Evaluation of a new generation quadrupole-based ICP-MS for uranium isotopic measurements in environmental samples

We compare the analytical performance of a modern quadrupole-based ICP-MS ('X-Series', Thermo-Electron, Winsford, UK) with a singlecollector double-focusing sector-field ICP-MS ('Axiom', VG Elemental, Winsford, UK) for uranium isotopic measurements in environmental samples. We focus on the precision and accuracy obtained with both instruments for the 235U/238U isotopic ratios and on the abundance sensitivity that is a key parameter for low 236U/238U isotopic ratios measurements. We observe that isotopic measurements are more precise accurate with the 'X-Series' than with the 'Axiom'. Besides, we demonstrate that the 'Axiom's' higher abundance sensitivity limits its capability to measure 236U/238U ratio below a few ppm. (author)