Yttrium-90 Radiolabelling of Biotin DOTA

Yttrium-90 1,4,7,10-tetraazacyclododecane 1,4,7,10-tetraacetic acid (DOTA) biotin was prepared by adding an equal volume of sodium acetate (1.0M, pH5.0) to the ⁹⁰YCl₃ vial (concentration 37–74 GBq/mL in 0.05M HCl) containing 2.96–4.44 GBq of ⁹⁰Y followed by 1.0 mg of biotin DOTA dissolved in 0.5 mL of saline (recommended specific activity of 3.7 GBq/mg). After mixing, the reaction vial was incubated for 30 min at 95°C. Aliquots of the mixture were drawn at defined time intervals to determine the radiochemical purity (RCP)