Among the natural isotopes of radium, Radium 226 is one of the most radiotoxic agent. It is part of the decay chain of Uranium 238 and, with a half-life of 1600 years, it is the most common isotope of Radium present on Earth. Due to its chemical properties, the metabolic pathway of Radium is similar to that of Calcium and it can concentrate mainly in the bones and thus increase the internal dose and the risk of occurrence of certain diseases. For this reason, Radium 226 is of paramount importance in the field of radiation protection.
In order to optimize its environmental monitoring and to better understand its biogeochemical dynamics and to quantify its transfer, the analysis of Radium 226 at the lowest possible levels is necessary. Our aim was to implement an analytical procedure complying with the requirements of environmental monitoring and radioecological studies all over French territory, but also to assess a robust protocol for accidental or post-accidental situations, where higher activity levels are expected. One way for lowering detection limits is to measure this radioactive isotope by inductively coupled plasma mass spectrometry (ICP-MS).
In this context, we choose to develop Radium-226 analysis by ICP-MS in environmental liquid matrices. The selection of the internal standard, the influence of the interfering species on the measurement and the ICP-MS measurement parameters will be discussed. The protocol has been tested with standard solutions and proficiency test samples, and showed very good accuracy.
A comparison of the analytical performances of mass spectrometry versus radiometric methods (limit of quantification, time of analysis...) demonstrates the strengths of radium-226 analysis by ICP-MS.