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Published March 2011 | public
Journal Article

An Isotope Dilution ICP-MS Method for the Determination of Mg/Ca and Sr/Ca Ratios in Calcium Carbonate

Abstract

Mg/Ca and Sr/Ca ratios in calcium carbonate are important components of many palaeoclimate studies. We present an isotope dilution method relying on a single mixed spike containing ^(25)Mg, ^(43)Ca and ^(87)Sr. Dozens of samples per day, as small as 10 μg of carbonate, could be dissolved, spiked and run in an ICP-MS with a precision of 0.8% (2 RSD). Two instruments types, a sector field and a quadrupole ICP-MS, were compared. The best long term precision found was 0.4% (2 RSD), although this increased by up to a factor of two when samples of very different Mg or Sr content were run together in the same sequence. Long term averages for the two instruments concurred. No matrix effects were detected for a range of Ca concentrations between 0.2 and 2 mmol l^(-1). Accuracy, tested by measuring synthetic standard solutions, was 0.8% with some systematic trends. We demonstrate the strength of this isotope dilution method for (a) obtaining accurate results for sample sets that present a broad Mg and Sr range and (b) testing solid carbonates as candidate reference materials for interlaboratory consistency. Mg/Ca and Sr/Ca results for reference materials were in good agreement with values from the literature.

Additional Information

© 2010 The Authors. Geostandards and Geoanalytical Research © 2010 International Association of Geoanalysts. Received 05 Jan 09; Accepted 07 Aug 09. Article first published online: 15 Sep. 2010. This work was supported by the National Science Foundation, Grants OCE-0096373 and OCE-0502642, and the Comer Science and Education Foundation, Grant CM113. We acknowledge two anonymous reviewers for comments and suggestions than improved this manuscript.

Additional details

Created:
September 14, 2023
Modified:
October 23, 2023