[en] On average 80% of the radiopharmaceuticals used in Nuclear Medicine are labeled with ⁹⁹mTc due to its physical properties and easy attainment through of ⁹⁹Mo/⁹⁹mTc generators. The Directory of Radiopharmacy (DIRF) of IPEN-CNEN/SP developed a gel type chromatographic generator of MoZr with ⁹⁹Mo produced by ⁹⁸Mo(n,γ)⁹⁹Mo reaction that occurs at the IEA-R1 Nuclear Reactor. The gel is composed of zirconium molybdate with elution volume of 12 mL with an activity of 11100 MBq (300 mCi) producing a radioactive concentration of 925 MBq (25 mCi)/mL. The fission generator gives a higher radioactive concentration around 1850 MBq (50 mCi)/mL. The aim of this work is to study a system of post-elution concentration of ⁹⁹mTc for the attainment of a high enough radioactive concentration to meet the demands of the market, with a proved quality. Two types of systems of post-elution concentration were developed: the single and the tandem. The most appropriate system for the gel generator of ⁹⁹Mo/⁹⁹mTc, being at the same time sterile and vacuum automated, was the tandem system using Dionex 2.5 cc/QMA cartridges. The gel generator is eluted with 10 mL of solution of 0.1% NaCl and the pertechnetate anion is retained in the QMA cartridge and further eluted with 4 mL of saline. The process takes no more than 30 minutes. The elution efficiency of the system of concentration was 90 %. At the beginning of 2009 a global crisis in the supply of ⁹⁹Mo took place making it necessary the development of alternative technologies for the production of ⁹⁹Mo/⁹⁹mTc generators using fission produced ⁹⁹Mo and the development of an appropriate method to extend the useful life of this generator. The results of this study showed that the same system developed for the post- concentration of the gel generator can be employed for the fission generator, using the tandem system, giving a concentration factor of 3 for the elution of ⁹⁹mTc. (author)