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

The article presents a novel gas-chemical approach for ²²⁵Ac/²¹³Bi generators, which provides effective separation of ²¹³Bi from parent ²²⁵Ac. 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) ²²⁵Ac 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 ²¹³Bi 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 ²²⁵Ac/²¹³Bi generators for its application in targeted alpha therapy.