Plutonium, protactinium, uranium and thorium isotopes determination in environmental samples by SF ICP-MS

Abstract

Alpha spectrometry is the most commonly used analytical tool for the determination of Pu, Am, Pa, U and Th long live radionuclides. Thermal ionization mass spectrometry (TIMS) and acceleration mass spectrometry (AMS) are also still considered as primary methods for the determination of their isotope ratios. Spectrometers with plasma ion sources now offer another efficient alternative method with the development of sector field inductively coupled plasma mass spectrometry (SF ICP-MS). This paper summarizes the development work performed and results obtained using this technique for the analysis of such radionuclides. Isotopic ratios and ultra trace levels of man made radionuclides like 239, 240, 241 plutonium but also naturally occurring species like 231 protactinium, 234, 235, 238 uranium and 230, 232 thorium were determined in different field samples and reference materials using a micro concentric nebulizer as an introduction system for the mass spectrometer. Prior to the mass spectrometric measurements these elements were isolated from major elements by different selective precipitations. In further steps, they were purified by anion exchange. Results of isotope ratios including plutonium ones are also discussed.