高Cr地质样品的Mg同位素分析方法

High Precision Magnesium Isotope Measurement for High-Cr Samples

使用多接收等离子体质谱仪测定Mg同位素比值时,Cr元素会干扰测定结果。高Cr地质样品如铬尖晶石和铬铁矿中的Cr/Mg值可高达5︰1。针对这些样品,本研究检测了Cr对Mg同位素测试的干扰程度,评估了实验室流程中Cr和Mg的分离效果,探讨了Cr在淋洗过程中的行为。实验采用1mol/L HNO_3及2.3mL AG50W-X8型阳离子树脂,仅通过一次分离纯化便能将Mg与Cr等其他基质元素有效分离,且Mg的回收率可达99.8%,测试结果可靠。此外,Cr在分离过程中分为两阶段被洗脱,这与其在样品中不同的赋存价态有关。

High chromium contents of samples will significantly interfere results ofthe Mg isotopic analysis using a multicollector inductively coupled plasma mass spectrometry（ MC-ICP-MS）. There are high-Cr samples,such as chrome spinel and chromite with Cr / Mg ratios up to 5︰1. This study investigates the intensity of interference of Cr on Mg isotopic analyses,evaluates the separation efficiency of Cr from Mg in laboratory process,and discusses the Cr behavior in eluting process. Experiment results show that Mg can be purified efficiently from Cr and other matrix elements through cluting process once with AG50W-X8 cation resin in 1 mol/L HNO_3medium. The recovery of yielded Mg is higher than 99. 8%,ensuring the accuracy and precision of Mg isotope measurement. In addition,the behavior of Cr during elution process is also discussed. During the separation process,chromium was eluted from the column in early and late two stages respectively,owing to different valence states of Cr in solutions.