Botha, Angelique and Rensburg, Mellisa Janse van and Tshilongo, James and Gupta, Prabhat K. and Johri, P. (2010) International comparison CCQM-K51: Carbon monoxide (CO) in nitrogen (5 µmol mol−1). Metrologia, 47 (Supp-1). pp. 1-97. ISSN 1681-7575

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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.

Item Type: Article
Subjects: Instruments/ Instrumentation
Depositing User: Ms Neetu Chandra
Date Deposited: 08 May 2012 11:21
Last Modified: 08 May 2012 11:21

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