Detection of free radicals in illuminated dye solutions by the initiation of sulfite oxidation.

The aerobic oxidation of sulfite thus provides a magnified manometric response to the chain initiating event. Advantage was taken of this circumstance to develop an ultrasensitive assay for milk xanthine oxidase (5). The data obtained were consistent with the hypothesis that xanthine oxidase, when acting on purine substrates, initiates the aerobic oxidation of sulfite by the generation of free radicals (6). Several dyes have been found to initiate the oxidation of sulfite when exposed to light, thus permitting ultrasensitive manometric actinometry (7). It appeared feasible, through the use of flow mixing techniques, to utilize the initiation of the oxidation of sulfite as a device to investigate the stability of the radicals generated in illuminated dye solutions.