Relative isotope-ratio difference

IUPAC RECOMMENDATIONS 2013
Relative isotope-ratio difference , δ
delta notation isotope delta relative difference of isotope ratios Measure of an isotope ratio in a sample of interest relative to a reference defined by the relation δ = (Rsample - Rstandard)/Rstandard where R is the isotope ratio of the element. Note 1: The reference is often an international measurement standard. Note 2: The same relative differences are used to calculate delta values from the abundance of isotopomers and isotopologs, ion currents, frequencies, or optical extinctions. Note 3: Relative isotope ratio differences are usually small and are therefore often expressed in units of parts per mil with symbol . Note 4: Units of parts per thousand (ppt, 10-3) or parts per million (ppm, 10-6) are deprecated (IUPAC Green Book).
Related Term(s):
Reference(s): T. B. Coplen. Rapid Commun. Mass Spectrom. 25, 2538 (2011). W. A. Brand, S. S. Assonov, T. B. Coplen. Pure Appl. Chem. 82, 1719 (2010).
From Definitions of Terms Relating to Mass Spectrometry (IUPAC Recommendations 2013); DOI: 10.1351/PAC-REC-06-04-06 © IUPAC 2013.
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