High-performance liquid chromatographic method for the comparison of the photostability of five sunscreen agents

Abstract

Sunscreen agents are commonly used in cosmetic products to filter out noxious radiation in sunlight. A convenient high-performance liquid chromatographic (HPLC) method for the quantification of five sunscreens after irradiation has been selected. We used this analytical method to compare the photostability of benzophenone-3, PEG-25 PABA, octyl dimethyl PABA, 4-methylbenzylidene camphor and butyl methoxydibenzoylmethane, at levels in the range of 25–60 μ M. The assay was carried out, using a C 8 column with a methanol–water mobile phase. The detector was set at a wavelength of 300 nm. The assay was linear with the following limits: 0.2 μg ml −1 for benzophenone-3, 1 μg ml −1 for PEG-25 PABA, 0.15 μg ml −1 for octyl dimethyl PABA, 0.1 μg ml −1 for methylbenzylidene camphor and 0.05 μg ml −1 for butyl methoxydibenzoylmethane. The half-lives calculated indicate a very good photostability of the sunscreens studied and permit to classify amongst themselves.