ESR spin trap investigations on aqueous glucose solutions irradiated by ultrasound and gamma-rays

Applying 5,5-dimethylpyrroline-N-oxide (DMPO) as the spin trap, the radical adducts produced by ultrasound and γ-irradiation of water and aqueous solutions of d-glucose are compared. In the ESR-spectra obtained for sonolysis and radiolysis of water, H- and OH-adducts are present. In glucose solutions for both types of irradiation the H-adduct is also detected. However, OH-adduct is completely lacking and there is no evidence for the formation of adducts originating from glucosyl radicals. To explain these experimental observations the following mechanism is proposed: the OH- and H-radicals produced by sonolysis or radiolysis in water abstract carbon bond hydrogens from glucose generating glucosyl radicals. This explains the lack of OH-adducts. The glucosyl radicals stabilise by H-transfer to the spin trap. This explains the presence of H-adducts and the lack of glucosyl-adducts. The splitting constants of three additional radical adducts, which are present in minor concentrations as well in water as in glucose solutions, were evaluated. They are supposed to be spin adducts resulting from H-abstraction from DMPO.