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Inorganic Chemistry Division


Number: 2002-049-2-200

Title: A new comprehensive report on the isotopic compositions of the elements for global user communities

Task Group Chairman: Robert D. Loss

Members: Michael Berglund, John Karl Böhlke, Tyler B. Coplen, Tiping P. Ding, Paul De Bièvre, John R. De Laeter, Mitsuru Ebihara, A. M. Fouillac, Klaus G. Heumann, Norman E. Holden, Hiroshi Hidaka, Kevin J.R. Rosman, Etienne Roth, Philip D.P. Taylor, Thomas Walczyk, Ying-Kai Xiao, Shigekazu Yoneda, and Michael Wieser

Completion Date: 2007 - project completed

To design, compile and produce a new comprehensive Report on the Isotopic Compositions of the Elements, containing updated data and in a format suitable for the 21st Century.

In the past, CAWIA has produced several tables of the isotopic compositions of the elements (e.g. the most recent published in 1997) with isotopic data representing the best available measurements and representative materials. The aim of this project is to update and drastically upgrade this information, which has not been done in 7 years. Apart from the upgrading (incorporating new information obtained since 1997), the data handling procedures for the future table should also be modified to achieve recommended isotopic compositions that are fully in line with standard atomic weights. This is not always the case today.

With increasing importance of isotope ratio measurements in chemistry, environmental sciences, product authentication, forensic and life sciences, there is a need for an expanded and revised database on isotopic abundances in normal terrestrial materials and associated reference materials with standard atomic weights that reflect the current knowledge of isotopic compositions. This represents a major modification and an expansion of the present isotopic composition compilations. It will include a computer database accessible by the chemical community and will facilitate future updates, as new information becomes available.

Project phase 1: A special core task group consisting of R. Loss, J.K. Böhlke, K. Rosman, T. Coplen, T. Walczyk, M. Berglund, P. Taylor will hold a 3-day workshop August 5, 6, and 7 in Ottawa to develop guidelines for the new RICE data tables for use by the Subcommittee for Isotope Abundance Measurements (SIAM) when reviewing currently tabulated and subsequently reported isotopic compositions. On August 8 and 9 in Ottawa (IUPAC GA 2003), a forum of the full Task Group will meet to discuss the role of the new comprehensive "Report on the Isotopic Compositions of the Elements" for global user communities within the future structure of IUPAC, its Divisions, Subcommittees, and Commissions. A face-to-face meeting is critical, as it is the most cost effective way to engineer this novel system via in depth discussions with the relevant experts in a timely manner, which is important to this rapidly changing scientific subject. The Commission's collective experience over the past decades is that this is only viable approach, in view of the number of issues involved and the fact that experts from different scientific disciplines are needed. A new layout for the table of isotopic compositions will be drafted.

Project phase 2: By electronic communication, the core task group will further revise and then finalise these Guidelines and make a template for the novel table.

A novel calculation tool is available and will be distributed by IRMM for free to the project members. This software estimates the uncertainty of the isotope abundances from isotope ratios (and vice versa). It takes into account natural isotopic variation (e.g., from the IUPAC SNIF report), and it allows ratio conversion. It also allows the user to produce a standard atomic weight for the element. The intention is to have a hard link between the reservoir of raw literature data stored and the end products delivered. This will drastically improve archiving and it will allow for a more efficient review of previous decisions made by the Commission.

(last update 29 Jan 2007)
The task group reviewed key uncertainty inputs and developed prototype uncertainty determinations suitable for Isotopic Composition (re)determination of published data utilizing the analysis and computational rules of the 'ISO guide to the expression of uncertainty in measurement' as used by the European cooperation for Accreditation of Laboratories. These procedures were used to prepared evaluated Isotopic Composition and Atomic Weight data for nickel, sulfur, and osmium. Unfortunately, the prototyping rapidly revealed a myriad of unforeseen complexities and difficulties required to complete this for all the polyisotopic elements.

Due to user-community demand, the task group recommended reporting evaluated isotope ratios, as well as isotopic abundances, which is a major departure from previous reporting of only isotopic abundances. This created major difficulties in evaluating and (re)determining isotope-ratio uncertainties from those publications that only reported abundances, especially those with unclear, non-standard, or even non-existent uncertainties.

The amount of time required to review the substantial literature and evaluate isotope data for all of the proposed parameters was much greater than first thought. In particular, the degree of interpersonal interaction involved in evaluating the data clearly could not be met within the proposed project time lines.

Recognizing the complications and difficulties involved in the full re-evaluation of all polyisotopic elements, the task group recommended a new project #2003-031-2-200 'Isotopic Compositions of Selected Elements'. Funded in 2004, that project has made substantial progress.

The new evaluation templates and experience gained by the task force members in these two projects have been applied by the Commission on Isotopic Abundances and Atomic Weights at the 43rd IUPAC General Assembly in Beijing 2005 and resulted in fully revised atomic weight data for 12 elements. (Pure Appl. Chem. 78(11), 2051-2066, 2006)

project completed

Last Update: 6 February 2007

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Page last modified 6 February 2007.
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