DETERMINATION OF SUN PROTECTION FACTOR (SPF) OF SUNSCREENS BY ULTRAVIOLET SPECTROPHOTOMETRY

MAURENZI, DAIANA ROCÍO; NUÑEZ, MARÍA BEATRIZ; TORRES, CAROLA ANALÍA

Rosario

Encuentro; 4ª Reunión Internacional de Ciencias Farmacéuticas; 2016

The efficacy of a sunscreen is usually expressed by the sun protection factor (SPF), which is defined as the UV energy required producing a minimal erythema dose (MED) on protected skin, divided by the UV energy required to produce a MED on unprotected skin. The aim of this research was to determine the sun protection factor (SPF) of sunscreen formulations by ultraviolet spectrophotometry. The method selected was proposed by Mansur et al. (1986). The solutions (1%) of the samples were prepared, a 5.0 mL aliquot was transferred to 50 mL volumetric flask and diluted to volume with ethanol. Then a 5.0 mL aliquot was transferred to a 25 mL volumetric flask and the volume completed with ethanol. These solutions were read in triplicate and the readings were made at 290?320 nm. Ethanol was used as blank. Ten different commercial samples of sunscreen products were evaluated. The SPF labeled values were in the range of 2 to 60. The SPF values of five of the analyzed samples (1, 2, 4-6) are in close agreement with the labeled SPF, whereas five (3, 7-10) presented a minor amount of the declared. These data variations can be due to the type of formulations, the interactions of vehicle components, the pH of the system, the emulsion rheological properties or the use of different solvents in which the sunscreens are dissolved. However, this spectrophotometric method could be useful as pre-screening and predictive tool prior to the in-vivo test when optimizing the formulation with new sunscreen ingredients or changing their compositions. This method can be used as a rapid quality control method during the manufacturing processes.