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Issue 6, 2013
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Platinum stable isotope ratio measurements by double-spike multiple collector ICPMS

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Abstract

We present a new technique for the precise determination of platinum (Pt) stable isotope ratios by multiple-collector inductively coupled plasma mass spectrometry (MC-ICPMS) using two different Pt double-spikes (192Pt–198Pt and 196Pt–198Pt). Results are expressed relative to the IRMM-010 Pt isotope standard as the parts per million difference in 198Pt/194PtPt ratios (μ198Pt). Repeated measurements of the IRMM-010 Pt standard in two different laboratories, consuming ca. 40–85 ng of Pt, show that a long-term external reproducibility for μ192Pt of ≤40 ppm (2 sd; equivalent to ≤10 ppm u−1, where u is the unified atomic mass unit) can be obtained on Pt stable isotope ratios with either double-spike. Elemental doping tests reveal that double-spike corrected Pt stable isotope ratios are insensitive to the presence of relatively high (up to 10%) levels of matrix elements, although the 192Pt–198Pt double-spike is affected by an isobaric interference on 192Pt from 192Os. The 196Pt–198Pt double-spike does not use 192Pt in the double-spike inversion and is unaffected by Os contamination, and is our recommended double-spike for use with natural samples. As part of this study, we re-determined the natural Pt isotopic composition of IRMM-010 by MC-ICPMS using external element (Pb) doping to correct for instrumental mass bias and have identified relative Pt isotope differences of up to 10% from the reference values for this standard. The new isotopic composition of the IRMM-010 standard (190Pt = 0.01289%, 192Pt = 0.7938%, 194Pt = 32.81%, 195Pt = 33.79%, 196Pt = 25.29% and 198Pt = 7.308%) results in a redefined Pt atomic weight of 195.08395 ± 0.00068. Using our technique we have measured small, reproducible and statistically significant offsets in Pt stable isotope ratios between different Pt element standards and the IRMM-010 standard, which potentially indicates that natural Pt stable isotope fractionations exist that are larger than the reproducibility of our technique.

Graphical abstract: Platinum stable isotope ratio measurements by double-spike multiple collector ICPMS

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Publication details

The article was received on 23 Jan 2013, accepted on 04 Mar 2013 and first published on 04 Mar 2013


Article type: Paper
DOI: 10.1039/C3JA50022E
Citation: J. Anal. At. Spectrom., 2013,28, 853-865
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    Platinum stable isotope ratio measurements by double-spike multiple collector ICPMS

    J. Creech, J. Baker, M. Handler, M. Schiller and M. Bizzarro, J. Anal. At. Spectrom., 2013, 28, 853
    DOI: 10.1039/C3JA50022E

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