Resolving the Germanium Atomic Weight Disparity Using Multicollector ICPMS

Abstract

Two most recent mass spectrometric measurements of natural isotopic composition germanium gave discordant Ge atomic weight values of 72.6276(64) k=2 and 72.6390(69) k=2 , respectively, a decade ago. Each measurement was performed with a different mass spectrometry platform, gas source isotope ratio mass spectrometry and thermal ionization mass spectrometry, respectively. Herein we report results obtained by multicollector inductively coupled plasma mass spectrometry yielding an atomic weight of germanium 72.6296(19) k=2 which is in support of the upcoming 2009 Standard Atomic Weight adjustment by IUPAC. Germanium isotope ratios were calibrated using a regression mass bias correction model and NIST SRM 994 gallium isotopic reference material. In this model, no assumptions are made regarding the mass bias differences between gallium and germanium or between the isotopes of germanium. Isotope ratios of 0.5620(21), 0.7515(16), 0.2125(7) and 0.2121(12) were obtained for n( 70

Assessment of international reference materials for isotope-ratio analysis (IUPAC Technical Report)

“…Stable isotope-ratio measurements using MC-ICP-MS have recently found a wider interest [206,[208][209][210][211]. While all isotopes can be used for stable isotope studies, subtle isotopic variations require an uncertainty of better than 0.1 ‰ using the R( 74 Ge/ 70 Ge) ratio; both isotopes have a relatively high abundance, and they exhibit the largest atomic mass difference.…”

Atomic weights of the elements 2011 (IUPAC Technical Report)

“…The Commission has changed the recommended value for the standard atomic weight of germanium, A r (Ge), from 72.63(1) to 72.630(8) based on an evaluation published by Yang and Meija [29]. A loglinear regression mass-bias correction using NIST SRM 994 gallium isotopic reference material enabled an improvement in the uncertainty of the atomic-weight value compared to the previous value of A r (Ge) = 72.63 (1), assigned by the Commission in 2009 [9].…”

Observations of Large Mass-Independent Fractionation Occurring in MC-ICPMS: Implications for Determination of Accurate Isotope Amount Ratios

“…More details regarding the characterization of mercury and germanium can be found in our recent studies devoted entirely to these isotopic systems. 13,14 Samples were introduced into the plasma in a self-aspiration mode at a flow rate of 50 μL min À1 . Intensities of analyte and internal standard isotopes and all other measured isotopes of interest (see below) obtained from corresponding blank solutions of 2% HNO 3 , 1% HNO 3, and 1% HCl or 2% HCl, each containing 1 mM BrCl, were subtracted from those of all samples.…”