Absolute Isotopic Abundance and the Atomic Weight of a Reference Sample of Thallium.
Absolute Isotopic Abundance and the Atomic Weight of a Reference Sample of Thallium.
复制标题
铊参考样品的绝对同位素丰度和原子量。
DOI：
10.6028/jres.085.001
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发表时间：
1980
影响因子：
--
通讯作者：
W. C. Purdy
中科院分区：
文献类型：
--
作者：
L. P. Dunstan;J. W. Gramlich;I. L. Barnes;W. C. Purdy
自1962年以来，铊的原子量一直保持在204.37 ± 0.03。然而，在这种不确定性水平下，原子量成为高精度分析的限制因素。铊原子量的新质谱测定已经完成。开发了一种高精度的分析技术，使得可以将精确已知量的203 Tl和205 Tl分离的同位素混合以产生用于校准质谱仪的标准。这种分析技术包括重量法测定99.3%的0020铊作为Tl 2CrO 4。然后将可溶性铊等分并通过同位素稀释质谱法测定。在制备最终溶液（从其中取出测定和校准样品）之前，通过溶剂萃取和电沉积纯化分离的同位素。本文介绍了一种钨丝表面电离技术，用于铊同位素丰度的精确测量。该技术允许对分离的同位素、校准标准和天然铊参考标准进行同位素分析，精确度优于0.1%。参考样品的205 Tl/2 Tl绝对同位素丰度比为2.38714 ± 0.00101，原子量为204.38333 ± 0.00018。
The accepted atomic weight of thallium has remained at a value of 204.37 ± 0.03 since 1962. At this level of uncertainty, however, the atomic weight becomes a limiting factor to high accuracy analysis. The new mass spectrometric determination of the atomic weight of thallium has been completed. A high precision assay technique was developed so that accurately known quantities of the 203Tl and 205Tl separated isotopes could be mixed to produce standards for calibration of the mass spectrometer. This assay technique involved the gravimetric determination of 99.3 percent of the0020thallium as Tl2CrO4. The soluble thallium was then aliquoted and determined by isotope dilution mass spectrometry. Before making up the final solutions from which the assay and calibration samples would be withdrawn, the separated isotopes were purified by solvent extraction and electrodeposition. A tungsten filament surface ionization technique was developed for the determination of precise isotopic abundance measurements for thallium. This technique allowed isotopic analysis of the separated isotopes, calibration standards, and a natural thallium reference standard with precisions of better than 0.1 percent. The 205Tl/2Tl absolute isotopic abundance ratio of the reference sample was found to be 2.38714 ± 0.00101, yielding an atomic weight of 204.38333 + 0.00018.