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MS: Fachverband Massenspektrometrie

MS 1: Precision Mass Measurements I

MS 1.6: Vortrag

Montag, 20. September 2021, 12:15–12:30, H3

Reduction of Measurement Uncertainty in MC-ICP-MS: A Precondition for the Dissemination of the SI Units Kilogram and Mole — •Axel Pramann and Olaf Rienitz — Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany

After the revision of the SI units in May 2019, one of the two methods to realize and disseminate the kilogram and mole is the the X-ray-crystal-density (XRCD) method (1-2). Here, silicon atoms in a silicon sphere are *counted* combining the measurements of the volume, the lattice parameter, the surface properties, and the isotopic composition using the fixed Avogadro constant. A key experiment uses high resolution multicollector inductively coupled plasma mass spectrometry (HR-MC-ICP-MS) to measure isotope ratios in natural and in 28Si enriched silicon to determine the respective molar mass (M) (3). It is shown how the measurement uncertainty of the isotope ratios according to the *Guide to the Expression of Uncertainty in Measurement* influences the results when using natural or enriched silicon and how this has been, is, and will be treated in the near future combining established and new experimental techniques (4).

(1) K. Fujii et al., Metrologia, 53, A19 (2016). (2) B. Guettler, O. Rienitz, A. Pramann, Annalen der Physik, 1800292 (2018). (3) A. Pramann, T. Narukawa, O. Rienitz, Metrologia, 54, 738 (2017). (4) A. Pramann, J. Vogl, O. Rienitz, MAPAN J. Metrol. Soc. I, 35, 499 (2020).