Production and purification of ⁵⁶Co at the Leipzig cyclotron

⁶⁰Co (T_1/2 = 5.27 a) is one of the most used radionuclide for sterilization of medical equipment, as a radiation source for medical radiotherapy, industrial radiography and food irradiation due to the high gamma-energy of 1.33 MeV. In case of release in the geosphere, e.g. soil and aquatic systems, the migration behaviour of cobalt is not well understood. For geochemical investigations, e.g. migration and adsorption studies in soil and rock formations, the short-lived isotope ⁵⁶Co (T_1/2 = 77 d) can be used.
We produced ⁵⁶Co at a recently installed 18 MeV-cyclotron by using the nuclear reaction ⁵⁶Fe(p,n)⁵⁶Co.^[1] The target was prepared by pressing metallic iron powder into an aluminium plate and cover it with an aluminium foil. After the irradiation with 11 MeV protons for 1 h at a current of 25 µA, the iron was dissolved with a mixture of concentrated HCl and concentrated H₂O₂.^[2] The separation of ⁵⁶Co from the target material was done by liquid-liquid extraction with methyl-tert-butylether (MTBE) from 5.2 M HCl.^[3] Alternatively, an anionic exchange with DOWEX 1x8 as a column material can be used.^[4] Due to the shorter separation time the liquid-liquid extraction is preferred. The radiochemical yield was 82% ± 6%. The activity concentration in the ⁵⁶Co stock solution was ~4.5 MBq / ml.

[1] Jenkins, I. L., Wain, A. G., (1970) J. Inorg. Nucl. Chem. 32(5) 1419-1425.
[2] Lagunas-Solar, M. C., Jungerman, J. A., (1979) Int. J. Appl. Radiat. Isot. 30(1) 25-32.
[3] V. Wiskamp, S. Zenker, (1997), Eisenextraktion mit tertiärem Butylmethylether. CLB 48 (Beilage Memory) 22.
[4] Kraus, K. A., Moore, G. E., (1953) J. Am. Chem. Soc. 75(6) 1460-1462.