铕浓缩同位素全蒸发-1012 Ω高阻信号放大器的热电离质谱分析方法

Total Evaporation Method Using Faraday Cup Coupled to 1012 Ω Current Amplifier for Isotope Abundance Analysis of Isotopically Enriched Europium

  • 摘要: 浓缩同位素是校正质谱法、同位素稀释质谱法和双稀释剂法等同位素质谱分析技术的基础,其化学纯度及丰度量值的准确性直接影响着分析结果的准确性。但由于浓缩同位素中低丰度同位素的离子信号较难准确测量,且缺乏合适的标准物质校正,给高精准的同位素丰度分析带来挑战。本文建立了适用于微量铕浓缩同位素样品纯化的锌还原萃取色层法,纯化后的151Eu和153Eu两种浓缩同位素纯度优于99.99%,有效消除了其他稀土元素杂质的干扰。通过采用1012 Ω信号放大器的法拉第杯接收样品中的低丰度同位素离子信号,建立了铕浓缩同位素的全蒸发热电离分析方法。两种浓缩同位素样品的主丰度测量结果分别为151Eu 0.968 367 6(11)和153Eu 0.987 685 1(21),测量重复性比1011 Ω信号放大器的法拉第杯以及文献中校正质谱法的测量结果提高了3倍。

     

    Abstract: Enriched isotopes are the basis of calibration mass spectrometry, isotope dilution mass spectrometry and double spike method. Their chemical purity and abundance accuracy greatly affect the performance of methods. However, it remains great challenge for high quantity enriched isotopic abundance analysis due to the large abundance difference and the lack of suitable certified reference materials (CRMs). Developing a new analytical method for enriched isotopic abundance analysis is highly necessary and urgent. Total evaporation thermal ionization mass spectrometry (TE-TIMS) is a theoretically calibration free method as its mass fractionation is overcame through sample total evaporation and signal integration, which is the ideal choice for enriched isotope abundance analysis. In this work, two kinds of enriched europium isotopes were purified by zinc reduction-extraction chromatography based on the significant different chemical properties between Eu2+ and other trivalent rare earth elements (RE3+). After purification, the purity of those two enriched europium isotopes is better than 99.99%. Subsequently, a total evaporation method was established for enriched europium isotope abundance analysis using Faraday cup coupled to 1012 Ω current amplifier for the minor isotope, while using Faraday cup coupled to 1011 Ω current amplifier for the major one. The measured abundance of 151Eu and 153Eu are 0.968 367 6 (11) and 0.987 685 1 (21), respectively, whose reproducibility is 3 times better than that obtained using 1011 Ω current amplifier or that obtained using calibration mass spectrometry reported before. This work proposes a novel method for enriched europium isotope analysis, which can be applied for the analysis of other enriched isotopes.

     

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