Measurement of SLAP2 and GISP δ17O and proposed VSMOW‐SLAP normalization for δ17O and 17Oexcess. (12th February 2013)

• Record Type: Journal Article
• Authors: Schoenemann, Spruce W.; Schauer, Andrew J.; Steig, Eric J.
• Is Part Of: Rapid communications in mass spectrometry. Volume 27:Number 5(2013)
• Page Start: 582
• Page End: 590
• Publication Date: 2013-02-12
• Subjects: Mass spectrometry -- Periodicals; 543.65
• DOI: 10.1002/rcm.6486
• Languages: English
• ISSNs: 0951-4198

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <sec id="rcm6486-sec-0001" sec-type="section"> <title>RATIONALE</title> <p>The absence of an agreed‐upon <italic>δ</italic><sup>17</sup>O value for the primary reference water SLAP leads to significant discrepancies in the reported values of <italic>δ</italic><sup>17</sup>O and the parameter <sup>17</sup>O<sub>excess</sub>. The accuracy of <italic>δ</italic><sup>17</sup>O and <sup>17</sup>O<sub>excess</sub> values is significantly improved if the measurements are normalized using a two‐point calibration, following the convention for <italic>δ</italic><sup>2</sup>H and <italic>δ</italic><sup>18</sup>O values.</p> </sec> <sec id="rcm6486-sec-0002" sec-type="section"> <title>METHODS</title> <p>New measurements of the <italic>δ</italic><sup>17</sup>O values of SLAP2 and GISP are presented and compared with published data. Water samples were fluorinated with CoF<sub>3</sub>. Helium carried the O<sub>2</sub> product to a 5A (4.2 to 4.4 Å) molecular sieve trap submerged in liquid nitrogen. The O<sub>2</sub> sample was introduced into a dual‐inlet ThermoFinnigan MAT 253 isotope ratio mass spectrometer for measurement of <italic>m/z</italic> 32, 33, and 34. The <italic>δ</italic><sup>18</sup>O and <italic>δ</italic><sup>17</sup>O values were calculated after 90 comparisons with an O<sub>2</sub> reference gas.</p> </sec> <sec id="rcm6486-sec-0003" sec-type="section"> <title>RESULTS</title> <p>We propose that the accepted <italic>δ</italic><sup>17</sup>O value of SLAP be defined in terms of <italic>δ</italic><sup>18</sup>O = −55.5 ‰ and <sup>17</sup>O<sub>excess</sub> = 0, yielding a <italic>δ</italic><sup>17</sup>O value of approximately −29.6968 ‰. Using this definition for SLAP and the recommended normalization procedure, the <italic>δ</italic><sup>17</sup>O value of GISP is −13.16 ± 0.05 ‰ and the <sup>17</sup>O<sub>excess</sub> value of GISP is 22 ± 11 per meg. Correcting previous published values of GISP <italic>δ</italic><sup>17</sup>O to both VSMOW and SLAP improves the inter‐laboratory precision by about 10 per meg.</p> </sec> <sec id="rcm6486-sec-0004" sec-type="section"> <title>CONCLUSIONS</title> <p>The data generated here and compiled from previous studies provide a substantial volume of evidence to evaluate the various normalization techniques currently used for triple oxygen isotope measurements. We recommend that reported <italic>δ</italic><sup>17</sup>O and <sup>17</sup>O<sub>excess</sub> values be normalized to the VSMOW‐SLAP scale, using a definition of SLAP such that its <sup>17</sup>O<sub>excess</sub> is exactly zero. Copyright © 2013 John Wiley & Sons, Ltd.</p> </sec> </abstract>