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Consistency of Δ 13 C Measurements Improved



T B. Copelen, W Brand, M Gehre, M Groening, HAJ Meijer, Blaza Toman, R. Michael Verkouteren


We present state-of-the-art measurements and data evaluation methods to show that the consistency of carbon isotope ratio measurements can be improved 39 % to 47 % by anchoring the measurement scale with two isotopic reference materials differing in carbon-13 content. It is recommended that delta-13-C values of both organic and inorganic materials be measured and expressed relative to VPDB (Vienna Peedee belemnite) on a scale normalized by assigning consensus values of 46.6 per mill to L-SVEC lithium carbonate (NIST RM 8545) and +1.95 per mill to NBS 19 calcium carbonate (NIST RM 8544). Uncertainties of other reference material values on this scale are improved by factors up to two or more, and the values of some have been notably shifted. This advance should enable laboratories worldwide to achieve high standards of technical competence needed to report reproducible d13C values with reasonable and consistent uncertainties. Possible applications include the authentication of pharmaceuticals to combat counterfeiting, the resolution of megaton discrepancies in global atmospheric carbon inventories, and the harmonization of results from international laboratories that test for the use of metabolic steroids at the Olympic Games.
Analytical Chemistry


carbon, intercomparison, isotope ratio, normalization, reference materials, ring test, stable isotope, standards


Copelen, T. , Brand, W. , Gehre, M. , Groening, M. , Meijer, H. , Toman, B. and Verkouteren, R. (2006), Consistency of &#916; <sup>13</sup> C Measurements Improved, Analytical Chemistry (Accessed June 18, 2024)


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Created January 31, 2006, Updated October 12, 2021