Investigation of a tellurium-packed column for isolation of astatine-211 from irradiated bismuth targets and demonstration of a semi-automated system

Astatine-211 is an attractive radionuclide for use in targeted alpha therapy of blood-borne diseases and micrometastatic diseases. Efficient isolation methods that can be adapted to robust automated 211 At isolation systems are of high interest for improving the availability of 211 At. Based on the early studies of Bochvarova and co-workers involving isolation of 211 At from irradiated thorium targets, we developed a method for 211 At isolation from bismuth targets using tellurium-packed columns. Dissolution of irradiated bismuth targets is accomplished using HNO 3 ; however, 211 At is not captured on the Te column material in this matrix. Our method involves slow addition of aqueous NH 2 OH·HCl to the Bi target dissolved in HNO 3 to convert to a HCl matrix. The amount of NH 2 OH·HCl was optimized because (1) the quantity of NH 2 OH·HCl used appears to affect the radiolabeling yield of phenethyl- closo -decaborate(2-) (B10)-conjugated antibodies and (2) reducing the volume of NH 2 OH·HCl solution can effectively shorten the overall isolation time. A proof-of-concept semi-automated process has been demonstrated using targets containing ~0.96 GBq (~26 mCi) of 211 At. High isolation yields (88–95%) were obtained. Radiochemical purity of the isolated 211 At was assessed by radio-HPLC. Concentrations of Bi and Te contaminants in the 211 At and the astatinated antibodies were evaluated using ICP-MS.