title: First-derivative spectroscopic determination of sunscreens in cosmetic formulations.
abstract: Summary Nowadays, cosmetic as well as pharmaceutical forms must undergo many controls, i.e. in-process controls on the finished product and stability testing. The authors suggest using first derivative spectroscopy for active ingredients assay presenting an ultra-violet absorption. It offers the advantage of a direct assay through simple dilution and without active ingredient extraction. Tests were made on classic mixtures of the sunscreens benzimidazol and cinnamate derivative (pair 1), and a mixture of two benzophenones (pair 2). The studied forms were solutions in propylene glycol and commercialized W/O and O/W creams. After analytical method validation for each sunscreen by precision, reproducibility and repeatability studies, the percentages of error of the various assays have been reported in various preparations (solutions or creams). A comparative study between HPLC assay (traditionally used) and the proposed method was carried out. The results show that a highly significant linear correlation exists between the two methods for the four sunscreens (R > 0.992). The speed and simplicity of the first derivative spectrometric method should find applications in routine control or in development of cosmetic or pharmaceutical preparations.
authors.affiliation: Faculté des Sciences Pharmaceutiques, Laboratoire de Pharmacie Galénique, 35 Chemin des Maraîchers 31400 Toulouse and.
authors.forename: P
authors.initials: P
authors.lastname: Michaud
authors.forename: P
authors.initials: P
authors.lastname: Soto
authors.forename: T L
authors.initials: TL
authors.lastname: Roy
authors.forename: F
authors.initials: F
authors.lastname: Rodriguez