Depolymerisation of zirconium in spectrophotometry with arsenazo III

Effect of Zr:Mo ratio on 99mTc generator performance based on zirconium molybdate gels

Zirconium molybdate gels have shown to be viable alternatives for preparation of 99mTc generators using 99Mo produced by neutron activation. The aim of this work was to investigate the effect of the Zr:Mo molar ratio on the gel chemical structure and correlate it with the elution efficiency. A series of gels were prepared at Zr:Mo molar ratios from 0.5:1 to 2.3:1 and characterized by TGA, IR, XRD and UV. It was found that the variation of Zr:Mo ratio produces different polymolybdate arrangements on the octahedral units around to the zirconia which is mainly influenced by the water content. When the matrix molybdenum concentration was increased a lesser amount of water was found and the elution efficiencies were increased. However high elution efficiencies produce higher 99Mo breakthrough values. The gel formulation appears thus to be a compromise between the elution efficiency and the molybdenum breakthrough. The chemical-physical properties of these gels are presented and discussed.

Zirconium molybdate gel as a generator for technetium-99m--I. The concept and its evaluation

A new 99mTc generator for the preparation of radiopharmaceuticals has been developed. Its elution characteristics and chemical stability merit its consideration as a replacement for present generators. The 99Mo is present as a zirconium molybdate gel, the high molybdate content of which allows the use of (n, gamma) 99Mo. The resulting generator is as effective and as convenient to use as chromatographic generators that are based on fission product 99Mo. Laboratory evaluations of the concept at low levels of radioactivity described in this paper show that the gel can be prepared in a form which is stable when used in a generator and from which TcO4- can be eluted in yields of 80-85%. The influence of formulation variables on gel properties was established. The performance of this generator using 99Mo with specific activities between 4 and 13 GBq g-1 is described in a further paper.