Most commercial Mo/Tc generators use column chromatography, in which Mo in the form of molybdate, MoO is adsorbed onto acid alumina (AlO). When the Mo-99 decays it forms pertechnetate TcO, which, because of its single charge, is less tightly bound to the alumina. Pouring normal saline solution through the column of immobilized Mo elutes the soluble Tc, resulting in a saline solution containing the Tc as pertechnetate, with sodium as the counterion.
The solution of sodium pertechnetate may then be added in an appropriate concentration to the pharmaceutical kit to be used, or sodium pertechnetate can be used directly without pharmaceutical tagging for specific procedures requiring only the TcO as the primary radiopharmaceutical. A large percentage of the Tc generated by a Mo/Tc generator is produced in the first 3 parent half-lives, or approximately one week. Hence, clinical nuclear medicine units purchase at least one such generator per week or order several in a staggered fashion.