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van Calsteren, Peter and Thomas, Louise
(2012).
DOI: https://doi.org/10.1039/C2JA30026E
Abstract
Quantitation of protactinium, 231Pa in abyssal carbonates at ~10–12 g g–1 levels, presents certain challenges because it is the only isotope of this element that is present in the natural environment and its half-life of 32 800 y is too long for useful measurement using alpha-particle or gamma-ray spectroscopy. However, because it is an isotope in the 235U decay chain, closely linked to the 238U decay chain, quantitation can be achieved relative to a carbonate standard in secular radioactive equilibrium. The 238U, 235U, 234U, 230Th and 232Th isotopes in the carbonate standard are determined with a mixed 236U-229Th spike using isotope dilution protocols and a Multi-Collector Inductively Coupled Plasma Mass Spectrometer.