Damian Smeulders

International comparison CCQM-K54: Primary standard gas mixtures of hexane in methane

The aim of this comparison is to evaluate the gravimetry and purity verification of gas mixtures prepared by introducing a liquid into a gas cylinder. This type of preparation is well known from, e.g., ethanol in nitrogen/air (CCQM-K4), and n-hexane in synthetic natural gas (CCQM-K16). The choice for n-hexane in methane is based on the relevance of natural gas primary standard mixtures and higher hydrocarbons in synthetic natural gas (for, e.g., dew point calibrations). Furthermore, n-hexane is relatively straightforward to analyse using a GC/FID (gas chromatograph equipped with a flame ionisation detector) with good repeatability. Eight laboratories participated. After the data evaluation, the result of one laboratory was eliminated to arrive at a consistent subset. The quality of the fitted line was not overly good, leading to small discrepancies in the degrees-of-equivalence calculated for three other laboratories. Only four laboratories are consistent with 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 (MRA).

Final Report on International comparison CCQM K23ac: Natural gas types I and III

At the highest metrological level, natural gas standards are commonly prepared gravimetrically as PSMs (primary standard mixtures). This international key comparison is a repeat of CCQM-K1e-g. The mixtures concerned contain nitrogen, carbon dioxide and the alkanes up to butane. The only difference with CCQM-K1e-g is the addition of iso-butane to the list. The results usually agree within 1% (or better) with the key comparison reference value. For ethane, nitrogen and carbon dioxide, the agreement is within 0.5% (or better), and for methane within 0.1% (or better) 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 (MRA).

International Comparison CCQM K23b-Natural gas type II

At the highest metrological level, natural gas standards are commonly prepared gravimetrically as PSMs (Primary Standard Mixtures). This international key comparison is a repeat of CCQM-K1e-g. The mixtures concerned contain nitrogen, carbon dioxide and the alkanes up to butane. The only difference from CCQM-K1e-g is the addition of iso-butane to the list. The agreement of the results in this key comparison is very good. For all parameters, with a few exceptions, the results agree within 0.5% (or better) with the key comparison reference value. For methane, the results are generally within 0.1% (or better) 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 (MRA).

International comparison CCQM-K119 liquefied petroleum gas

M L Downey, P J Brewer, E Atkins, R J C Brown, A S Brown, E T Zalewska, A M H van der Veen, D E Smeulders, J B McCallum, R T Satumba, Y D Kim, N Kang, H K Bae, J C Woo, L A Konopelko, T A Popova, A V Meshkov, O V Efremova and Y Kustikov National Physical Laboratory, Hampton Road, Teddington, TW11 0LW, UK. Van Swinden Laboratorium, Chemistry Group, Thijsseweg 11, 2629 JA Delft, the Netherlands. National Measurement Institute, 36 Bradfield Rd, Lindfield NSW, 2070, Australia. Korea Research Institute of Standards and Science, 267 Gajeong-ro, Yuseong-gu, Daejeon 34113, Republic of Korea. D.I. Mendeleyev Institute for Metrology, 19 Moskovsky Prospekt, 198005 St-Petersburg, Russia.

International comparison CCQM-K51: Carbon monoxide (CO) in nitrogen (5 µmol mol−1)

The first key comparison on carbon monoxide (CO) in nitrogen dates back to 1992 (CCQM-K1a). It was one of the first types of gas mixtures that were used in an international key comparison. Since then, numerous national metrology institutes (NMIs) have been setting up facilities for gas analysis, and have developed claims for their Calibration and Measurement Capabilities (CMCs) for these mixtures. Furthermore, in the April 2005 meeting of the CCQM (Consultative Committee for Amount of Substance) Gas Analysis Working Group, a policy was proposed to repeat key comparisons for stable mixtures every 10 years. This comparison was performed in line with the policy proposal and provided an opportunity for NMIs that could not participate in the previous comparison. NMISA from South Africa acted as the pilot laboratory. Of the 25 participating laboratories, 19 (76%) showed satisfactory degrees of equivalence to the gravimetric reference value. The results show that the CO concentration is not influenced by the measurement method used, and from this it may be concluded that the pure CO, used to prepare the gas mixtures, was not 13C-isotope depleted. This was confirmed by the isotope ratio analysis carried out by KRISS on a 1% mixture of CO in nitrogen, obtained from the NMISA. There is no indication of positive or negative bias in the gravimetric reference value, as the results from the different laboratories are evenly distributed on both sides of the key comparison reference value. 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).

International key comparison APMP.QM-S1: Comparison of primary standards of nitrogen in helium

Gravimetry has been used as the primary method for the preparation of primary standard gas mixtures in most NMIs. In the uncertainty evaluation of primary standard gas mixtures, the purity analysis and the weighing of gases are very important. In general key comparisons, the uncertainty of analysis is bigger than that of preparation, and accurate comparison about the capability of preparation of primary standard gas mixtures is significantly difficult. In this comparison, the concentration of nitrogen has been chosen as that which can easily be analyzed using GC-TCD with small uncertainty and weighed in almost the same range for component and balance gases. Participants sent a primary standard gas mixture composed of about 12.5% mol/mol nitrogen in helium to the coordinating laboratory with the report of the purity analysis and the gravimetric preparation including raw data. The coordinating laboratory analysed each standard gas cylinder with GC-TCD and compared with reported concentration values. From the results, it was clear that there were no outliers in this comparison. Consequently, the distribution of the results is regarded as a normal distribution and an arithmetic mean was used as the reference value. The results were then analysed in terms of degrees of equivalence. 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 APMP, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

A preparative comparison using the 'harmonization' method on standards of synthetic natural gas (CCQM-P87)

Twenty-two standards of synthetic natural gas standards were submitted from ten different NMIs for a comparison using the harmonization method developed by NPL. All standards had seven components. This method can remove the correlated variation in calibration data for multi-component mixtures and makes a significant improvement in fitting individual points to calibration curves. After removing the non-random variation from the data all the standards showed very good agreement with only a few outliers. The typical deviation from the calibration curves was around 0.05% (relative) for the main components and less than 0.2% for the butanes. 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 GAWG.