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Preparation of two isotopic reference materials of thorium gas been performed starting from highly enriched (232)Th (99.99%) and (230)Th (99.8%). After full characterization (chemical and isotopic) of these purified base materials the thorium nitrate was transformed to thorium dioxide. Accurately weighed amounts of the two isotopes in the dioxide form were subsequently dissolved in nitric acid and resulted in solutions with amount ratios n of (230)Th to n of (232)Th close to IE-5 (IRMM-035) and 3E-6 (IRMM-036). These gravimetrically prepared ratios were finally verified by means of thermal ionization mass spectroscopy (TIMS). The purpose of the reference materials is to calibrate thorium isotope amount ratio measurements.

Additional information

Authors: RAPTIS K, JRC Geel (BE);HENDRICKX F, JRC Geel (BE);DE BIÈVRE P, JRC Geel (BE);MAYER K, JRC Karlsruhe (DE)
Bibliographic Reference: Article: Fresenius Journal of Analytical Chemistry (1997)
Record Number: 199711043 / Last updated on: 1997-09-16
Original language: en
Available languages: en