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High‐precision measurements of δ 17 O and 17 O excess of NBS19 and NBS18
Author(s) -
Barkan Eugeni,
Musan Israela,
Luz Boaz
Publication year - 2015
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.7378
Subject(s) - chemistry , analytical chemistry (journal) , isotope , isotopes of oxygen , isotope ratio mass spectrometry , normalization (sociology) , oxygen 18 , δ18o , mass spectrometry , stable isotope ratio , environmental chemistry , nuclear chemistry , chromatography , nuclear physics , physics , sociology , anthropology
Rationale Measurements of oxygen‐17 excess ( 17 O excess ) in carbonates have become of great importance. However, to compare results obtained by different laboratories, it is necessary to normalize them to international standards. With this purpose in mind, we measured accurate and high precision δ 17 O and 17 O excess values for NBS19 and NBS18, two international standards, for which δ 18 O values are already widely used as the references for carbonates. Methods The measurements are based on isotopic exchange at steady state between O 2 and CO 2 over hot platinum sponge at 750°C. Dual‐inlet isotope ratio mass spectrometry (IRMS) measurements of the δ 17 O and δ 18 O values of this O 2 allow δ 17 O values of CO 2 to be obtained with very high precision (0.01 to 0.03 ‰) and, correspondingly, accurate 17 O excess values with a precision of 5 per meg. Results We measured, for the first time, the δ 17 O values and 17 O excess of CO 2 liberated from NBS19 at 25°C (39.196 ± 0.026; 20.276 ± 0.015 ‰ and −227 ± 4 per meg, respectively) and NBS18 (17.591 ± 0.041 ‰; 9.253 ± 0.018 ‰ and 3 ± 5 per meg, respectively). The values are given versus VSMOW. Conclusions Accurate values of δ 17 O and 17 O excess of the international standards NBS19‐CO 2 and NBS18‐CO 2 are now available. The new values should be used for normalization of measured oxygen isotope ratios of carbonates to allow meaningful comparison of results among different laboratories. Copyright © 2015 John Wiley & Sons, Ltd.