Project Details Evaluated Published Isotope Ratio Data (2013-2018)

Project No.:
Start Date:
24 May 2017
End Date:


Evaluate isotope ratio publications between 2013 and 2018 to determine isotope ratio measurements that should be part of the CIAAW database and influence the standard atomic weights. This project will also seek to backfill many missing historical entries and modernize the data evaluation methods by the CIAAW. The means to modernize the current data evaluation practices of the CIAAW were discussed during the 2015 IUPAC-SIAM meeting and outlined recently by Meija and Possolo (Metrologia 2017, 54, 229-238;


The aim of the task group selected by the CIAAW, is to evaluate new isotope ratio publications from 2013. The evaluated data will be incorporated into the CIAAW Table of Standard Atomic Weights and possibly change the entries of current standard atomic weights. Thus, the standard atomic weights will follow the recent developments and findings in science.

The project will also seek to establish a transparent and modern data analysis framework for isotope ratio evaluation (as outlined by Meija and Possolo, Metrologia 2017, 54, 229-238). Particular attention will be paid to increase the transparency of the algorithms used and backfilling the CIAAW database with the relevant historical data.

In July 2019, Task Group members will convene in Paris, during the IUPAC General Assembly, to present their findings to the Commission on Isotopic Abundances and Atomic Weights in a face-to-face meeting.

Prior to the face-to-face meeting in Paris 2019, detailed discussions and calculations will be carried out on any chemical element for which new isotope ratio information exists. Particular attention will be paid to authors’ evaluations of uncertainty, the quality of the performed measurements, the selection of materials for analysis, and the variability of isotope ratio measurements in these materials.

It is anticipated that new standard atomic weights will be recommended. Subsequently, a publication titled “Atomic Weights of the Elements 20XX” will be prepared for Pure and Applied Chemistry.


Aug 2021 update – In July 2021, Task Group members convened virtually to evaluate literature on recent isotope ratio measurements. This included reports for 16 chemical elements and it is anticipated that these assessments will be incorporated into the upcoming Table of Isotopic Composition of the Elements.

May 2022 update – The “Standard atomic weights of the elements 2021 (IUPAC Technical Report)” has been published as Pure and Applied Chemistry, 2022, AOP 4 May 2022;

Page last updated 9 May 2022