Electrochemical separation and purification of yttrium-86

Summary

For quantitative determination of in vivo dosimetry of ⁹⁰Y-labeled radiotherapeuticals by means of PET, the positron emitting analogue yttrium-86 was produced at a low energy (“medical”) cyclotron via the known ⁸⁶Sr(p, n)⁸⁶Y reaction. Using 200 mg of ⁸⁶SrCO₃ (enrichment 95.6%) and protons of 15.1 MeV energy, average yields of ⁸⁶Y of 48 ± 8 MBq/µA h were produced. After dissolution of ⁸⁶SrCO₃ in 3 ml of 0.6 N HNO₃, ⁸⁶Y was deposited in a simple and highly efficient electrochemical two-step procedure onto a platinum cathode at 450 mA (= 20 mA/cm²). The isotope was finally removed from the electrode by 100–300 µl of 0.5–1.0 N HCl or 0.3–0.6 N HNO₃ resulting in an overall recovery of 88 ± 6% (corrected for decay). Up to 1 GBq of ⁸⁶Y with high radionuclidic and radiochemical purity were obtained after a 2.5 h irradiation and a radiochemical separation time of 2 h. An ICP/AES analysis of the separated fraction showed a very small amount of strontium (< 0.1 ppm). The chemical purity of ⁸⁶Y, essential for efficient labeling, was successfully demonstrated by means of complex formation with DOTA and a DOTA-conjugated peptide, exhibiting labeling yields higher than 98%.