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Calcium Isotopic Reference

 δ44/40Ca Values of Calcium Isotopic Reference Materials



Nominal Unit Size

δ44/40Ca SRM915a



SRM 915a

calcium carbonate

20 g

0 ‰


† Exact value defining the delta scale.  However, for some studies, δ44/40Ca measurements may be more appropriate.


Although n(44Ca)/n(40Ca) calcium isotope-amount ratios commonly are measured to determine δ44/40Ca values, 40Ca may be a poor choice for the denominator in this ratio because it is a product of 40K radioactive decay; thus, the mole fraction of 40Ca will vary with the age and n(K)/n(Ca) ratio of a material.


21. Coplen, T. B., Böhlke, J.K., De Bièvre, P.,  Ding, T., Holden, N.E., Hopple, J. A., Krouse, H. R., Lamberty, A., Peiser, H. S., Revesz, K., Rieder, S. E., Rosman, K. J. R., Roth, E., Taylor, P. D. P., Vocke, Jr., R. D., and Xiao, Y. K., Isotope-abundance variations of selected elements, Pure Appl. Chem. 74, 1987-2002 (2002).  [full text  pdf 506 KB]  {SNIF.pdf}



2010 Commission on Isotopic Abundances and Atomic Weights | a commission of the International Union of Pure and Applied Chemistry