Hannover 2020 – scientific programme

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MS: Fachverband Massenspektrometrie

MS 1: Precision Mass Spectrometry I

MS 1.4: Talk

Monday, March 9, 2020, 12:00–12:15, f128

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 (PTB), Braunschweig, Germany

After the revision of the SI units in 2019, one of the two main methods to realize and disseminate the kilogram and mole is the the X-ray-crystal-density (XRCD) method [1-3]. Here, silicon atoms in a silicon sphere are counted combining the measurements of the volume, the lattice parameter, the surface condition, 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) [4]. 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 and how this has been, is, and will be treated in the near future combining established and new experimental techniques with special emphasis on the mass resolution of the mass spectrometer. The target uncertainty is u(M) < 5 x 10-9 in case of enriched silicon and u(M) < 5 x 10-6 for natural silicon.

[1] K. Fujii et al., Metrologia, 53, A19 (2016). [2] D. Knopf et al., Metrologia, 56, 024003 (2019). [3] B. Güttler, O. Rienitz, A. Pramann, Annalen der Physik, 1800292 (2018). [4] A. Pramann, T. Narukawa, O. Rienitz, Metrologia, 54, 738 (2017).