Abstract. The aim of this comparison was to compare capabilities for the preparation and value assignment of gas mixture standards for sulphur dioxide in air (or nitrogen), maintained at national metrology institutes (NMIs). The measurements in this key comparison took place in 2006. There were three participants and one coordinating laboratory. The key comparison reference value (KCRV) was based on the gravimetric preparation for all components. The range of the nominal amount-of-substance fractions of the comparison standard is 90 µmol/mol to 100 µmol/mol. The Chemical Evaluation Research Institute (CERI, Japan) prepared gravimetric mixture samples of sulfur dioxide in nitrogen in 10 L aluminium cylinders with a passivated inner surface. The homogeneity and long term stability of these samples were evaluated at CERI before and after the shipment of the cylinders to the participants. The uncertainty of the standard gases including the long term stability was estimated to be 0.1 %. Each participating laboratory was shipped one cylinder to be analyzed and then returned to the CERI. Three participants submitted results that were within 0.6% of the relevant reference value. In these cases, the estimated uncertainties were larger than the deviation from the reference value. The agreement of the results in this key comparison is good. CERI is the link laboratory between CCQM-K1.d and APMP.QM-K4.

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).