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Unexpected Photolysis of the Sunscreen Octinoxate in the Presence of the Sunscreen Avobenzone ¶
Author(s) -
Sayre Robert M.,
Dowdy John C.,
Gerwig Andre J.,
Shlelds William J.,
Lioyd Roger V.
Publication year - 2005
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.1751-1097.2005.tb00207.x
Subject(s) - photodegradation , photochemistry , uv filter , irradiation , chemistry , ultraviolet , photodissociation , transmittance , electron paramagnetic resonance , ultraviolet visible spectroscopy , radical , degradation (telecommunications) , materials science , photocatalysis , organic chemistry , optoelectronics , optics , nuclear magnetic resonance , telecommunications , physics , computer science , nuclear physics , catalysis
A major concern raised about photostability studies of sunscreen products is that the photodegradation of sunscreens does not readily translate into changes in product performance. This study examines the correlation between photochemical degradation of sunscreen agents and changes in protection provided by sunscreen films. Films of a commercial sunscreen product containing avobenzone, oxybenzone and octinoxate were irradiated using a fluorescent UV‐A phototherapy lamp with additional UV‐B blocking filter. Periodically, during irradiation the transmittances of the films were measured and samples collected for chemical analysis of the sunscreen agents using high‐performance liquid chromatography techniques. The results show that UV‐induced changes in UV transmittance of sunscreen films correlate with changes in concentration of sunscreen agents. In a parallel experiment, we also irradiated a thin film of the same product in the cavity of an electron spin resonance (ESR) spectrometer. We report the concomitant photolysis of avobenzone and octinoxate that predominates over expected E/Z photoisomerization and that irradiation of a film of this product produced free radicals detected by ESR spectroscopy that persisted even after exposure had ended.