A Correction Method for the Peak Tailing Backgrounds for Accurate Isotope Ratio Measurements of Uranium in Ultra Trace Levels using Thermal Ionization Mass Spectrometry

Abstract

A new method in thermal ionization mass spectrometry (TIMS) was developed to correct peak tailing backgrounds in the isotope ratio measurements of uranium in ultra trace levels for higher accuracy. Two different uranium standard reference materials (U005 and U030) were used to construct databases of signal intensities at mass 234 u and mass 236 u, which correspond to the two uranium minor isotopes, and signal intensity of 238 U. Correlations between peak tailing backgrounds and 238 U were obtained by least-squares regression on calculated backgrounds at mass 234 u and mass 236 u with respect to the signal intensity of 238 U followed by separation of the peak tails of the two major isotopes of uranium ( 235 U and 238 U), which enables us to obtain a master equation for peak tailing background correction on all kinds of samples. Verification of the correction method was carried out using U010 and IRMM-040a.

Determination of the Concentration and Isotope Ratio of Uranium in Soil and Water by Thermal Ionization Mass Spectrometry

“…One microliter of each sample was loaded onto individual rhenium filaments (zone-refined, Thermo Scientific) and fixed at 1.8 A for 30 s. 16,17 The uranium background of each filament had been minimized prior to use. The system was pumped for at least 5 h after loading the filaments and prior to acquiring TIMS data.…”

“…The experimental setup has been described in detail elsewhere. 16,17 Multi-dynamic measurements utilizing a secondary electron multiplier (SEM) and Faraday cups were used with the soil samples and the hot spring water sample. Dynamic measurements, in which the magnetic field was regulated using an SEM to receive ion signals from each individual isotope, were used with the ground water sample.…”

Isotopic Analysis of NUSIMEP-6 Uranium Particles using SEM-TIMS

“…7,8,9 Four channeltrons in a multiple ion counter (MIC) system were used to detect the ion signals of the four isotopes of uranium simultaneously.…”

Feasibility of Using Graphite Powder to Enhance Uranium Ion Intensity in Thermal Ionization Mass Spectrometry (TIMS)

“…[15][16][17][18][19] The maximum intensity (in mV) within each measurement was recorded to compare between carburization conditions. Due to the lack of reproducibility in TIMS ion intensity, multiple measurements of the same samples were performed.…”