Project Details Assessment of Stable Isotopic Reference Materials

Project No.:
Start Date:
01 August 2014
End Date:


Isotopic abundance ratio variations of the elements are used in many scientific applications. They can identify the origin of samples or past chemical processes. The many commercial and scientific applications, e.g. in food traceability or as natural tracer, require efforts to ensure worldwide data comparability by use of suitable reference materials. While the light elements have been studied using the delta notation for more than sixty years, the heavier elements are now joining this convenient and more accurate way of expressing results, mainly (but not exclusively) owing to the invention of High Resolution ICP-MS. Direct comparison of samples with reference materials ensure best results, guided by the principle of identical treatment, requiring a far reaching chemical compatibility of analyzed materials. This requirement has generated the need for a large number of reference materials, which must be well calibrated against each other.

A predecessor project (project 2009-029-1-200) had been started at the CIAAW meeting in 2009 and resulted in an extensive publication with a comprehensive list of reference materials for delta type measurements of various elements. The main objective of this new project is to extend the list of elements covered by careful evaluation of studies of the isotopic composition of more elements, to update already existing information by screening new publications for revised and additional reference values, and to help to identify any gaps for available reference materials. Hence, this project and its updated list will assist the scientific community in achieving internationally comparable results.


Isotopic abundance variations measured as delta-values are used increasingly in various scientific disciplines and applied in industry or commerce e.g. to demonstrate authenticity of goods or fraudulent adulteration of raw products. Therefore, an increasing number of reference materials is needed to ensure the required quality of day-to-day calibrations and to guarantee the requested accuracy of analytical measurements. Moreover, new matrix matched materials are needed and provided to encompass the increasing variety of investigated samples and preparation techniques. Additional isotopic systems have been added to the scientific treasure chest of isotopes and the use of delta notations has been adapted for these higher atomic weight elements.

All these considerations underline the indispensible need to provide a properly recorded and evaluated reference data collection for use by laboratories worldwide. It is a prerequisite that these reported values are reviewed for their metrological characteristics to ensure that only data fulfilling the highest level of quality are finally taken into account.

Therefore, CIAAW will assemble a number of experienced specialists with the required expertise in high precision isotope abundance ratio measurements and metrology. This group of experts shall assess data and decide on reference values in close cooperation with the IAEA, NIST, USGS, IRMM, BAM, NIM and NRC as the main distributing agencies of reference materials. This cooperation is believed to boost the applicability of existing reference materials, to identify needed materials and to trigger the production of new reference materials in order to bridge the existing gaps.

This project has the potential to harmonize measurement results and thus foster worldwide data comparability based on control of the integrity of internationally accepted reference values, and to remove existing discrepancies on recommended values as suggested by different organisations or researchers. The tables in the previous report comprising recommended values for available reference materials will be used as an initial point and will be comprehensively updated with new data as well as for new materials and additional isotopic systems. This database will be provided using a web-based platform (e.g. on the web page of the Commission on Isotopic Abundance and Atomic Weights) as well as in the new publication.


Sep 2017 update – In the initial part of the project an intense screening of new literature on isotope reference materials was performed. Since the publication of the IUPAC Technical Report “Assessment of international reference materials for isotope-ratio analysis” of W. Brand et al. (PAC 86(3), pp. 425-467, 2014; to date it resulted in altogether 56 new publications citing new reference materials or publishing upgrading isotopic values covering altogether 31 elements. In this collection over ten elements are included which so far were not covered in the first Technical Report (Ba, Eu, Hf, Ir, Nd, Sb, Sn, Ti, V, W, Yb). Criteria for inclusion or exclusion of proposed new reference materials are suggested. The original anticipated time frame of the project was not sufficient to include several expected key publications covering reference materials for several elements (e.g. hydrogen, carbon).

Now as next step the collected publications will be assigned to individual project members for updating the existing information by element and drafting the new report contents. This phase is expected to be concluded in 2018. Further publications may still be added during that period. Work in this phase will also include the cross check for existing reference materials of existing publications with updated information. In 2019 after a final check by the project members, the new report will be submitted for publication as update of the Brand et al. Technical Report.

Page last updated 19 Sep 2017