Esr spin trapping evidence for SO^.-₃ and .OH radicals in sulfite oxidation

Electron spin resonanee (ESR) spin trapping experimenss have been carried out to investigate the mechanism of sulfite oxidation employing 5,5-dimethyl-1-pyrroine-1-oxide (DMPO) as a spin trap. The results show that sulfite autoxidation, catalyzed by Mn(II), involves not only the SO^.-₃ radicals but also the .OH radicals. An addition of H₂O₂ to the sulfite aqueous medium significantly increases the .OH radical formation. This result provides new clues to the chemical mechanism of the sulfite oxidation and the sulfite toxicity.