COMPUTATIONAL PROCEDURES FOR THE TREATMENT OF MEASURED OR PUBLISHED ISOTOPE ABUNDANCE DATA

In isotope mass spectrometry the atomic weight of an element and its u ncertainty is determined by abundance ratio measurements or is calcula ted from isotope abundances and their uncertainties. The calculation o f the atomic weight and its uncertainty from either abundance or abund ance ratio data is described applying classical error propagation laws and matrix calculation methods. Procedures which are recommended by t he International Union for Pure and Applied Chemistry (IUPAC) are disc ussed with regard to their built-in restrictions. Taking into account the correlation between abundance data thereby is the key to reliable uncertainty calculations. Procedures are suggested in this article whi ch take into consideration these correlations as well as the uncertain ties of the atomic masses and are generally applicable to all multi-is otope systems.