Abstract: A method of producing high concentrated 99mTc solution has the steps of dissolving 99MoO3 pellet with alkali solution; extracting 99mTc from the dissolved solution with ketone type organic solvent; separating an ketone type organic phase containing 99mTc and an aqueous phase; adsorbing and concentrating the separated ketone type organic phase containing 99mTc after removing impurities, through a basic alumina column for impurity removal and an acidic alumina column for adsorption and concentration connected continuously; and eluting 99mTc from the acidic alumina column to which 99mTc is adsorbed by physiological saline, wherein the alkali solution is 6M-NaOH solution or 6M-KOH solution.

Abstract: Mo adsorbent for .sup.99 Mo-.sup.99m Tc generators has a skeleton structure having mainly repeating units represented by the general formula; ##STR1## wherein X is a halogen atom or alkoxide group having one to six carbon atoms, 10% or more of X is halogen, R is an alkylene, polymethylene, or carbon chain having unsaturated bond, repeating unit (D) is bonded to any one of repeating units (A), (B), and (C), the branch structure is controlled by the content of repeating units (A), (B), and (C), the adsorbent is insoluble in water and adsorbs selectively only Mo from an aqueous solution containing Mo, and elutes .sup.99m Tc generated from a radioactive isotope .sup.99 Mo. This Mo adsorbent uses .sup.99 Mo obtained from natural Mo by (n, .gamma.) method, therefore, a generator having the same size as conventional .sup.99m Tc generators is realized.