Application of retardation filters has revolutionized the use of multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) for the measurement of U-series disequilibria. Here, we present an evaluation of the application of retardation energy filters coupled with ion counting detectors for the measurement of U-series disequilibria by MC-ICPMS. We show that: 1) The RPQ minimizes backgrounds caused by ions experiencing irregular flight paths at high masses of uranium series nuclides. This reduced background is important for low count rate measurements and has enabled us to develop an improved method for the determination of 226Ra/228Ra ratios using a dual SEM/RPQ collector block. 2) Systematic biases exist for isotope ratios of 234U/238U and 230Th/232Th without the use of RPQs; thus, the RPQ is important for measurement of both of these isotope ratios. 3) That the RPQ makes possible 210Pb measurements in geologic samples using MC-ICPMS, but that this application is limited to samples that have low common Pb, such as carbonates and silica sinter. Additionally, we present mass spectrometric and gamma counting data for U-Th-Ra disequilibria in rock standard reference materials including AGV-2, AThO, BCR-1, BCR-2, BHVO-2, BIR-1a, DTS-1, PCC-1, RGM-2, TML, and W-2a. Comparing this new data with values from published literature enables us to provide consensus or recommended values for U, Th, and 226Ra concentrations and 230Th/232Th ratios for each of these standards. We note that this is the first compilation of recommended radium concentrations for rock standard reference materials.
Bibliographical noteFunding Information:
Development of U-series measurements by ICP-MS (both single collector and multi collector) began at the Woods Hole Oceanographic Institute and has continued at the University of Wyoming. As such, this work has been supported by numerous grants over many years, including but not limited to National Science Foundation grants EAR 0960270 , EAR 1447750 , EAR 1049950 , OCE 1060434 , OCE 060383800 , OCE 0079733 , OCE 9730967 awarded to KWWS and collaborators. Funding for field work to collect silica sinter samples was provided by the Roy J. Shlemon Center for Quaternary Research.
- Abundance sensitivity
- Retarding potential quadrupole