99mTc gel generators based on zirconium molybdate-99Mo: III: Influence of preparatory conditions of zirconium molybdate-99Mo gel on generator performance

The effect of subtle variations on zirconium molybdate-99Mo gel preparatory conditions, such as stoichiometry of reactants, pH of gel formation, conditioning of gel granules etc., prior to elution were investigated primarily to arrive at the conditions resulting in high 99mTc release and minimal 99Mo breakthrough upon elution with normal saline. Zirconium molybdate-99Mo gels were prepared by reacting solutions of Zr and Mo in mole ratios of 0.75-1.5. Both water and normal saline were used for gel disintegration, and the release of 99mTc and 99Mo from gel columns into eluates was compared. Sharper elution profile of 99mTc, but with significantly higher 99Mo breakthrough (5-8 times), was obtained when water alone was used for disintegration and elution, in comparison to when saline was used. Gels exhibiting optimum characteristics were found to be formed at a pH of 4-5 by reacting [Zr]: [Mo] in the mole ratio of 1.25: 1 and after drying, the product was dispersed into granules by disintegration with normal saline. 99mTc elution efficiency was found to be ∝ 75% and 99Mo breakthrough ∝ 0.05%. The elution profile was sharp when a 6 g gel column coupled to a 2 g acidic alumina column (to trap 99Mo) was eluted with 6-9 ml normal saline. Generators containing upto 23 GBq 99Mo were prepared, eluted extensively without changing the alumina column and found to provide pertechnetate of good quality, commensurate with hospital radiopharmacy requirements. (orig.)