ray Photoelectron Spectroscopy (XPS), X-Ray Fluorescence (XRF) analysis and Electron Probe Micro Analysis (EPMA) with Energy Dispersive X-ray Spectrometry (EDX). Fifteen laboratories from eight National Metrology Institutes (NMIs), one Designated Institute (DI) and six non-NMIs participated in this pilot study. Although the average atomic fractions of 18 data sets showed rather poor relative standard deviations of about 5.5 % to 6.8 %, they were greatly improved to about 1.5 % to 2.2 % by excluding 5 strongly deviating data sets from the average atomic fractions. In this pilot study, the average expanded uncertainties of SIMS, XPS, AES, XRF and EPMA were 3.84%, 3.68%, 3.81%, 2.88% and 2.90%, respectively. These values are much better than those in the key comparison K-67 for composition of a Fe-Ni alloy film. As a result, the quantification of CIGS films using the TNC method was found to be a good candidate as a subject for a CCQM key comparison.
CCQM (Consultative Committee for Amount of Substance - Metrology in Chemistry) is an international body of the Meter Convention (BIPM) established as a framework of National Metrology Institutes running inter-laboratory of comparisons to demonstrate the international comparability of chemical measurements, with traceability to international or national reference standards. In 2003 the surface analysis working group (SAWG) was established at CCQM and since then several inter-laboratory comparisons in the field of EPMA have been carried out. In many cases the EPMA results deviated significantly from each other and the expanded uncertainties were greater than expected. Both methods EDS and WDS were employed. However, light elements such as carbon and nitrogen were the major elements analyzed and it is known that the corresponding lowenergy characteristic X-ray lines are more challenging to quantify by EPMA than the higher energy lines of elements with higher atomic numbers. Moreover, the standards selected and their qualities were variable, the quantification models were different, and the acquisition parameters were not specified sufficiently in the analysis instructions.