Investigation of cis-trans photoisomerization of octyl methoxycinnamate by ATR-FTIR spectroscopy

Abstract

In this work, photoisomerization of the UVB filter octyl methoxycinnamate (OMC) on surface was monitored using ATR-FTIR spectroscopy. The study showed that photostationary equilibrium of both the E- to Z-OMC and the Z- to E-OMC was affected by amount of OMC coverage on the surface. More configurational changes were found at lower coverage of OMC. In this work, the configurational change was monitored on ZnSe and rat skin (Mus musculus Linn.) surface. A little more configurational changes were detected on rat skin comparing to on ZnSe surface. At the OMC coverage of 2 mg/cm[superscript 2] or 6.8910[superscript 6] moles/cm[superscript 2] which represents the on skin recommended use of OMC, E to Z configurational change was detected at the UVB irradiance of 0.08 mW/cm[superscript 2] (correspond to UVB irradiance detected in sunlight in Bangkok at noon time on clear sky day). At such condition, photostationary equilibrium of the E- to Z-OMC on rat skin gave the E-OMC: Z-OMC ratio of about 3:1