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

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 PAPA, 4-methylbenzylidene camphor and butyl methoxydibenzoylmethane, at levels in the range of 25-60 mu 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 mu g ml(-1) for benzophenone-3, 1 mu g ml(-1) for PEG-25 PAPA, 0.15 mu g ml(-1) for octyl dimethyl PAPA, 0.1 mu g ml(-1) for methylbenzylidene camphor and 0.05 mu g ml(-1) for butyl methoxydibenzoylmethane. The half-lives calculated indicate a very good photostability of the sunscreens studied and permit to classify amongst themselves. (C) 1999 Elsevier Science B.V. All rights reserved.