Determination of uranium isotope ratios by multi-static MIC-ICP-MS: method and implementation for precise U- and Th-series isotope measurements
Abstract
In order to improve and extend the application of U- and Th-series isotope measurements a new technique for MIC-ICP-MS (multiple ion counting 84 ± 0.000
87)
× 10−5 or a δ234U value of −36.96 ± 0.16, respectively, was determined for CRM-145 in good agreement with reference data. Based on the precisely determined U isotope ratios we furthermore developed a combined multi-static U- and Th-measurement method. This approach extends this new MIC-ICP-MS technique to those U- and Th-series isotope systems having no constant isotope ratio for normalization (e.g., 230Th/232Th, 230Th/229Th) and is the key for new approaches to determining 226Ra/228Ra and 231Pa/233Pa. The applicability of the methods presented here is demonstrated by accurate dating of very young corals (10–350 y).