Natural gas is an important energy vector. The determination of its composition is often used as the basis for the calculation of the calorific value. The calorific value in turn is one of the two key parameters used in natural gas trade. In the first series of key comparisons (CCQM-K1e-g), natural gas was already included with three different compositions. These mixtures contained carbon dioxide, nitrogen, ethane, propane and n-butane in methane (matrix) and were only to a limited extent representative of real natural gas. In the past years, national metrology institutes have broadened the range of components by including, e.g., i-butane, neo-pentane, n-pentane, i-pentane and n-hexane. Based on this extended components list, two new mixtures have been defined, one characteristic for a low calorific mixture (type IV) and the other for a high calorific mixture (type V). In the low calorific mixture, helium was also present. Due to presence of the butane and pentane isomers, the mixtures of type IV and V are more demanding with respect to the separation technique than the mixtures used in CCQM-K1e-g.The measurements in this key comparison took place in 2001. There were eight participants and two coordinating laboratories. The key comparison reference value (KCRV) was based on the gravimetric preparation for all components. Even for the heavier hydrocarbons (pentanes and n-hexane) the effects of, e.g., adsorption can be controlled to such an extent that this approach is still valid. The uncertainty evaluation of the KCRVs reflected also the extent to which the preparation data could be demonstrated to be valid. The validity of the preparation data was demonstrated by comparing the composition of the mixtures prepared for this comparison with measurement standards maintained by the coordinating laboratories.The key comparisons demonstrated that the results of the laboratories agreed within 1% relative to the reference value for most components. Even better agreement was obtained for nitrogen in the low calorific mixture (0.5%), carbon dioxide (0.5%), ethane (0,5%), propane (0.5%) and methane (0.1%). In some cases, larger differences were observed, which then also exceeded the associated expanded uncertaintyMain 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 Mutual Recognition Arrangement (MRA).

We report a pilot study organized within the Consultative Committee for Amount of Substance (CCQM), in which the ozone reference standards of 23 institutes have been compared to one common reference, the BIPM ozone reference standard, in a series of bilateral comparisons carried out between July 2003 and February 2005. The BIPM, which maintains as its reference standard a standard reference photometer (SRP) developed by the National Institute of Standards and Technology (NIST, United States), served as pilot laboratory. A total of 25 instruments were compared to the common reference standard, either directly (16 comparisons) or via a transfer standard (9 comparisons). The comparisons were made over the ozone mole fraction range 0 nmol/mol to 500 nmol/mol.Two reference methods for measuring ozone mole fractions in synthetic air were compared, thanks to the participation of two institutes maintaining a gas-phase titration system with traceability of measurements to primary gas standards of NO and NO2, while the 23 other instruments were based on UV absorption.In the first instance, each comparison was characterized by the two parameters of a linear equation, as well as their related uncertainties, computed with generalized least-squares regression software. Analysis of these results using the Birge ratio indicated an underestimation of the uncertainties associated with the measurement results of some of the ozone standards, particularly the NIST SRPs.As a final result of the pilot study, the difference from the reference value (BIPM-SRP27 measurement result) and its related uncertainty were calculated for each ozone standard at the two nominal ozone mole fractions of 80 nmol/mol and 420 nmol/mol.Main text. To reach the main text of this paper, click on Final Report.The final report has been peer-reviewed and approved for publication by the CCQM.

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This report presents the results of CCQM-K93, a key comparison between 13 National Measurement Institutes (NMIs), which tested the capability of the NMIs to prepare standard gas mixtures of ethanol at a nominal amount fraction of 120 µmol/mol in nitrogen. This composition is typical of the levels used to calibrate evidential breath analysers in many countries. Such standards fulfill the agreed requirements of the International Organization of Legal Metrology (OIML) for the calibration of evidential breath-alcohol analysers.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).

Ammonia is an important compound in the chemical industry. It is widely used and is the basis for producing other compounds containing nitrogen. Ammonia is also very hazardous, and consequently emissions of ammonia need be controlled and monitored. In the past years, several national metrology institutes have developed facilities for the preparation of Primary Standard gas Mixtures (PSMs), dynamically generated ammonia mixtures and facilities for comparing and certifying gas mixtures containing ammonia.The amount-of-substance fraction level of ammonia chosen for this key comparison is 30–50 µmol/mol. The results of this key comparison revealed that there is at present no consensus among static and dynamic techniques for gas mixture preparation for this component in this range. As key comparison reference value (KCRV), the mean of the three methods is used. In its uncertainty, no allowance is made for the observed biases. With respect to the KCRV, only two laboratories report consistent results. When grouped in accordance with the employed methods, the results are consistent. Further experimental work is needed.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).