DETERMINATION OF SUN PROTECTION FACTOR OF SUNSCREENS BY TWO DIFFERENT IN-VITRO METHODS
Abstract
Background. Sunscreens usually protect the skin against harmful effects of sunlight. These products contain two effective physical and chemical components, which protects the skin from sunlight. Sun protection factor (S.P.F) is a critical factor indicating the effect of sunscreen against sunlight.
Methods. To measure S.P.F of sunscreens, various in-vivo and in-vitro methods have been established. In this study, two in-vitro methods were used. In 'Transpore tape' method, sunscreen product was dispersed uniformly on the substrate to obtain a surface coverage of 2mg/cm2 of the product. Transmittance measured spectrophotometerically, and then S.P.F was calculated. In the second method (solvent method) different concentrations of test products were prepared in methanol. The sample's transmittance were measured to evaluate S.P.F.
Results. Results of the first method indicated a good linear relationship between measured S.P.F and the labled S.P.F (r=0.97). Results of the second method indicated that relatively a good relationship exisit between log of measured S.P.F and labled S.P.F (r=0.88).
Discussion. The transport tape method is fairly simple, feasible and importantly the surface of the tape is similar to that of the skin. Although, transport method is not time consuming, it is less accurate than in-vivo methods.
Methods. To measure S.P.F of sunscreens, various in-vivo and in-vitro methods have been established. In this study, two in-vitro methods were used. In 'Transpore tape' method, sunscreen product was dispersed uniformly on the substrate to obtain a surface coverage of 2mg/cm2 of the product. Transmittance measured spectrophotometerically, and then S.P.F was calculated. In the second method (solvent method) different concentrations of test products were prepared in methanol. The sample's transmittance were measured to evaluate S.P.F.
Results. Results of the first method indicated a good linear relationship between measured S.P.F and the labled S.P.F (r=0.97). Results of the second method indicated that relatively a good relationship exisit between log of measured S.P.F and labled S.P.F (r=0.88).
Discussion. The transport tape method is fairly simple, feasible and importantly the surface of the tape is similar to that of the skin. Although, transport method is not time consuming, it is less accurate than in-vivo methods.
Keywords
Sunscreen, Sun protection factor