Isotopic information of (calcium)carbonates and hydroxyapatites are widely used in different fields of research in order to study provenance, migration, authenticity and are used to study past records of environmental conditions (e.g. in climate change adaption). The objective of this project is to collect and compile data on the isotopic composition and mass fractions (with a focus on Sr, Pb, B, Ba, Li, Mg) of materials based on calcium carbonates and hydroxy apatites.
This project will evaluate the data with respect to the (metrological) quality of the analytical approach. For the first time, the isotope user community will be provided with metrologically sound values relative to the accepted 0-anchor materials for isotopic delta data in materials. This is of significant importance especially for solid sample analysis (e.g. by Laser ablation multi collector inductively coupled plasma mass spectrometry (LA-MC ICP-MS)). The values are based on internationally published data as well on laboratory results, which will be compiled within the project. International laboratories (with a focus on metrological institutes) will be contacted for providing their according data. The data will be introduced in a database via a web based interface. The evaluation will be based on metrological principles (according to the best practices of CIAAW). Along with the data, uncertainties of measurements will be collected and evaluated. A combined standard uncertainty budget will be calculated and an uncertainty value will be assigned to the recommended isotope values for the corresponding materials. The dataset will be provided to the stakeholders via the CIAAW homepage as well as scientific publications.
Isotopic data of Sr, Pb, B, Ba, Li, Mg of carbonates and hydroxyapatites are increasingly used in various different fields of science in order to e.g. determine provenance, authenticity, migration of modern or ancient humans or animals (teeth, bones, otoliths) or as a historic recorder of environmental conditions (in incrementally grown matter such as shells, otoliths, corals, teeth or sediments). This isotopic data is increasingly assessed by direct solid analysis such as e.g. laser ablation inductively coupled plasma mass spectrometry. Therefore, the scientific community faces an increasing need for matrix matched reference materials since the users are challenged with calibration of their mass spectrometer and require to establish traceability to international standards (SI units).
Currently, no suitable solid certified reference materials exist for the selected elements and their isotopic composition in calcium carbonate and hydroxyapatite materials even though a large number of data on various materials has been published. This impedes scientific progress and comparability between results on a global scale. Therefore, the scientific community has to rely on compiled data from measurements, which have been accomplished with metrological background. A large number of data exists for a number of certified (NIST SRM 1400, NIST SRM 1486, NRC FEBS-1, MACS, etc.), which have only partly or not been compiled, so far. A variety of other materials is widely used throughout the scientific communities and have the potential to act as reference for the own data.
Over the past decade, thermal ionization mass spectrometry (TIMS) and the multiple collector inductively coupled plasma mass spectrometer have enabled the determination of isotopic composition of strontium and other elements with unprecedented levels of precision. Especially B, Li, Mg, Sr, Ba and Pb isotope ratios have been used for decades in different fields of research. Many working groups in geochemistry, the environmental sciences and life sciences are employing isotope abundance data to investigate processes involving these elements. However, the intercomparison of results among research groups is impeded because there are no solid isotopic reference materials. To enable interlaboratory data comparison, a variety of solid materials (including nano pelleted hydroxyapatite and calcium carbonate material) have been analyzed by different laboratories worldwide. Evaluated data will be collected and compiled and then be subject to metrological calculations in order to suggest reliable isotope ratio values expressed as delta value relative to the commonly used certified isotope ratio materials.
Meetings will be organized to discuss and evaluate the collected data and establish measurement protocols along with uncertainty budgets. In addition, laboratories will be invited to generate measurements and/or to provide data on the isotopic composition of reference materials, which have been accomplished in the laboratories and not been published, so far. An open call will encourage these laboratories to provide measurement data via a web-based interface at the CIAAW homepage.
The techniques used for characterization will consider data generated by (LA)-(MC) ICP-MS, TIMS and SIMS (secondary ionization MS). In addition to Sr (and other) isotope ratios, data of commonly available samples (e.g. FEBS-1, JCp-1, MACS 3) will be evaluated for selected mass fractions relevant for the analysis of isotope ratios in the different fields of application (e.g. Sr, Ca, Ba, Mg, B, Li, Pb, U). During the project, all data will be collected and rated by their metrological quality allowing for the establishment of reference values for the selected material. Isotope ratios will be reported as delta values relative to the recommended 0-anchor materials. CIAAW provides the required expertise for this project as responsible group of specialists.
August 2018 update – Project announcement published in Chem Int July 2018, p. 32; https://doi.org/10.1515/ci-2018-0316
Page last updated 6 Aug 2018