Project Details Isotopic compositions of selected elements

Project No.:
2003-031-2-200
Start Date:
01 January 2004
End Date:
21 September 2009
Division Name:
Inorganic Chemistry Division
Division No.:
200

Objective

To design, compile and produce a new Report on the Isotopic Compositions of selected Elements, containing updated data with uncertainties that conform to ISO 9001 requirements.

Description

The Commission on Isotopic Abundances and Atomic Weights (CIAAW) has produced in the past (last one in 2001) several tables emphasizing the isotopic abundances of the elements. The evaluated data provided on these tables has usually been selected to represent a) the best available measurements and b) that present in representative materials which do not always correspond to the Commission’s recommended standard atomic weights for each element. The inconsistencies between some of the recommended isotopic abundances and atomic weights has been requiring our attention for some time which this proposal aims to correct.

> link to Commission page

The second major aim of this project is to address the increasing importance of isotope ratio measurements in chemistry, geological, environmental sciences, product authentication, forensic and life sciences. This project recognizes the primary source of isotopic data reported in the literature is as ratios and the urgent need for an expanded and revised database listing isotopic ratios and isotopic abundances in normal terrestrial materials and associated reference materials to suit the majority of user communities.

For this reason CIAAW proposes to issue a new authoritative document to update and disseminate this information. This is a major modification and expansion of the present compilations and will include a simple spreadsheet type data base from which a variety of reports can be extracted and to facilitate future updates.

A major requirement of this project is to re-evaluate the uncertainties associated with the original data, which necessitates revisiting all of the original literature, and the development of new data evaluation guidelines. Because of the time required to re-evaluate all elements only a set of elements of immediate interest to the isotope user community will be published in the first instance. In the first set of elements, iron, tin, europium, dysprosium, and erbium will be evaluated.

The task group will
– develop and implement new guidelines for data evaluation and presentation
– review and evaluate the isotope ratio data publications for +AH4-10 selected elements
– prepare a new layout of the spread sheet style data base and sample extracted tables
– issue the new tables and widely distribute it using suitable channels

Progress

August 2007 – The project is a follow on from a previous (RICE1 2002-049-2-200) project. Various members of the task group have attended a series of workshops in IRMM Belgium and the Chinese Academy of Geological Science in Peking to develop a complete and transparent ISO9001 based working protocol for the evaluation of published isotopic compositions of the element according to ISO 9001 requirements. The elements evaluated were Pt, Ta, La, Nd, Zn and Cr.

The protocols and evaluations were recommended to the next Commission on Isotopic Abundances and Atomic weights for approval at the Commission at the PISA 2007 meeting. During this meeting the Commission approved these protocols be trialed for the next (2007-2009) published isotopic composition evaluation period.

A full report describing the details of proposed CIAAW guidelines for determining best measurements of isotopic compositions and representative isotopic compositions, and for calculating atomic weights and full uncertainties is available. The report also illustrates the templates and forms to be used in future evaluations. A spreadsheet/data base system has also been developed to simplify the evaluation process and clearly show calculation paths. The report has been prepared by Michael Berglund, JK Böhlke, and Bob Loss.

The protocols developed in this project enabled the Commission on Isotopic Abundances and Atomic Weights to revise the standard atomic weight of Zn, which is to be published in “Atomic weights of the Elements 2007” prepared for Pure and Applied Chemistry. The evaluations using these protocols showed that revised standard atomic weight values were not yet needed for the elements Pt, Ta, La, Nd, and Cr.

> September 2009 – Project completed – IUPAC Technical report titled ‘Atomic weights of the elements 2007’ is published in Pure Appl. Chem. 2009, doi:10.1351/PAC-REP-09-08-03.