Isolation and quantification of a 93Mo isotope solution from proton irradiated niobium

Abstract

93Mo (4000 y half-life) formed through the 93Nb(p,n)93Mo reaction was isolated from a niobium target foil previously used in a low energy medical cyclotron. 93Mo has identical characteristic x-ray emission and mass as the isomer 93mNb and stable Nb present in the target foil at much higher concentrations. This makes distinction between 93Mo, 93mNb and stable Nb difficult using radiometric or mass spectrometric methods. An anion exchange method in combination with x-ray spectrometry and ICP-MS/OES enabled quantitative isolation of about 0.4 μg 93Mo (14 kBq) from 93mNb with a separation factor >104 on a single column. An extraction chromatography column (TEVA) was used to reach a93mNb/93Mo activity ratio of <10−6 and an atom ratio 93Nb/93Mo <1% making the 93Mo suitable for both radiometric and mass spectrometric testing. 93Mo is the only radioisotope of molybdenum with a long enough half-life suitable for this purpose. Calibration of the 93Mo isotope solution was done through x-ray spectrometry using a characterized BEGe-detector in combination with a99mTc solution. This is the first reported isolation of a93Mo solution in the literature and the first time a LSC-spectrum of 93Mo is shown.