LAUSR

The Pilot Study CCQM-P206 was conducted in parallel with the Key Comparison CCQM-K68.2019, which was aimed at evaluating the level of comparability of laboratories' capabilities for nitrous oxide in air primary reference mixtures at ambient amount fractions, in the range 320 nmol mol−1 to 350 nmol mol−1. The Pilot Study was set up to allow the participation of the Scripps Institution of Oceanography of the University of California San Diego (SIO/UCSD) as guest expert laboratory of the CCQM. The SIO/UCSD was invited by the CCQM in view of its long experience in accurate measurements of nitrous oxide in the atmosphere and is the calibration laboratory for this compound in the AGAGE (Advanced Global Atmospheric Gases Experiment) global measurement network. The laboratory has developed a unique method which provides an independent assessment of the N2O amount fraction compared to participants in CCQM-K68.2019. Its participation was also seen as the occasion to contribute to a more general reflexion on the compared advantages of two different systems to ensure traceability: a unique scale maintained by one central laboratory, or the dissemination of materials all traceable to the SI by multiple national metrology institutes. The comparison CCQM-K68.2019 was coordinated by the BIPM and the KRISS. 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. Two independent analytical methods were used by the BIPM to analyse the amount fraction of N2O in air, namely Gas Chromatography with an Electron Capture Detector (GC−ECD) and Quantum Cascade Laser Absorption Spectroscopy (QCLAS). For the Pilot Study, SIO/UCSD provided results of measurements of the N2O amount fraction in the two standards submitted by the Global Monitoring Laboratory of the National Oceanic and Atmospheric Administration (NOAA), a participant in the Key Comparison. Therefore, this study consists in looking at the agreement between SIO/UCSD measurement results and the Key Comparison reference value. All details on the Key Comparison CCQM-K68.2019, including its protocol and its results, can be found in its report. This report focuses on SIO/UCSD results and agreement with participants in the Key Comparison. 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).