Isotope Measurement of Uranium at Ultratrace Levels Using Multicollector Inductively Coupled Plasma Mass Spectrometry

Seong-Y Oh,Seon-A Lee,Jong-Ho Park,Kyu-Seok Song,Myung-Ho Lee

doi:10.5478/msl.2012.3.2.54

Abstract

Mass spectrometric analysis was carried out using multicollector inductively coupled plasma mass spectrometry(MC-ICP-MS) for the precise and accurate determination of the isotope ratios of ultratrace levels of uranium dissolved in 3%HNO3. We used the certified reference material (CRM) 112-A at a trace level of 100 pg/mL for the uranium isotopic measurement. Multiple collectors were utilized for the simultaneous measurement of uranium isotopes to reduce the signal uncertaintydue to variations in the ion beam intensity over time. Mass bias correction was applied to the measured U isotopes to improve theprecision and accuracy. Furthermore, elemental standard solution with certified values of platinum, iridium, gold, and thalliumdissolved in 3% HNO3 were analyzed to investigate the formation rates of the polyatomic ions of Ir40Ar+, Pt40Ar+, Tl40Ar+,Au40Ar+ for the concentration range of 50–400 pg/mL. Those polyatomic ions have mass-to-charge ratios in the 230–245 m/zregion that it would contribute to the increase of background intensity of uranium, thorium, plutonium, and americium isotopes. The effect of the polyatomic ion interference on uranium isotope measurement has been estimated.

Highlights

Over the past few decades, inductively coupled plasma mass spectrometry (ICP-MS) has been increasingly used for ultratrace elemental analysis owing to its advanced capabilities such as high sensitivity and short measuring time.[1−3] ICP-MS is superior to thermal ionization mass spectrometry (TIMS) in that it provides higher ionization efficiencies for a given sample size; this allows ICP-MS tools to be used widely for uranium(U) isotope ratio measurements at ultratrace analyte levels.[4,5]
Jong-ho Park, Myungho Lee, and Kyuseok Song solutions of Ir, Au, Pt, and Tl diluted in 3% HNO3 (Anapex Co., Ltd.) to investigate the polyatomic ions that might affect the accuracy and precision of the isotopic measurement of actinide elements
We investigated the effect of polyatomic ions that may interfere with the U isotopic measurement

Summary

Introduction

Over the past few decades, inductively coupled plasma mass spectrometry (ICP-MS) has been increasingly used for ultratrace elemental analysis owing to its advanced capabilities such as high sensitivity and short measuring time.[1−3] ICP-MS is superior to thermal ionization mass spectrometry (TIMS) in that it provides higher ionization efficiencies for a given sample size; this allows ICP-MS tools to be used widely for uranium(U) isotope ratio measurements at ultratrace analyte levels.[4,5] The ICP-MS technique is based on the concept that plasma ions, which indicate the presence of an analyte in a sample, are driven by intense electromagnetic fields, and are directed toward their own intrinsic paths by electric and magnetic sector analyzers.[6,7] The ion currents measured by ion collector systems provide valuable information on the isotopic compositions in a sample solution. The effect of the polyatomic ion interference on uranium isotope measurement has been estimated.

Results

Conclusion