Method for screening sunscreen cream formulations by determination of in vitro SPF and PA values using UV...

Formulation of sunscreen products to obtain high values of sun protection factor (SPF) and protection from ultraviolet A (PA) is challenging work for cosmetic chemists. This study aimed to study factors affecting SPF and PA values using ultraviolet transmission spectroscopy as well as texture profiles of sunscreen formulations using 23 factorial designs. Results demonstrate that the correlation coefficient between the labeled SPF values of counter-brand sunscreen products and the in vitro SPF values was 0.901. In vitro SPF determination showed that the combination effect of phase volume ratio (PVR) and xanthan gum caused a significant increase to the SPF values of the formulations, whereas the interaction effect between PVR and stearic acid significantly decreased the SPF value. In addition, there was the interaction effect between xanthan gum and stearic acid leading to significant reduction of hardness, compressibility, and pH, but significantly increasing the adhesiveness. All tested factors did not significantly affect the cohesiveness of tested formulations. In conclusion, apart from sunscreen agents, the other ingredients also affected the SPF and PA values. The calculated SPF values range from 21 to 60. However, a selected formulation needs to be confirmed by the standard method of testing. In addition, the physical, chemical, and biological stability; shelf life; and sensory evaluation of all formulations need to be evaluated.