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Issue 11, 2007
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Accurate determination of 234U/238U and 230Th/232Th for U–Th disequilibria studies by MC-ICP-MS with simple bracketing

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Abstract

Accurate determination methods for 234U/238U and 230Th/232Th using multiple collector (MC) ICP-MS with a single secondary electron multiplier through a retarding potential quadrupole filter (RPQ-SEM) have been developed. The RPQ-SEM yield and the instrumental mass discrimination were simultaneously corrected by the simple bracketing method which utilizes accurately determined standard solutions measured by TIMS. For the bracketing and as an evaluation of the precision of the method, four standard solutions, NBL-145 U and U-m for U, and Th-I and Th-II for Th, were prepared, and NBL-145 U and Th-I were used as bracketing standards. The U and Th amounts of 0.5–21 ng and 0.6–21 ng used in U-m and Th-II analyses gave intermediate precisions (2RSD) of 0.85–0.06 and 0.88–0.19%, respectively, and vary from TIMS measurements by <0.35 and <1.1%, respectively, which agrees with error values in TIMS analyses. To achieve similar intermediate precisions of 0.2 and 0.6% (2RSD) in the U and Th isotope analyses to that of TIMS, 3 and 2 ng of U and Th are sufficient. When only the isotope analysis is performed, the required amounts of U and Th can be reduced by half. The precision of the isotope analyses, as well as the concentration determinations, were further confirmed by analyses of U and Th separated from the GSJ standard basalt, JB-2.

Graphical abstract: Accurate determination of 234U/238U and 230Th/232Th for U–Th disequilibria studies by MC-ICP-MS with simple bracketing

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Article information


Submitted
09 May 2007
Accepted
20 Jun 2007
First published
13 Jul 2007

J. Anal. At. Spectrom., 2007,22, 1383-1389
Article type
Paper

Accurate determination of 234U/238U and 230Th/232Th for U–Th disequilibria studies by MC-ICP-MS with simple bracketing

A. Makishima, T. A. Chekol and E. Nakamura, J. Anal. At. Spectrom., 2007, 22, 1383
DOI: 10.1039/B706907C

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