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POTENTIOMETRIC and LASER FLASH PHOTOLYSIS STUDIES OF THE pH DEPENDENCE OF HYDROGEN PEROXIDE PRODUCTION BY THE SEMICARBAZIDE/LUMIFLAVIN/OXYGEN PHOTOSYSTEM
Author(s) -
Navarro José A.,
Roncel Mercedes,
Rosa Miguel A. De la
Publication year - 1987
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1987.tb04878.x
Subject(s) - chemistry , photochemistry , semicarbazide , hydrogen peroxide , flash photolysis , quenching (fluorescence) , oxygen , disproportionation , photodissociation , triplet state , inorganic chemistry , kinetics , fluorescence , catalysis , organic chemistry , reaction rate constant , molecule , physics , quantum mechanics
The effect of pH on hydrogen peroxide photoproduction by the semicarbazide/lumiflavin/ oxygen system has been investigated by using the potentiometric and laser flash photolysis techniques. Kinetic analysis of (a) primary and secondary reactions involved in the photoreduction of lumiflavin and (b) lumiflavin reoxidation by oxygen have been carried out at varying pH values, drastic differences being observed in the pH dependence of both types of reactions. The reaction mechanism appears to proceed by semicarbazide‐quenching (reductive type) of the light‐excited lumiflavin in its triplet state followed, depending on pH, either by reoxidation of the so formed flavosemiquinone by molecular oxygen or by flavosemiquinone disproportionation into oxidized and fully reduced lumiflavin.