Solid phase extraction-based separation of the nuclear isomers ^177mLu and ¹⁷⁷Lu

A solid phase extraction based ^177mLu-¹⁷⁷Lu separation method has been investigated for its feasibility to be used in the radionuclide generator. The use of 2,2',2"-(10-(2,6-dioxotetrahydro-2H-pyran-3-yl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetic acid, (DOTAGA-anhydride) allowed grafting of DOTA (1,4,7,10-tetraazacyclododecane N,N',N″,N‴-tetraacetic acid) complex on the surface of commercially available amino propyl silica. The grafting of DOTA has been confirmed by several characterization techniques. The thermogravimetric analysis reveals that the 0.33 mmol DOTA groups have been grafted per gram of silica. However, during the Lu ion complexation, a 10 times lower Lu adsorption capacity of 0.03 mmol g^-1 could be achieved under the studied reaction conditions. The results indicate that the grafting of DOTA on solid affects the Lu coordination and also influences the kinetics of Lu-DOTA complexation. The weak coordination resulted in high ^177mLu leakage, while the unreacted DOTA groups interfer with the ¹⁷⁷Lu release. This is evident from the 0.3% ^177mLu leakage combined with a¹⁷⁷Lu extraction efficiency of 25%. Overall, the results show a^177mLu-¹⁷⁷Lu separation with a maximum ¹⁷⁷Lu/^177mLu activity ratio of 25. But this is still far away from clinically acceptable activity ratio of 10,000 for which future work is recommended.