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Preparation, Characterization, and Value Assignment of Carbon Dioxide Isotopic Reference Materials: RMs 8562, 8563, and 8564



R M. Verkouteren


Three carbon dioxide isotopic Reference Materials (RM 8562, RM 8563, and RM 8564) have been prepared and characterized for composition, heterogeneity, and stability using dual-inlet isotope ratio mass spectrometry. RMs 8562-8564 are not certified, but their use as proxies for carbonate standards allows users to realize precisely the Vienna-PDB scale, and to provide comparability of stable carbon and oxygen isotope ratio data obtained by investigators in different laboratories. Samples (ca. 400 {u}mol each) are sealed in borosilicate glass tubes (9 mm outer diameter) for distribution by the National Institute of Standards and Technology (NIST) and the International Atomic Energy Agency (IAEA).Proposed assignments of d13C and d18O values and uncertainties for the RMs were determined by two complementary methods: 1) through self-consistent (accurate) measurements of relative (?d) values between RMs (?d45CO2, ?d46CO2, and ?d47CO2), and 2) through an international comparison exercise, which allowed consensus for standardization onto the VPDB scale. The ?d values were measured at NIST, where unique instrument design and protocols were used so that measurements of d45CO2, d46CO2, and d47CO2 were self-consistent, a necessary condition of measurement accuracy. The intercomparison exercise involved thirteen international laboratories; carbonate standards were also measured to normalize the results. The proposed values (and combined standard uncertainties) for the d13CVPDB and d18OVPDB values are, respectively, -3.76%(0.03%) and -8.49%(0.11%) for RM 8562, -41.56%(0.05%) and -23.76%(0.11%) for RM 8563, and-10.45%(0.04%) and +0.19%(0.10%).Within any batch (each consisting of over one thousand samples), sample-to-sample isotopic variations (standard deviations) were measured to be less than 0.007% and 0.026% for d13C and d18O, respectively. No conclusive evidence of long-term isotopic drift in these RMs has been observed after one year of monitoring.
Analytical Chemistry
No. 20


breakseals, carbon dioxide, Finnigan, intercomparison, ion source, isotope ratio, mass spectometry, reference material, standards


Verkouteren, R. (1999), Preparation, Characterization, and Value Assignment of Carbon Dioxide Isotopic Reference Materials: RMs 8562, 8563, and 8564, Analytical Chemistry (Accessed June 18, 2024)


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Created October 1, 1999, Updated February 17, 2017