Chemical aspects for the development of radionuclide generators

After a short presentation of the basis for the development of radionuclide generators the characteristic properties and fields of application are described. The requirements of medicine are investigated in particular. The aspects for the selection of suitable mother-daughter systems for radionuclide generators are discussed. 85 systems are presented and divided into 4 groups: easily producible radionuclides (without α-emitters), radionuclides producible with some difficulties (without α-emitters), radionuclides producible with appreciable difficulties (without α-emitters) and radionuclides decaying into α-emitters. Then the radionuclide generators are analysed according to the position of the mother nuclide and the daughter nuclide in the periodic table of the elements, in order to make clear the chemical background for the separation. The following separation methods are discussed: precipitation and coprecipitation, solvent extraction, destillation and sublimation, ion exchange and chromatography. The influence of the equilibria involved, given by the distribution coefficients, and of the kinetics, that means the rate of reaching equilibria, are illustrated for ion exchange and chromatographic methods. The development and the chemical investigation of the radionuclide generators 99Mo/99mTc and 137Cs/137mBa are presented as examples. In this connection the problems of purity and safety of handling are discussed. (orig.)