## ISOGEOCHEM@LIST.UVM.EDU

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Re: delta conversion equation

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Fri, 13 Jun 2008 10:32:22 +0800

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 ```Hi Andrew Maybe following paper and included references will be useful for you: Paul D., Skrzypek G., Forizs I, 2007, Normalization of measured stable isotope composition to isotope reference scale -- a review, Rapid Commun. Mass Spectrom 21: 3006-3014. A discussion and mathematical formulation of several existing routinely used "normalization procedures" is presented; the final conclusion is not a surprise but you have all equations in one place. best regards Greg ------------------------------------------------------------- Dr Grzegorz Skrzypek, Research Fellow West Australian Biogeochemistry Centre John de Laeter Centre of Mass Spectrometry School of Plant Biology, The University of Western Australia 35 Stirling Highway (MO90), Crawley WA 6009, Australia Phone Office: +61 8 64883445 Fax +61 8 64887925, email: [log in to unmask] Andrew Schauer wrote: > 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 > [log in to unmask] > > ```