High radioactive concentration of 99mTc from a zirconium [99Mo]molybdate gel generator using an acidic alumina column for purification and concentration

BackgroundNewer applications of radiopharmaceuticals in nuclear medicine require pertechnetate of moderate to high radioactive concentration. Hence there is a need to develop simple procedures for the concentration of pertechnetate, and such a procedure is given in this paper. MethodsTen to 20 ml of sodium [99mTc]pertechnetate eluted in de-ionized water from a zirconium [99Mo]molybdate (Zr99Mo) gel column generator was passed through 2 g of an acidic alumina bed (35×8 mm) in order to remove the co-eluted traces of 99Mo and to retain the pertechnetate. The retained pertechnetate was then re-eluted, quantitatively, in 3 ml of normal saline, from the alumina column. ResultsAbout a 4-fold increase in radioactive concentration of 99mTc was obtained (cf. ∼10–12 ml normal saline is required for the elution of 99mTc from the gel column). Generators containing up to 22.2 GBq (600 mCi) 99Mo in 6–7 g Zr99Mo gel column (35×13 mm) were prepared and a radioactive concentration of 99mTc up to 4 GBq·ml−1 (110 mCi·ml−1) was obtained on the first day of use. The overall recovery of 99mTc was >90%, 99Mo breakthrough was 10−3 to 10−4% and the duration of concentration was 3–5 min. The chemical impurity in terms of Al, Mo and Zr was <10 ppm each. The same procedure for the concentration of pertechnetate was applied to generators with 12–15 g Zr99Mo gel beds to obtain a higher capacity 99mTc gel generator, with similar findings.