Studies on the preparation of a 131Ba-131Cs generator

131Cs has been a useful radionuclide for myocardial scanning and localisation of certain tumors in man. It has a half-life of 9.7 days and is the decay product of 131Ba (T=11.6 d). A 131Ba-131Cs generator was developed based on ion exchange chromatography over hydrous zirconium oxide. Irradiated BaCO3 containing sufficient quantities of 131Cs activity is to be dissolved in calculated quantities of HCl. Enough NH3 and NH4NO3 are added to make the concentration of each to about 0.05 to 0.10M. Preconditioned HZO is taken on a column and the solution is passed down at a slow rate (0.2-0.3 cm3/min). The volume of 131Ba solution is kept as low as possible in order to avoid the elution of 131Cs at this stage. When 131Cs is required the column/generator can be eluted with the eluent, 0.05 to 0.1M NH3 in NH4NO3. This method will yield 131Cs quantitatively and in a pure form free from 131Ba contamination. The 131Cs eluate can be conveniently evaporated and leached with isotonic saline and sterilised before use on human beings. (T.G.)