用于多接收器等离子体质谱测定的铁铜锌同位素标准溶液研制

近十来年铁铜锌同位素研究已经成为热门研究领域,铁铜锌同位素分析方法日趋成熟,但是铁铜锌同位素标准物质却十分匮乏。目前欧盟参考物质及测量研究所(IRMM)有1个铁同位素标准物质和1个锌同位素标准物质,前者售罄,后者价格昂贵;美国国家标准局(NIST)有1个铜同位素标准物质。为了适应我国铁铜锌同位素研究的发展,本文使用铁铜锌元素浓度标准溶液作为备选标准溶液研制了铁铜锌三个同位素标准溶液(CAGS-Fe、CAGS-Cu和CAGS-Zn)。三个备选标准溶液经过F检验均匀性良好;在38个月内δ56Fe、δ57Fe、δ65Cu、δ66Zn和δ68Zn值没有显著性变化,具有良好的稳定性;主要特性值的推荐值及95%置信水平的不确定度为:CAGS-Fe,δ56FeIRMM014(‰)=0.80±0.05,δ57FeIRMM014(‰)=1.20±0.10;CAGS-Cu,δ65CuIRMM976(‰)=0.57±0.06;CAGS-Zn,δ66ZnIRMM3702(‰)=-0.77±0.10,δ68ZnIRMM3702(‰)=-1.55±0.13。本文研制的标准溶液可用于多接收器等离子体质谱仪测定铁铜锌同位素时的仪器校正和质谱分析过程监控,对于不同实验室的测试数据对比具有重要意义。

New Standard Solutions for Measurement of Iron, Copper and Zinc Isotopic Compositions by Multi-collector Inductively Coupled Plasma-Mass Spectrometry

Direct determination of trace silver in all kinds of geological by Graphite furnace atomic absorption spectrometry has been widely used. The samples were dissolved with the acids system. Thiourea and diammonium hydrogen phosphate were usually used as the matrix modifiers. However, the measurement results of silver were interfered by the matrix elements of calcium and magnesium in the sample, and the service life of the graphite tube was reduced, when the method is used to determinate trace silver in carbonate rock samples. In this paper, the samples were dissolved with a four-acid system of HCl-HNO₃-HF-HClO₄.The matrix elements of calcium and magnesium were rapid reaction generated white precipitate separated, at the same time a volatile ammonium salt medium environment was generated, through adding 45.5 g/L ammonium oxalate matrix modifier in nitric acid medium. Then all kinds of influence of matrix elements of calcium and magnesium were eliminate, through significantly improving the ashing temperature and further removing the ammonium salt medium. The method has been verified by the determination of silver in the National Standard Reference Materials, and the relative error of the measured values is less than 10%. The detection limit of the method for silver is 0.010ug/g, and the precision of the method (n=12) is less than 1.0%.