A More Accurate Molar Mass of Silicon via High Resolution MC-ICP-Mass Spectrometry

Abstract

High resolution multicollector inductively coupled plasma mass spectrometry (HR-MC-ICP-MS) was applied for the determination of the isotopic composition and molar mass of a silicon crystal material (“Si28”) highly enriched in the

Improved measurement results for the Avogadro constant using a28Si-enriched crystal

“…However, given that this homogeneity study incorporated most of the state-of-the art improvements in the measurement of Si isotope-amount-ratios developed since 2011, the average and individual molar masses as well as the Si isotope amount fractions derived from these data are presented in tables 1 and 2. The (VE) IDMS approach [19] was used for measuring the molar mass, with the main experimental details given in [13,15]. All measurements have been made on a commercial MC ICP-MS (Nep-tune™, Thermo Fisher Scientific).…”

“…In summary, the basis for the average molar mass of the AVO28 boule, with its associated uncertainty, was derived from molar mass measurements using TMAH as solvent and diluent. The individual molar masses of five crystal samples from part 4 (PTB [18, this paper]), one crystal from part 5 (PTB [15]), two crystals from part 5 (NMIJ [16]), two crystals from part 5 (NIST [17]), five crystals from part 7 (PTB [18, this paper]), one crystal from part 8 (PTB [15]), two crystals from part 8 (NMIJ [16]), two crystals from part 8 (NIST [17]) and four crystals from part 9 (PTB [18, this paper]) were used. These data allow a robust molar mass to be calculated for updating the Avogadro constant that is based on 24 different sample crystals spread longitudinally across the AVO28 boule and measured by three different NMIs, each employing a different experimental approach (table 2).…”

Realization of the kilogram by the XRCD method

“…A third possible blend is prepared using materials y and w (blend b3). The set of two K-factors is chosen from an over-determined system of 12 possible K-factor pairs [45,46,52]. The selection of the K 2 /K 3 pair is based on an uncertainty analysis where all the results using data from all three blends were calculated.…”

Determination of the Avogadro constant by the XRCD method using a28Si-enriched sphere

“…For the N A determination by IAC in 2015, the molar mass M of AVO28-S5c was measured independently by the Physikalisch-Technische Bundesanstalt of Germany (PTB), NIST and NMIJ using isotope dilution and multicollector inductively coupled plasma mass spectrometers [28][29][30][31]. The measured amount of substance of 30 Si was confirmed by the measurement results with instrumental neutron activation analysis (INAA) by INRIM [32].…”