Gas-chemical approach to 225 Ac/ 213 Bi radionuclide generator for medical application

The article presents a novel gas-chemical approach for Ac/ Bi generators, which provides effective separation of Bi from parent Ac. The main problem with the generators of high activity is the radiation stability of sorbents, which is not substantial in this gas-chemical method of separation, where only radiationally stable inorganic materials are used. The approach includes heating at high temperature (about 900-1000 °C) Ac sample deposited on a backing material (Nb, quartz glass, stainless steel) in hydrogen-containing inert gas flow. Actinium is non-volatile in these conditions, while Bi sublimes and is deposited on a catcher-foil along a temperature gradient. Niobium was found to be the best of the used material for both the starting backing and catcher-foil. The effective activation energy of carrier-free amount of Bi-sublimation from Nb-backing as 102 ± 9 kJ/mol has been calculated, and standard enthalpy of desorption of Bi on Nb from thermochromatographic data has been evaluated as 269 ± 13 kJ/mol Bi may be recovered for the consequent preparation of radiopharmaceuticals by washing from the catcher-foil surface. The gas-chemical method has been demonstrated to be a promising approach for Ac/ Bi generators for its application in targeted alpha therapy.