Analysis of the kinetic stability of yttrium chelates by free-ion selective radiotracer extraction (FISRE)

Within this work the analysis of the kinetic stability of a series of yttrium complexes, i.e., Y-citrate, Y-NTA, Y-CDTA as well as Y-humic acid (Y-HA) has been successfully performed by the free-ion selective radiotracer extraction (FISRE) method. FISRE uses ⁹⁰Y with a high specific activity to perform CHELEX extractions in a buffered aqueous solution at pH 6 in two different modes by monitoring the dissociation and association reactions of the corresponding complexes. Whereas in the case of Y-citrate the dissociation profile could be successfully described in terms of (pseudo) first order kinetics, the other complexes tend to form two species with different kinetic properties, although only one species is predicted by speciation calculations. In the batch FISRE method, all (except Y-NTA) corresponding association rate constants were determined by monitoring the formation rate of the yttrium complexes.