Analytical determination of radium isotopes in water: current capabilities, challenges and future directions

Radium isotopes in water remain a significant analytical challenge due to their low environmental activity concentrations, chemical similarity to alkaline-earth elements, and strict regulatory limits. Accurate determination of ²²⁶Ra and ²²⁸Ra requires efficient preconcentration and selective radiochemical separation prior to detection. This review evaluates contemporary methodologies for radium isotope determination in water, with particular emphasis on developments reported since 2014. Special attention is given to preconcentration strategies, radiochemical isolation procedures, source preparation and measurement techniques, as well as to how these steps influence analytical performance in terms of ingrowth time, counting time, recovery and minimum detectable activity concentration. Overall, this review provides a critical framework for selecting appropriate analytical methods for environmental monitoring and regulatory applications, by critically comparing complete analytical workflows and highlighting the parameters which control analytical performance.