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Inorganic Chemistry Division (II)


Number: 2003-033-1-200

Title: Determination of atomic weights using new analytical techniques

Task Group
Michael Wieser

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

New analytical techniques, including inductively coupled plasma-mass spectrometry, have recently provided atomic weights with unparalleled precision. The purpose of this project is to assess the uncertainties in these new methods in atomic-weights work, evaluate published work, and, if possible, make recommendations to update IUPAC's Table of Standard Atomic Weights.

New analytical techniques, including inductively coupled plasma-mass spectrometry (ICP-MS), have recently provided atomic weights of chemical elements with unparalleled precision. For example, ICP-MS analyses on boron reference materials distributed by the International Atomic Energy Agency have very low uncertainties in their atomic weights, but the values do not agree well with previous thermal ionization mass spectrometric (TIMS) measurements. In fact, ICP-MS values from different laboratories do not overlap even with 2-s uncertainties. The reasons for the lack of agreement currently are not well understood. The purpose of this project is to assess the uncertainties of these new methods in atomic-weights work.

Meetings are planned in 2004, 2005, 2006, and 2007. Based on information gained at the 2004 Goldschmidt Conference in Copenhagen, strategies will be developed to allow the task group to compare uncertainties of atomic-weight measurements made by TIMS, ICP-MS, and other methods. In order to increase the knowledge base of the task group in ICP-MS studies, individuals with ICP-MS experience will be identified in Copenhagen and asked to join it.

As was learned in early August at a meeting in Ottawa, comparing data from TIMS and ICP-MS methods is difficult. One possibility is for task group members to develop algorithms for comparing atomic weight uncertainties determined by TIMS, ICP-MS, and other new methods. These algorithms will be applied to published atomic-weights literature and the results will be presented to IUPAC's Commission on Isotopic Abundances and Atomic Weights in Turin during the General Assembly (2007). If the development of these new algorithms is successful, they will provide data for the basis of a new Table of Standard Atomic Weights, which could be submitted to PAC as a publication titled "Atomic Weights of the Elements 2007."


Last update: 15 April 2004


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