MC-ICP-MS法测量铀同位素丰度UH峰校正方法研究

Study on UH Peak Correction Method for Measuring Uranium Isotope Abundance by MC-ICP-MS

由于多接收电感耦合等离子体质谱(MC-ICP-MS)法具有基体耐受性强、精密度高和仪器测量快速的优点,使得采用MC-ICP-MS法分析铀同位素丰度的应用越来越广泛。但是,在MC-ICP-MS法测量铀同位素丰度的分析中,水溶液进样会产生UH多原子离子,而伴随^(235)U^(+)产生的极微量^(235)UH^(+),在质荷比(m/Z)为236处与^(236)U^(+)形成质量双峰,这对于小丰度^(236)U的准确测量会产生干扰,影响^(236)U丰度测量的准确性。本文建立了针对小丰度^(236)U准确测定的UH校正方法,采用该校正方法测量铀同位素丰度,n(^(236)U)/n(^(235)U)丰度比测定下限为4×10^(-6),测量n(^(236)U)/n(^(235)U)丰度比为2.20×10^(-5)的样品时,相对传统热电离质谱法(TIMS)误差小于3×10^(-6),相对标准偏差小于4%。

Due to the advantages of multi-collector inductively coupled plasma mass spectrometry(MC-ICP-MS)such as strong matrix tolerance,high precision,and rapid instrumental measurement,the application of MC-ICP-MS for analyzing uranium isotope abundance has become increasingly widespread.However,in the analysis of uranium isotope abundance using MC-ICP-MS,aqueous solution samples injection can lead to the generation of hydride interference(UH/U).The extremely small amount of^(235)UH^(+)produced alongside^(235)U^(+)results in a molecular interference at m/Z^(236)with^(236)U^(+),which interferes with accurate measurements of low-abundance^(236)U and impacts the accuracy of its abundance determination.In this study,a UH correction method was developed specifically for accurately determining low-abundance^(236)U.The estimated methodological detection limit of n(^(236)U)/n(^(235)U)abundance ratio was estimated to be 4×10^(-6).When measuring a sample with an n(^(236)U)/n(^(235)U)abundance ratio of 2.20×10^(-5),the relative error compared to traditional thermal ionization mass spectrometry(TIMS)was less than 3×10^(-6),and the relative standard deviation was less than 4%.