Actinometric assignment of skin protection factor (SPF) values to a range of aromatic alkyl alkanoates

Abstract

As a result of stratospheric ozone depletion, more ultraviolet (UV) radiation reached the earth’s surface with consequent adverse effects on human health. For this reason, sunscreen product usage has become crucial for sun protection as they absorb harmful UV radiation. The photoreduction of benzophenone with 2-propanol is a well know photochemical reaction that has been used for the synthesis of benzpinacol and was used throughout this project with the goal of creating a calibration curve (actinometry) using commercial sunscreens. The parameters of this experiment were optimized to achieve the first point on the curve, but upon testing other sunscreens, insufficient data was collected to create the desired actinometric curve of fractional quantum efficiency versus Sun Protection Factor (SPF) value. For this reason, the calibration curve produced by a similar study by Rolls (2000) was used to deduce the SPF values of methyl salicylate, octyl salicylate, and benzocaine- all common active ingredients in commercial sunscreens- prepared via Fisher Esterification. Octyl salicylate was the only aromatic alkyl alkanoates tested that yielded benzpinacol and the SPF value was found to be 90.