Szilard-Chalmers effect in holmium complexes

The β-emitting isotope166Ho (T1/2=26.78 h,E(β) max=1.84 MeV) has been studied extensively for the treatment of arthritis and for radioimmunotherapy with labelled antibodies and proteins.166Ho can be produced in quantities sufficient for nuclear medical applications from natural165Ho by activation with thermal neutrons. In the past, time-consuming irradiations in medium and high flux reactors have been performed in order to obtain products with high specific activity. We investigated the production of166Ho using the Szilard-Chalmers reaction in holmium complexes with ligands containing oxygen and nitrogen donor atoms and separated the liberated166Ho3+ by ion exchange and preparative high performance liquid chromatography (HPLC).