Potential Column Chromatography Generators for Ionic Ga-68. I. Inorganic Substrates

Chemical separations for Ga-68 from Ge-68 using adsorption chromatography on inorganic materials are described. The adsorbents used were TiO2, ZrO2, and SiO2. Distribution coefficients for Ge and Ga on these absorbents were determined as a function of reagent concentration and duration of equilibration. The distribution coefficient (w/w) for Ge on SiO2 reached 250 in 6 N HNO3, whereas Ga was no significantly adsorbed. Therefore, Ga-68 can be collected with a mall volume of 6 N HNO3 eluent. By contrast, large volumes of 1 N HNO3 were necessary to collect Ga-68 from ZrO2, since the KD of Ga under these circumstances was about 50. The Ga-68 eluted from TiO2 was chemically contaminated with titanates and would require additional chemical manipulation in order to make it injectable. All the adsorbents could lead to chromatographic systems that would allow acceptable chemical separations. However, the specific requirements for a radionuclide generator, usable in a hospital environment, make the SiO2-based system the most attractive.