The key comparison CCQM-K65 was intended to compare the capabilities for the preparation and value assignment of gas standards for methyl and ethyl mercaptans in methane, maintained at the participating national metrological institutes: VNIIM (Russia), KRISS (Korea), VSL (Netherlands) and NPL (United Kingdom). The range of the nominal amount of substance fractions of the comparison gas mixtures was 20 µmol/mol to 30 µmol/mol, which is close to regulatory level (in several countries including Russia) for mercaptans in odorated natural gas. This comparison was proposed at the 12th GAWG meeting in October 2004 and was conducted in 2008.Conclusions are as follows: The results of all laboratories are consistent with the reference values. The observed differences between the reference and reported values are within ±0.9% for methyl mercaptan and ±0.75% for ethyl mercaptan relative to the gravimetric values, and do not exceed the appropriate assigned expanded uncertainties. The prepared mixtures were found to be stable during about a year within the uncertainty of the measurements. The gravimetric values were successfully validated with a dynamic method. 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 aim of this comparison was to compare capabilities for the preparation and value assignment of gas mixture standards for benzene, chloroform, dichloromethane, trichloroethylene, tetrachloroethylene, 1,2-dichloroethane, 1,3-butadiene and vinyl chloride in nitrogen (HAPs-8), maintained at national metrology institutes (NMIs). The measurements in this key comparison took place in 2003. There were six 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 nmol/mol to 110 nmol/mol. The Chemical Evaluation Research Institute (CERI, Japan) prepared gravimetric mixture samples of HAPs-8 in 10 L aluminium cylinders and the homogeneity and long term stability of these samples were evaluated at CERI before and after the shipment of the cylinders to the participants. Each participating laboratory was shipped one cylinder to be analysed and then returned to the CERI. Each sample was reanalysed to verify whether the contents were stable throughout the comparison. These measurements showed no significant change in the amount fraction within the estimated uncertainty of the measurements except for 1,2-dichroloethane. These deviations were combined into the uncertainty of the comparison samples but were small enough compared to the deviations from values reported by participating laboratories and the gravimetric values of the samples.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).

Industrial stack gas emission measurements are important for process control, control of air pollution, and for implementing legislation regarding carbon dioxide emission rights. Measurements are typically performed using a range of process analysers for carbon monoxide (CO), carbon dioxide (CO2), nitrogen oxides (NOx), sulphur dioxide (SO2) and miscellaneous hydrocarbons. The calibration of these analysers is often performed using a series of binary mixtures of each component in nitrogen. For reasons of efficiency as well as a better match with true stack gas, the use of multi-component mixtures for this purpose would be preferred.The aim of this key comparison is to evaluate the measurement capabilities of national metrology institutes for carbon monoxide, carbon dioxide, nitrogen monoxide, sulphur dioxide and propane in nitrogen. Ten laboratories participated in the key comparison and one in the associated study. The key comparison reference value is based on the gravimetric preparation data.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).