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Durham University

Department of Earth Sciences

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Publication details for Dr Geoff Nowell

G.M. Nowell, A. Luguet, D.G. Pearson & M.A. Horstwood (2008). Precise and accurate 186Os/188Os and 187Os/188Os measurements by Multi- Collector Plasma Ionisation Mass Spectrometry (MC-ICP-MS) part I: solution analyses. Chemical Geology 248: 363-393.
  • Publication type: Journal Article

Author(s) from Durham

Abstract

We present new high precision Os isotope data obtained by solution-mode MC-ICPMS
for 4 different Os isotope standards and compare the data to that obtained by the N-TIMS
method. Mass fractionation effects for MC-ICPMS are evaluated and we demonstrate excellent
adherence to the exponential law. An improved and robust method for the derivation of
interfering element isotope ratios is presented and evaluated via analysis of solutions with widely
varying interfering element/analyte ratios. We show experiments that illustrate the extent of
memory with a conventional solution introduction system and establish a protocol that reduces
washout time and memory effects to the same level as those common for other elements typically
analysed at high precision by MC-ICPMS.
Data for standard solutions show excellent agreement between MC-ICPMS and N-TIMS
for all Os isotope ratios except 186Os/188Os and 184Os/188Os which are consistently lower by ~100
ppm and 3-5 ‰ respectively for MC-ICPMS. These differences are highly unlikely to arise from
problems relating to Faraday cup efficiency variations, residual mass fractionation effects or
inaccuracies in the applied W interference corrections on 186Os and 184Os for MC-ICPMS
analyses. These issues require further investigation if the Pt-Os system is to find routine
application as a geochemical tracer.