Letter to the Editor: New values for silicon reference materials, certified for isotope abundance ratios

Abstract

New isotope abundance and relative atomic mass (atomic weight) values — with low, hitherto unattained uncertainty — are reported for two previously described silicon reference materials using a well-known method with an improved isotope-ratio mass spectrometer. These new values are directly traceable to the SI, more specifically to the unit for amount of substance, the mole, and independent of the SI unit of mass and of the Avogadro constant. Besides the residual mass-spectrometric uncertainties, these new values depend in effect only on a recently published direct comparison of the cyclotron frequency in a Penning trap of 28 Si + with that of 12 C + .

Atomic weights of the elements 2013 (IUPAC Technical Report)

“…The δ 26/24 Mg scale and 26 Mg amount-fraction scales were matched using data from [32]. The expanded uncertainty in matching the atomic-weight and Si scale, for completeness) and 30 Si amount-fraction scale were matched using the data of De Bièvre et al [33] and a δ 30 Si value for IRMM-017 of -1.3 ‰ relative to NBS 28 [26]. The expanded uncertainty in the atomic-weight and 30 Si amount-fraction scales with the δ Cl amount-fraction scale were matched using the data of Shields et al [35] and Xiao et al [36].…”

Atomic weights of the elements. Review 2000 (IUPAC Technical Report)

“…Therefore, in 1983 [11] CAWIA added the annotation "r" because a more precisely stated standard atomic weight with a single-digit uncertainty would conflict with the actual sample atomic weights of possible sources of Si. In 1991 and 1994, CAWIA noted that, while new values with considerably smaller uncertainties (uncertainty 0.000 12 on an atomic-weight value of 28.085 65) had been determined on Si isotopic reference materials [247,248], the range in isotopic composition of normal terrestrial materials prevent a more precise standard atomic weight being given. δ 30 Si measurements are expressed relative to NBS 28 SiO 2 as distributed by IAEA and NIST.…”

Isotope-abundance variations and atomic weights of selected elements: 2016 (IUPAC Technical Report)

“…The lower and upper bounds of the isotope-delta values of the selected substances and materials are compiled in Tables 1-12. Si scale, for specification with two isotopes) and 30 Si amount-fraction scale were matched using the data of De Bièvre et al [30] and a δ…”

“…The expanded uncertainty in the atomic-weight and 30 Si amount-fraction scales with the δ Cl amount-fraction scale were matched using the data of Shields et al [32] and Xiao et al [33]. The expanded uncertainty in the atomic-weight and 37 Cl amount-fraction scales with the δ…”