Stable Isotope EasyIsoCalculator

The stable HCNOS isotope compositions can be reported as:

1) the isotope ratio of two stable isotopes (R);

2) isotope delta value (δ); and

3) atom fraction of the isotopes (x).

 

Recalculations between these different expressions are needed frequently and require the use of the absolute isotope ratio for the zero points of the stable isotope delta scales (Rstd). The inconsistent use of Rstd values may lead to a discrepancy in recalculated results.

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We summarised the recalculation procedures between different expressions of the stable isotope compositions and introduced a user-friendly EasyIsoCalculator that allows recalculation between the main expressions of isotope compositions.

 

We mathematically and empirically evaluated the possible inconsistencies in reporting of the stable isotope data due to use of different Rstd and different normalization methods. The recalculation between δ-values and other expressions of the stable isotope compositions always involves the use of Rstd. Differences in the selection of Rstd value may lead to significant differences between different laboratories. Consistent use of the same Rstd values is required to eliminate the unnecessary discrepancy if different data sets are recalculated from delta value to other expressions.

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Grzegorz Skrzypek and Philip Dunn

Grzegorz.Skrzypek@uwa.edu.au

Philip.Dunn@lgcgroup.com

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Please cite this software as follow:

Skrzypek G., Dunn P., 2020. The recalculation of the stable isotope expressions for HCNOS – EasyIsoCalculator. Rapid Communications in Mass Spectrometry 34: e8892.

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Skrzypek G., Dunn P. 2020. Absolute isotope ratios defining isotope scales used in isotope ratio mass spectrometers and optical isotope instruments. Rapid Communications in Mass Spectrometry 34: e8890.