Contribution of nitric acid and alcohol to the radiolytic degradation of TODGA in Isopar-M

Radiolytic transformations of TODGA (N,N,N',N'-tetra-n-octylamide of diglycolic acid) in Isopar-M significantly depend both on the addition of alcohol (n-nonanol or n-decanol) and on the saturation of the solution with 8 M HNO3. Fragmentation of TODGA molecules is the dominant radiolytic process. Compared to acid-free solution, radiolysis in the presence of HNO3 results in a much lower yield of N,N-dioctylacetamide formation, while 2-hydroxy-N,N-dioctylacetamide remains the main degradation product of TODGA. The acidification of the solution promotes a lower radiolytic degradation of TODGA, but expands the range of final radiolysis products, in particular, due to the participation of NO2 and NO radicals in radiation-induced reactions. Alcohol serves as a source of alkoxy radicals, which are highly reactive towards TODGA. In the presence of nitric acid, a significant portion of alkoxy radicals decay in reactions with NO2, NO, and acyl radicals and, thus, do not participate in the decomposition of TODGA.