| dc.description.abstract | Astatine, the least abundant naturally occurring element on earth, has attracted interest due to its unique fundamental chemistry and its potential use as an agent in targeted alpha therapy for cancer treatment. Further investigations in these fields rely on the cyclotron production of astatine-211 (At-211), the A=211 isotope of astatine. Traditional production utilizes the 209Bi(α,2n)211At nuclear reaction pathway. This pathway requires a medium or high- energy cyclotron which is necessary to achieve an alpha-particle beam with an energy of 28.8 MeV. There are very few facilities with the capability of producing At-211 which, alongside the small quantity produced in each irradiation, makes the process of recovering At-211 from the natural bismuth target important. Research to advance this process works to maximize the quantity of material available for research. Often, the quantity of At-211 is the limiting factor in experiments involving the element. After production of astatine-211, the irradiated bismuth target must be dissolved (typically in a nitric acid matrix), and the At-211 is then separated from the bulk target material in solution. Current methods, while effective at separating the At-211 from target material, fail to result in free At-211. While achieving the goal of separating the At-211 from the target material and impurities, the At-211 elutes alongside organic molecules which have a high probability of rebinding to the At-211. This complicates subsequent studies as it interferes with the species being studied and therefore misrepresents the behavior of the astatine. When there is such a small quantity of material and a short window to work within, like with At-211, these issues can greatly affect the trajectory of an experiment. In this thesis, there is a focus on designing and researching an alternative method of chromatographic separation using an ion-exchange resin. Two ion-exchange resins, Dowex 50x4 and MP Thiol, within varying nitric acid concentration matrices were tested. At-211 and the metal species previously found in the target dissolution solution were measured and quantified. This data provided information of the affinities the resins exhibited for each species at a given nitric acid condition. Based on these affinities, both ion-exchange resins tested show promise. Additionally, nitric acid concentrations of about 2-3 M look to be the best conditions for loading. Further experimental design for column study experiments can be developed and tested based on these results. Column studies designed with this data in mind will allow testing of various reagents to ultimately find a striping agent to elute the At-211. Once an appropriate stripping agent has been identified, this method will result in free, unbound At-211. | |
