Premium
Grain‐scale heterogeneities in the stable carbon and oxygen isotopic compositions of the international standard calcite materials (NBS 19, NBS 18, IAEA‐CO‐1, and IAEA‐CO‐8)
Author(s) -
Ishimura Toyoho,
Tsunogai Urumu,
Nakagawa Fumiko
Publication year - 2008
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.3571
Subject(s) - calcite , delta , chemistry , homogeneous , stable isotope ratio , analytical chemistry (journal) , isotopes of oxygen , oxygen 18 , carbon fibers , accelerator mass spectrometry , mineralogy , mass spectrometry , nuclear chemistry , environmental chemistry , materials science , chromatography , nuclear physics , thermodynamics , physics , composite number , composite material , astronomy
We determined grain‐scale heterogeneities (from 6 to 88 µg) in the stable carbon and oxygen isotopic compositions ( δ 13 C and δ 18 O) of the international standard calcite materials (NBS 19, NBS 18, IAEA‐CO‐1, and IAEA‐CO‐8) using a continuous‐flow isotope ratio mass spectrometry (CF‐IRMS) system that realizes a simultaneous determination of the δ 13 C and the δ 18 O values with standard deviations (S.D.) of less than 0.05‰ for CO 2 gas. Based on the S.D. of the δ 13 C and δ 18 O values determined for CO 2 gases evolved from the different grains of the same calcite material, we found that NBS 19, IAEA‐CO‐1, and IEAE‐CO‐8 were homogeneous for δ 13 C (less than 0.10‰ S.D.), and that only NBS 19 was homogeneous for δ 18 O (less than 0.14‰ S.D.). On the level of single grains, we found that both IAEA‐CO‐1 and IAEA‐CO‐8 were heterogeneous for δ 18 O (1.46‰ and 0.76‰ S.D., respectively), and that NBS 18 was heterogeneous for both δ 13 C and δ 18 O (0.34‰ and 0.54‰ S.D., respectively). Closer inspection of NBS 18 grains revealed that the highly deviated isotopic compositions were limited to the colored grains. By excluding such colored grains, we could also obtain the homogeneous δ 13 C and δ 18 O values (less than 0.18‰ and less than 0.16‰ S.D., respectively) for NBS 18. We conclude that NBS 19, IAEA‐CO‐1, or pure grains in NBS 18 are suitable to be used as the standard reference material for δ 13 C, and that either NBS 19 or pure grains in NBS 18 are suitable to be used as the reference material for δ 18 O during the grain‐scale isotopic analyses of calcite. Copyright © 2008 John Wiley & Sons, Ltd.