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An Isotope Dilution ICP‐MS Method for the Determination of Mg/Ca and Sr/Ca Ratios in Calcium Carbonate
Author(s) -
Fernandez Diego P.,
Gag Alex C.,
Adkins Jess F.
Publication year - 2011
Publication title -
geostandards and geoanalytical research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.037
H-Index - 73
eISSN - 1751-908X
pISSN - 1639-4488
DOI - 10.1111/j.1751-908x.2010.00031.x
Subject(s) - isotope dilution , dilution , carbonate , chemistry , isotope , calcium carbonate , isotopes of calcium , analytical chemistry (journal) , matrix (chemical analysis) , mineralogy , isotopes of strontium , strontium , calcium , environmental chemistry , mass spectrometry , chromatography , physics , organic chemistry , quantum mechanics , thermodynamics
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.