Relative isotope-ratio difference: Difference between revisions

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Relative isotope-ratio difference , δ
IUPAC RECOMMENDATIONS 2013
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 = (R_sample - R_standard)/R_standard 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.
Index of Recommended Terms

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 Measure of an isotope ratio in a sample of interest relative to a reference defined by the relation
-::&delta; = (R<sub>sample</sub>  R<sub>standard</sub>)/R<sub>standard</sub> where R is the isotope ratio of the element.
+::&delta; = (R<sub>sample</sub> - R<sub>standard</sub>)/R<sub>standard</sub> 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 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<sup>3</sup>) or parts per million (ppm, 10<sup>6</sup>) are deprecated (IUPAC [[Green Book]]).
+:''Note 4'': Units of parts per thousand (ppt, 10<sup>-3</sup>) or parts per million (ppm, 10<sup>-6</sup>) are deprecated (IUPAC [[Green Book]]).
 |rel=
 |ref=T. B. Coplen. Rapid Commun. Mass Spectrom. 25, 2538 (2011).