Sulfur isotope ratio measurements of individual sulfate particles by NanoSIMS

Baerbel Winterholler*, Peter Hoppe, Stephen Foley, Meinrat O. Andreae

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

32 Citations (Scopus)

Abstract

The sulfur isotopic compositions of barite (BaSO4), anhydrite (CaSO4), gypsum (CaSO4·2H2O), mascagnite ((NH4)2SO4), thenardite (Na2SO4), boetite (K2SO4), epsomite (MgSO4·7H2O), magnesium sulfate (MgSO4·xH2O) and cysteine (an amino acid) were determined with a Cameca NanoSIMS 50 ion microprobe employing a Cs+ primary ion beam and measuring negative secondary ions. This ion microprobe permits the analysis of sulfur isotope ratios in sulfates on 0.001-0.5 ng of sample material, enabling the analysis of individual S-bearing particles with diameters as small as 500 nm. The grain-to-grain reproducibility of measurements is typically 5‰ (1σ) for micron-sized grains, <5‰ for submicron-sized grains down to roughly 500 nm, and <2‰ for polished thin sections and ultra microtome sections which were studied for comparison. The role of chemical composition (matrix effect) and sample preparation technique on the instrumental mass fractionation (IMF) of the 34S/32S ratio in the NanoSIMS has been investigated for different sulfates and one amino acid. The IMF varies by ∼15‰ between the standards studied here, underlining the importance of a good understanding of the matrix-specific IMF correction in order to get precise S isotope data for very small samples such as aerosol particles. A good correlation between IMF and ionic radius of the cations in sulfates was found, permitting inference of IMF corrections for sulfates for which no isotope standards are available.

Original languageEnglish
Pages (from-to)63-77
Number of pages15
JournalInternational Journal of Mass Spectrometry
Volume272
Issue number1
DOIs
Publication statusPublished - 15 Apr 2008
Externally publishedYes

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