Journal article
Uranium and thorium isotopic and concentration measurements by magnetic sector inductively coupled plasma mass spectrometry
Chemical geology, Vol.185(3), pp.165-178
2002
DOI: 10.1016/S0009-2541(01)00404-1
Abstract
We have developed techniques by sector-field inductively coupled plasma mass spectrometry (ICP-MS) for measuring the isotopic composition and concentration of uranium and thorium, focusing on the rare isotopes,
230Th and
234U. These isotopes have been widely used as tracers in earth sciences, e.g., chronology, paleoclimatology, archeology, hydrology, geochemistry, and oceanography. Measurements made on reference materials demonstrate that the analytical precision approximates counting statistics and that the accuracy of the measurement is within error of accepted values. Routine measurement times are 20 min for U and 10 min for Th. The sensitivities (ions counted/atoms introduced) are 2–3‰ for U and 1.5–2‰ for Th. Samples of 10–40 ng of
238U (0.5–2.0 pg of
234U) give measurement precisions of 1–2‰ (2
σ) for
δ
234U and U concentration ([U]). Only 0.4 pg of
230Th are needed to achieve [
230Th] and
230Th/
232Th data with errors less than 5‰ even for cases where
230Th/
232Th is 10
−5 or less. Our ICP-MS data, including uranium standards, thorium standards,
238U–
234U–
230Th–
232Th dating of speleothems and
230Th–
232Th in oceanic particulates, replicates measurements made by thermal ionization mass spectrometry (TIMS). Compared to TIMS, the ICP-MS method allows smaller sample size and higher sample throughput due to higher sensitivity, fewer sample preparation steps and shorter measurement times. However, mass biases, intensity biases, spectral interferences and instrumental blanks are significant and must be addressed.
Details
- Title: Subtitle
- Uranium and thorium isotopic and concentration measurements by magnetic sector inductively coupled plasma mass spectrometry
- Creators
- Chuan-Chou Shen - National Cheng Kung UniversityR. Lawrence Edwards - University of MinnesotaHai Cheng - University of MinnesotaJeffrey A Dorale - University of MissouriRebecca B Thomas - University of MinnesotaS Bradley Moran - University of Rhode IslandSarah E Weinstein - University of Rhode IslandHenrietta N Edmonds - The University of Texas at Austin
- Resource Type
- Journal article
- Publication Details
- Chemical geology, Vol.185(3), pp.165-178
- Publisher
- Elsevier B.V
- DOI
- 10.1016/S0009-2541(01)00404-1
- ISSN
- 0009-2541
- eISSN
- 1872-6836
- Language
- English
- Date published
- 2002
- Academic Unit
- Earth and Environmental Sciences
- Record Identifier
- 9984229165402771
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