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

In isotope mass spectrometry the atomic weight of an element and its uncertainty is determined by abundance ratio measurements or is calculated from isotope abundances and their uncertainties. The calculation of the atomic weight and its uncertainty from either abundance or abundance ratio data is described applying classical error propagation laws and matrix calculation methods. Procedures which are recommended by the International Union for Pure and Applied Chemistry (IUPAC) are discussed 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 which take into consideration these correlations as well as the uncertainties of the atomic masses and are generally applicable to all multi-isotope systems.