Rapid determination of Sr-90 impurities in freshly generator eluted Y-90 for radiopharmaceutical preparation

Y-90 is one of the most useful radionuclides for radioimmunotherapeutic applications and has a half-life (t(1/2) = 64.14 h) suitable for most therapeutic applications, beta particles of high energy and decays to a stable daughter. it is significant that Y-90 is available conveniently and inexpensively from a radionuclide "generator" by decay of its parent, Sr-90. Nevertheless, current and planned clinical applications with [Y-90] labelled compounds employ activity levels that cannot be readily obtained from an in-house generator, but from commercial sources. We have evaluated Eichrom's Sr-resin, either as an "in-house" generator or as a fast QC method for analysis of Y-90 solutions. In particular, for the development as a generator, we investigated the percentage of the radio-Sr in the first 8 M HNO3 eluate: in this fraction the concentration of Sr-90 must be smaller than 10(-5)% (recommendations of the International Commission on Radiological Protection). For evaluation as a rapid QC method, we analyzed the concentration of Y-90 in all the fractions containing "only" radio-Sr: Y-90 should not be present in these eluates. After the collection of beta(-) and gamma spectra and analysis of them, we concluded that commercial Sr-resin minicolumn cannot give us the results expected; we developed an in-house system loaded with 4 mL of Sr-resin which gave better results as a generator and a rapid QC method.