Long term dataset of Eu isotope ratio of NIST3117a Eu standard solution determined via multi-collector inductively coupled plasma mass spectrometry during 2017-2024.

This article provides an update to a previously published data article and associated data set regarding Eu isotope ratio of NIST3117a Eu chemical solution, determined over the period 2017-2024. The Eu isotope ratios were measured via MC-ICP-MS using various Sm isotope pairs -147Sm-149Sm, 147Sm-154Sm, 149Sm-154Sm and 150Sm-154Sm-based on the exponential law over the eight-year period. Measurements were conducted under both wet plasma conditions (using spray chamber) and dry plasma conditions (using Aridus II system). The mean δ¹⁵³Eu values for all Sm isotope pairs are close to 0 ‰, and their 2SD intervals include zero, indicating no systematic bias from the choice of Sm pair or the sample-introduction system. While the precision of δ¹⁵³Eu values for NIST 3117a varies slightly among different Sm isotope pairs, it remains generally consistent. These results demonstrate that Sm-based internal normalization yields robust and reproducible Eu isotope ratios by MC-ICP-MS. The dataset can serve as reference for studying Eu isotope fractionation in geological rocks and meteorites. 36 • No measurable bias in the Eu isotopic composition of the NIST 3117a standard solution is observed with respect to the selection of Sm isotope pairs for normalization or the sample introduction technique.