The performance of single and multi-collector ICP-MS instruments for fast and reliable34S/32S isotope ratio measurements.
The performance and validation characteristics of different single collector inductively coupled plasma mass spectrometers based on different technical principles (ICP-SFMS, ICP-QMS in reaction and collision modes, and ICP-MS/MS) were evaluated in comparison to the performance of MC ICP-MS for fast and reliable S isotope ratio measurements. The validation included the determination of LOD, BEC, measurement repeatability, within-lab reproducibility and deviation from certified values as well as a study on instrumental isotopic fractionation (IIF) and the calculation of the combined standard measurement uncertainty. Different approaches of correction for IIF applying external intra-elemental IIF correction (aka standard-sample bracketing) using certified S reference materials and internal inter-elemental IIF (aka internal standardization) correction using Si isotope ratios in MC ICP-MS are explained and compared. The resulting combined standard uncertainties of examined ICP-QMS systems were not better than 0.3-0.5% (uc,rel), which is in general insufficient to differentiate natural S isotope variations. Although the performance of the single collector ICP-SFMS is better (single measurementuc,rel= 0.08%), the measurement reproducibility (>0.2%) is the major limit of this system and leaves room for improvement. MC ICP-MS operated in the edge mass resolution mode, applying bracketing for correction of IIF, provided isotope ratio values with the highest quality (relative combined measurement uncertainty: 0.02%; deviation from the certified value: <0.002%).
University of Natural Resources and Life Sciences, Vienna, Department of Chemistry, VIRIS Laboratory, Konrad-Lorenz-Straße 24, 3430 Tulln, Austria.|University of Natural Resources and Life Sciences, Vienna, Department of Forest- and Soil Sciences, Institute of Forest Ecology, Peter-Jordan-Straße 82, 1190 Vienna, Austria.
Ondrej
O
Hanousek
University of Natural Resources and Life Sciences, Vienna, Department of Chemistry, VIRIS Laboratory, Konrad-Lorenz-Straße 24, 3430 Tulln, Austria.
Marion
M
Brunner
Department of Marine Bioanalytical Chemistry, Institute of Coastal Research, Helmholtz-Centre for Materials and Coastal Research, Max-Planck-Straße 1, 21502 Geesthacht, Germany.
Daniel
D
Pröfrock
Department of Marine Bioanalytical Chemistry, Institute of Coastal Research, Helmholtz-Centre for Materials and Coastal Research, Max-Planck-Straße 1, 21502 Geesthacht, Germany.
Johanna
J
Irrgeher
University of Natural Resources and Life Sciences, Vienna, Department of Chemistry, VIRIS Laboratory, Konrad-Lorenz-Straße 24, 3430 Tulln, Austria.
Thomas
T
Prohaska