High precision determination of 48Ca/42Ca ratio by tims for Ca isotope fractionation studies

Gopalan, Kunchithapadam ; Macdougall, J. Douglas ; Macisaac, Christopher (2007) High precision determination of 48Ca/42Ca ratio by tims for Ca isotope fractionation studies Geostandards and Geoanalytical Research, 31 (3). pp. 227-236. ISSN 1639-4488

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Official URL: http://onlinelibrary.wiley.com/doi/10.1111/j.1751-...

Related URL: http://dx.doi.org/10.1111/j.1751-908X.2007.00847.x


For studies of mass-dependent fractionation of calcium isotopes in natural materials, the 48Ca/42Ca ratio is a superior choice to the conventionally measured 44Ca/40Ca ratio for two important reasons. These are (1) mass-dependent fractionation can be determined free from the effects of inherited or ingrown radiogenic 40Ca and (2) this ratio increases the spread of measured isotopic masses by 50%, resulting in statistically better resolution of fractionation, assuming similar precision. A third, though strictly technical, advantage is the inherent ability of a mass spectrometer to measure ratios close to unity (48Ca/42Ca) more precisely than very small or large ratios (44Ca/40Ca). However, because of the very low natural abundance of both 48Ca and 42Ca, their ratio has been very difficult to measure, the only attempt so far being on a high mass resolution MC-ICP-MS with a precision of 0.33%. We report here determination of the 48Ca/42Ca ratio by the more commonly available and user-friendly multi-collector TIMS using a 43Ca-46Ca double-spike, with a significantly better precision of 0.18% (2s). The 48Ca/40Ca or 44Ca/40Ca ratio can also be measured in the same mass spectrometer run to provide complementary information on any radiogenic component.

Item Type:Article
Source:Copyright of this article belongs to International Association of Geoanalysts.
Keywords:Ca Isotopes; Mass Dependent Fractionation; Double-spike; 48Ca/42Ca Ratio; Isotopes du Calcium; Fractionnement Dependant De La Masse; Double Spike; Rapport 48Ca/42Ca
ID Code:13563
Deposited On:12 Nov 2010 15:20
Last Modified:14 Feb 2011 08:20

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