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Correction for the 17O interference in δ(13C) measurements when analyzing CO2 with stable isotope mass spectrometry

Pure and Applied Chemistry

By:
, ,
DOI: 10.1351/PAC-REP-09-01-05

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Abstract

Measurements of δ(13C) determined on CO2 with an isotope-ratio mass spectrometer (IRMS) must be corrected for the amount of 17O in the CO2. For data consistency, this must be done using identical methods by different laboratories. This report aims at unifying data treatment for CO2 IRMS by proposing (i) a unified set of numerical values, and (ii) a unified correction algorithm, based on a simple, linear approximation formula. Because the oxygen of natural CO2 is derived mostly from the global water pool, it is recommended that a value of 0.528 be employed for the factor λ, which relates differences in 17O and 18O abundances. With the currently accepted N(13C)/N(12C) of 0.011 180(28) in VPDB (Vienna Peedee belemnite) reevaluation of data yields a value of 0.000 393(1) for the oxygen isotope ratio N(17O)/N(16O) of the evolved CO2. The ratio of these quantities, a ratio of isotope ratios, is essential for the 17O abundance correction: [N(17O)/N(16O)]/[N(13C)/N(12C)] = 0.035 16(8). The equation [δ(13C) ≈ 45δVPDB-CO2 + 2 17R/13R (45δVPDB-CO2 – λ46δVPDB-CO2)] closely approximates δ(13C) values with less than 0.010 ‰ deviation for normal oxygen-bearing materials and no more than 0.026 ‰ in extreme cases. Other materials containing oxygen of non-mass-dependent isotope composition require a more specific data treatment. A similar linear approximation is also suggested for δ(18O). The linear approximations are easy to implement in a data spreadsheet, and also help in generating a simplified uncertainty budget.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Correction for the 17O interference in δ(13C) measurements when analyzing CO2 with stable isotope mass spectrometry
Series title:
Pure and Applied Chemistry
DOI:
10.1351/PAC-REP-09-01-05
Volume
82
Issue:
8
Year Published:
2010
Language:
English
Publisher:
IUPAC
Publisher location:
Research Triangle Park, NC
Contributing office(s):
National Research Program - Eastern Branch
Description:
15 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Pure and Applied Chemistry
First page:
1719
Last page:
1733