Preparation and characterization of ¹⁶⁹ErCl₃ radioisotope from irradiated 97.75% enriched erbium-168 target

Erbium-169 (¹⁶⁹Er) is one of radioisotopes that can be used for radiosynovectomy due to its β particle emission. The preparation of ¹⁶⁹ErCl₃ radioisotope has been developed by irradiation of enriched erbium oxide target with 97.75% of ¹⁶⁸Er enrichment. Before it is used in radiopharmaceuticals preparation, the ¹⁶⁹ErCl₃ solution was characterized to fulfil its application criteria. The physico-chemical characterization of ¹⁶⁹ErCl₃, including solution clarity; pH; electric charge; the radiochemical purity; and the radionuclidic purity, were determined by visual observation; pH indicator paper; paper electrophoresis technique; paper chromatography and paper electrophoresis techniques; and multichannel γ spectrometry, respectively. The stability of ¹⁶⁹ErCl₃ solution was determined by daily observation of radiochemical purity during one month at room temperature. The present study has shown that ¹⁶⁹ErCl₃ was a clear solution, the pH of 1.5 - 2, neutral, the radiochemical purity of 99.51 ± 0.41 % and radionuclidic purity of 99.84 ± 0.1 %. The solution had specific activity and radioactive concentration of 1.26 - 3.38 mCi/mg Er and 11.05 - 29.59 mCi/mL at the end of irradiation (EOI), respectively. Stability evaluation indicated that ¹⁶⁹ErCl₃ solution was still stable for one month at room temperature with radiochemical purity of 99.65 ± 0.09%. Based on the results, ¹⁶⁹ErCl₃ solution from enriched erbium oxide target with 97.75% of ¹⁶⁸Er enrichment has suitable physico-chemical characteristics for radiosynovectomy. (author)