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Stable Isotope Geochemistry

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Subject:
delta conversion equation
From:
Andrew Schauer <[log in to unmask]>
Reply To:
Stable Isotope Geochemistry <[log in to unmask]>
Date:
Thu, 12 Jun 2008 09:00:20 -0700
Content-Type:
text/plain
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Hi all,

An equation for converting from a working standard scale to an international reference material scale is:

d sa/st = d sa/ws + d ws/st + 10^-3(d sa/ws * d ws/st)

where d is the delta, sa is a sample, st is the international reference material, ws is the working standard, and sa/ws is a sample relative to a working standard. This equation is found many places (e.g. W.A Brand's chapter 38 (p855) in Handbook of Stable Isotope Analytical Techniques (ed. P.A. de Groot)). My question is, what is the derivation of the final term:

10^-3(d sa/ws * d ws/st)

The term clearly deals with those samples and standards that are very different from one another, as it is larger the more disparate samples and standards are. Searching the IsoGeoChem archives shows that many folks leave off this term. Thank you all for your help.

andy



 Andrew Schauer
ISOLAB
Department of Earth and Space Sciences
University of Washington
Seattle, WA 98195


206.543.6327
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