A simple-rapid method to separate uranium, thorium, and protactinium for U-series age-dating of materials

• We describe a new method to separate Th, Pa, and U, for age-dating by alpha spectrometry or mass spectrometry.
• The approach enables the analysis of Pa, Th, and U in a single aliquot.
• The procedure can be performed in <3 h and results in less than 50 mL of acid waste.
• The method provides excellent radiochemical yields with virtually 100% radiochemical purity.

Uranium-series dating techniques require the isolation of radionuclides in high yields and in fractions free of impurities. Within this context, we describe a novel-rapid method for the separation and purification of U, Th, and Pa. The method takes advantage of differences in the chemistry of U, Th, and Pa, utilizing a commercially-available extraction chromatographic resin (TEVA) and standard reagents. The elution behavior of U, Th, and Pa were optimized using liquid scintillation counting techniques and fractional purity was evaluated by alpha-spectrometry. The overall method was further assessed by isotope dilution alpha-spectrometry for the preliminary age determination of an ancient carbonate sample obtained from the Lake Bonneville site in western Utah (United States). Preliminary evaluations of the method produced elemental purity of greater than 99.99% and radiochemical recoveries exceeding 90% for U and Th and 85% for Pa. Excellent purity and yields (76% for U, 96% for Th and 55% for Pa) were also obtained for the analysis of the carbonate samples and the preliminary Pa and Th ages of about 39,000 years before present are consistent with 14C-derived age of the material.

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