Production of no-carrier-added ¹³⁵La at an 18 MeV cyclotron and its purification for investigations at a concentration range down to 10^-15 mol/L

The production of non-commercially available ¹³⁵La by proton irradiation of an isotopically enriched [¹³⁵Ba]BaCO₃ target at a cyclotron is described. The purification of the radionuclide was performed by a La-selective resin. ¹³⁵La was separated in no-carrier-added (n.c.a) form in a nitric acid solution with a radiochemical yield of 83% ± 5% and a total activity per batch of 43 MBq ± 3 MBq. The enriched [¹³⁵Ba]Ba was recycled to the carbonate form with a recovery of 90% ± 3%. On the basis of a detection limit of 1 Bq/ml, solutions of n.c.a. ¹³⁵La could be measured down to the 10^-15 mol/l concentration range.