Procedures for the separation, purification, and high-precision analysis of mass-independent isotopic variations in molybdenum (Mo) using negative thermal ionization mass spectrometry are reported. Separation and purification of Mo from silicate and metal matrices are achieved using a two-stage anion exchange chromatographic procedure. Molybdenum is ionized as the MoO3 - species using a double filament assembly. The MoO3 - ion beams are collected using Faraday cup detectors equipped with a mixed array of amplifiers utilizing 1011 and 1012 Ω resistors, which allows for in situ measurement and correction of oxygen isobars. The long-term external reproducibility of 97Mo/96Mo, the most precisely measured Mo isotope ratio, is ±5.4 ppm (2SD), based on the repeated analyses of the Alfa Aesar Specpure ® Mo plasma standard and using 98Mo/96Mo for fractionation correction. The long-term external reproducibilities of 92Mo/96Mo, 94Mo/96Mo, 95Mo/96Mo, and 100Mo/96Mo are ±107, 37, 23, and 32 ppm (2SD), respectively. With this precision, smaller differences in Mo isotopic compositions can be resolved than have been previously possible.

中文翻译：

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负热电离质谱法高精度钼同位素分析

报告了使用负热电离质谱法对钼 (Mo) 中与质量无关的同位素变化进行分离、纯化和高精度分析的程序。使用两阶段阴离子交换色谱程序从硅酸盐和金属基质中分离和纯化 Mo。钼被电离为 MoO3 - 使用双灯丝组件。MoO3 - 离子束是使用法拉第杯检测器收集的，该检测器配备了使用 1011 和 1012 Ω 电阻器的混合放大器阵列，允许原位测量和校正氧等压线。97Mo/96Mo 的长期外部重现性是最精确测量的 Mo 同位素比，为 ±5.4 ppm (2SD)，基于对 Alfa Aesar Specpure ® Mo 等离子体标准的重复分析，并使用 98Mo/96Mo 进行分馏校正。92Mo/96Mo、94Mo/96Mo、95Mo/96Mo 和 100Mo/96Mo 的长期外部重现性分别为 ±107、37、23 和 32 ppm (2SD)。以这种精度，可以解决比以前更小的 Mo 同位素组成差异。