INORGANIC
CHEMISTRY DIVISION
COMMISSION ON ATOMIC WEIGHTS AND ISOTOPIC ABUNDANCES
SUBCOMMITTEE ON NATURAL ISOTOPIC FRACTIONATION
Isotope-abundance variations of selected
elements (IUPAC Technical Report)
T.B. Coplen,*
J.K. Bohlke, P. De Bievre, T. Ding, N.E. Holden, J.A. Hopple, H.R. Krouse,
A. Lamberty, H.S. Peiser, K. Revesz, S.E. Rieder, K.J.R. Rosman, E.
Roth, P.D.P. Taylor, R.D. Vocke, Jr., and Y.K. Xiao
Abstract: Documented variations in the isotopic compositions
of some chemical elements are responsible for expanded uncertainties
in the standard atomic weights published by the Commission on Atomic
Weights and Isotopic Abundances of the International Union of Pure and
Applied Chemistry. This report summarizes reported variations in the
isotopic compositions of 20 elements that are due to physical and chemical
fractionation processes (not due to radioactive decay) and their effects
on the standard atomic-weight uncertainties. For 11 of those elements
(hydrogen, lithium, boron, carbon, nitrogen, oxygen, silicon, sulfur,
chlorine, copper, and selenium), standard atomic-weight uncertainties
have been assigned values that are substantially larger than analytical
uncertainties because of common isotope-abundance variations in materials
of natural terrestrial origin. For 2 elements (chromium and thallium),
recently reported isotope-abundance variations potentially are large
enough to result in future expansion of their atomic-weight uncertainties.
For 7 elements (magnesium, calcium, iron, zinc, molybdenum, palladium,
and tellurium), documented isotope variations in materials of natural
ter- restrial origin are too small to have a significant effect on their
standard atomic-weight uncertainties. This compilation indicates the
extent to which the atomic weight of an element in a given material
may differ from the standard atomic weight of the element. For most
elements given above, data are graphically illustrated by a diagram
in which the materials are specified in the ordinate and the compositional
ranges are plotted along the abscissa in scales of (1) atomic weight,
(2) mole fraction of a selected isotope, and (3) delta value of a selected
isotope ratio.
* Corresponding author.
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