The key comparison CCQM-K137 was aimed at evaluating the level of compatibility of laboratories' preparative capabilities for gravimetric nitrogen monoxide/nitrogen primary reference mixtures at mole fractions of 30 μmol mol-1 and 70 μmol mol-1. The comparison was organised by the BIPM. It consisted in the simultaneous comparison of a suite of 2n primary gas standards, two standards to be prepared by each of the n participating laboratories at the nominal values of 30 μmol mol-1 and 70 μmol mol-1. Two independent analytical methods were used by the BIPM to analyse the amount fraction of nitrogen monoxide (NO) in nitrogen; UV spectrophotometry and chemiluminescence (CLD). The agreement between the results obtained with the two main techniques served to highlight possible issues in the preparation of the standards. During this comparison, standards prepared by two participants appeared to result in a larger bias between the analysers than observed for others. These observations were explained by the analysis of all standards by Fourier Transform Infrared Spectroscopy (FTIR) which identified the presence of a larger amounts of water vapour (H2O), nitrous oxide (N2O) and nitrogen dioxide (NO2) in these standards, which are the three main impurities which can appear in mixtures of NO in nitrogen. The above observations were used to underpin the selection of standards (at each nominal NO mole fraction) which can be considered as a consistent set, allowing the calculation of a calibration line by a Generalised Least-Square regression. Key Comparison Reference Values were then proposed for all participants as predicted values from the calibration lines. Interferences caused in the response of the CLD analyser by impurities (verified by FTIR measurements) led to only the results from the UV analyser being proposed for the KCRV and Degrees of Equivalence calculations. Good agreement was observed between all participants who could prepare their standards with minimum levels of impurities. The key comparison CCQM-K137 is considered to present an analytical challenge at both nominal mole fractions and therefore considered as a Specialised (Track C) comparison in the CCQM nomenclature. 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).

This document describes the result of a key comparison for propane in nitrogen. The nominal amount-of-substance fraction of propane is 1000 μmol/mol. The comparison aimed to assess the measurement capability of participants in gas analysis. Nine NMIs or DIs participated in the comparison. CERI participated in a key comparison CCQM-K111—propane in nitrogen, and coordinated this key comparison. Therefore, every participants' results of this comparison are linking to the CCQM-K111. Gravimetric values of the samples were used as key comparison reference values (KCRVs). Measured values of eight participants were within ± 0.25 % of the KCRVs. Many participants reported purity or impurity analysis of materials. These results are also able to assess the participants' capability of the analysis. 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).

Main text CCQM-K3.2019 was a repeat of the key comparison CCQM-K3 on the composition of automotive exhaust gases. New in CCQM-K3.2019 was the addition of the amount fraction oxygen to the programme. The key comparison reference values were obtained independently, using static gravimetry and appropriate corrections from purity analysis. The key comparison results show equivalence between the measurement standards maintained by the participating national metrology institutes. The demonstrated equivalence can be used to underpin services related to automotive exhaust gases as well as generically through the flexible scheme ("track A"). 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 https://www.bipm.org/kcdb/. 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).

Benzene, toluene, ethylbenzene, o-xylene, m-xylene, and styrene (subsequently referred to gas BTEX) are volatile organic compounds emitted from gasoline, fossil fuel combustion, paints, rubber products, and adhesives. Exposure to BTEX can make adverse health effects on humans. Therefore, BTEX in both ambient and indoor air is regulated and monitored to protect public health. For this supplementary comparison, a multicomponent mixture of BTEX in nitrogen has been chosen at an amount-of-substance fraction level of 100 nmol mol−1 that is more close to their emission levels from new buildings and construction materials. The supplementary comparison is designed to underpin calibration capabilities using BTEX gas mixtures that are prepared gravimetrically as transfer standards. 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).

This key comparison aims to assess the core capabilities of the participants in gas analysis. Such competences include, among others, the capabilities to prepare primary standard gas Mixtures (PSMs), perform the necessary purity analysis on the materials used in the gas mixture preparation, the verification of the composition of newly prepared PSMs against existing ones, and the capability of calibrating the composition of a gas mixture. According to the Strategy for Key Comparisons of the Gas Analysis Working Group, this key comparison is classified as a track A key comparison, which means that the results of this key comparison can be used to underpin calibration and measurement capabilities using the flexible scheme, and for propane under the default scheme. The artefacts were binary mixtures of propane in nitrogen at a nominal amount-of-substance fraction level of 1000 μmol/mol. The values and uncertainties from the gravimetric gas mixture preparation were used as key comparison reference values (KCRVs). Each transfer standard had its own KCRV. The results are generally good. All results but one are within ± 0.2 % of the KCRV. 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).