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

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.