High-precision determination of {sup 234}U/{sup 238}U activity ratios in natural waters and carbonates by ICPMS
- John Carroll Univ., University Heights, OH (United States). Dept. of Chemistry
- Case Western Reserve Univ., Cleveland, OH (United States). Dept. of Geological Sciences
A method has been developed for precise measurement of {sup 234}U/{sup 238}U activity ratios in natural waters and carbonates using quadrupole inductively coupled plasma mass spectrometry. A recovery of 80--85% of seawater U is achieved by Fe(III) coprecipitation followed by extraction chromatography with a supported dipentyl pentane phosphonate material; 90--95% of U is recovered from carbonates, which are dissolved in HNO{sub 3} and subjected to the same extraction chromatographic preparation. Isotopic measurements are made via recirculating pneumatic nebulization of small volumes of solutions containing 0.5--5 mg/L U. {sup 234}U/{sup 235}U is measured as a proxy for determination of {sup 234}U/{sup 238}U; iridium is added to sample solutions and the ion ratio {sup 191}Ir{sup 40}Ar{sup +}/{sup 193}Ir{sup 40}Ar{sup +} is measured for internal mass discrimination correction {sup 234}U/{sup 238}U activity ratios in the range 1.143--1.154 are observed for 13 seawater and contemporary corals, in agreement with the established marine {sup 234}U/{sup 238}U activity ratio. For samples sizes of 5--25 {micro}g U, ICPMS uncertainties of {+-} 0.2--0.5% relative, 2{theta} standard error, approach those obtained for < 0.1 {micro}g U by thermal ionization mass spectrometry. Measurements of {sup 234}U/{sup 238}U activity ratios in bottled waters, Lake Erie surface waters, mollusk fossils, and fertilizers are also demonstrated.
- OSTI ID:
- 338631
- Report Number(s):
- CONF-980310--
- Country of Publication:
- United States
- Language:
- English
Similar Records
({sup 234}U/{sup 238}U) activity ratios in freshwaters as tracers of hydrological processes: The Strengbach watershed (Vosges, France)
Precise measurements of /sup 234/U//sup 238/U and U concentrations in profiles of Pacific and Atlantic waters