How Radiolysis Impacts Astatine Speciation?

This work deals with the impact of chloroform radiolysis on astatine chemistry. Astatine-211 is a promising radionuclide for the targeted alpha therapy of cancers. Yet, the production of At-211 based radiopharmaceuticals is often complicated by radiolysis due to its own decay, leading to solvent degradation and then impacting astatine chemical state and radiolabeling efficiency. A better understanding of the radiolysis phenomenon is thus necessary. Two experiments are performed: (1) pH measurement during the At extraction in chloroform medium, (2) pH determination calculated from the HCl chemical yield which is obtained during the radiolysis of chloroform medium by gamma-ray. In both cases, the pH values are determined at 2.0 & PLUSMN; 0.5. Then, it is possible to predict the acidic conditions during the At-211 production by HCl radiolytic yield determination. This work demonstrated that the radiolysis induced by At during its production in CHCl3 medium should be taken into account as it has a significant effect on acid-basic conditions. The work helps understanding the mechanisms of production of a major impurity generated from At-211 radiolysis in chloroform which alters its radiochemistry, allowing for the identification of solutions to counteract these unwanted effects.