The aim of this comparison was to demonstrate the capability of national metrology institutes to measure elemental mass fractions at a level of w(E) ≈ 1 g/kg as found in almost all mono-elemental calibration solutions. These calibration solutions represent an important link in traceability systems in inorganic analysis. Virtually all traceable routine measurements are linked to the SI through these calibration solutions. Every participant was provided with three solutions of each of the three selected elements chromium, cobalt and lead. This comparison was a joint activity of the Inorganic Analysis Working Group (IAWG) and the Electrochemical Analysis Working Group (EAWG) of the CCQM and was piloted by the Physikalisch-Technische Bundesanstalt (PTB, Braunschweig, Germany) with the help of the Bundesanstalt für Materialforschung und -prüfung (BAM, Berlin, Germany), the Centro Nacional de Metrología (CENAM, Querétaro, Mexico) and the National Institute of Standards and Technology (NIST, Gaithersburg, USA).A small majority of participants applied inductively coupled plasma optical emission spectrometry (ICP OES) in combination with a variety of calibration strategies (one-point-calibration, bracketing, calibration curve, each with and without an internal standard). But also IDMS techniques were carried out on quadrupole, high resolution and multicollector ICP-MS machines as well as a TIMS machine. Several participants applied titrimetry. FAAS as well as ICP-MS combined with non-IDMS calibration strategies were used by at least one participant. The key comparison reference values (KCRV) were agreed upon during the IAWG/EAWG meeting in November 2011 held in Sydney as the added element content calculated from the gravimetric sample preparation. Accordingly the degrees of equivalence were calculated. Despite the large variety of methods applied no superior method could be identified. The relative deviation of the median of the participants' results from the gravimetric reference value was equal or smaller than 0.1% (with an average of 0.05%) in the case of all three elements.Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).
The subsequent key comparison CCQM-K19.1 was carried out in 2010 as a follow-up comparison to CCQM-K19. Three laboratories (NMIJ, PTB and SMU) took part in both comparisons. Their results are consistent. The assigned uncertainties are reliable and of the same order. These results provide the link to CCQM-K19.As well as the original comparison the subsequent key comparison was organized to demonstrate the capability of the interested national metrology institutes to measure the pH value of an unknown borate buffer by a primary method at 15 °C, 25 °C and 37 °C. Eight laboratories took part in CCQM-K19.1. The participants either were not able to participate in the original comparison or participate only in the Pilot Study CCQM-P82 running in parallel to CCQM-K19. In one case the laboratory expressed doubts on the integrity of the sample provided in CCQM-K19.The result in CCQM-K19.1 is the acidity function at zero chloride molality of the unknown borate buffer solution.Most participants in the key comparison CCQM-K19.1 demonstrated improved capabilities. This especially applies to the laboratories that had originally taken part in the pilot study CCQM-P82. In some cases previous results could be confirmed. The hidden reasons for that have still to be clarified.Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).
The subsequent key comparison CCQM-K18.1 was started in order to evaluate the equivalence of metrology institutes as a follow-up to the previous key comparison CCQM-K18 for institutes that could not take part in the comparison at that time or did not consider their results representative of their capabilities. A carbonate buffer of a slightly different composition to that in CCQM-K18 was used.There were seven institutes plus the coordinating laboratory participating in this subsequent comparison. Most of the participating institutes showed significant improvement; in some cases the new results confirmed the previous ones. The reasons for this have still to be elucidated. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).
The key comparison CCQM-K18 was started in order to evaluate the equivalence of metrology institutes as a follow-up of the previous study CCQM-P52. As a sample a carbonate buffer solution was used with a composition slightly different to the usual one. There were 13 institutes participating in the comparison using a primary method for pH measurement. The fair agreement between the results reflects increased difficulty in measurement, where the buffer composition may slightly change during the measurement and extrapolation to the start time of measurement is usually necessary.Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).
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