More than ten percent ionization efficiency for Tc measurement by negative thermal ionization mass spectrometry†
The accurate determination of ultra-trace amounts of 99Tc is still a challenge due to its long half-life and the lack of a commercially available isotopic tracer. Negative thermal ionization mass spectrometry (N-TIMS) has been proven to be a powerful method for the analysis of isotopes with relatively high ionization potentials. In this work, we established a novel method based on N-TIMS for the measurement of Tc isotopes. By using Pt filaments and Ba(OH)2 as the ionization activator, the ionization efficiency of Tc was significantly improved to be more than 10%. The oxygen isotopic compositions were measured with a 99Tc standard solution and the obtained coefficients can be applied directly for the correction of interferences from oxygen isotopes. We used this method for the measurement of the isotopic abundance and concentration of the 97Tc tracer produced in our laboratory. Due to the high ionization efficiency of this method and the calibration of the 97Tc tracer, ultra-trace determination of 99Tc in radioactive wastes and environmental samples is now possible.