Isotopic Compositions of the Elements 2009 (IUPAC Technical Report) (Report‪)‬

INTRODUCTION The Commission on Isotopic Abundances and Atomic Weights (CIAAW) of the International Union of Pure and Applied Chemistry (IUPAC) has provided regular assessments of the standard atomic weights and isotopic compositions of the elements [1]. CIAAW has evaluated the isotopic composition of each element by examining carefully the most accurate and precise isotope-abundance measurements of the element in selected samples through its Subcommittee for Isotopic Abundance Measurements (SIAM), and by compiling evidence for known variations in the isotope abundances of the element in normal terrestrial materials, through its Subcommittee on Natural Isotopic Fractionation (SNIF). By "normal", CIAAW refers to terrestrial occurrences that satisfy the following criterion: