Comparison of Efficiency of Transpore Method and Dilution Solutions Methods in Determination of Sun Protection Factor of some Trade Sunscreen Preparations

Sunscreen preparations are applied to protect the skin against harmful effects of sunshine. The most determining index for evaluation of these preparations is sun-protection factor (SPF), which reflects the degree of protection against UV light. Numerous in vivo and in vitro methods are employed for assessment. Despite the accuracy of in vivo methods, their expensiveness and time consuming have restricted their routine application at the stage of screening formulations. Therefore, in vitro methods are employed. In the present study, the efficacy of two in vitro methods (transpore and the diluted solutions methods) were compared using four trade preparations (Arden, Rasen, Onagrin and Rexol).Subjects and The first method was performed using a suitable, cheap and widely available substrate called transpore tape. In this method 2 mg/cm2 of each product was uniformly dispersed on the surface of the substrate, and the spectrophotomertic transmittance values in the range of 290 – 400 nm, at 5nm intervals, of prepared films were determined and values SPF were calculated. In the second method, different concentrations of test products were made in methanol and UV transmittance values were measured at the range of 292.5–337.5nm and values SPF were calculated. By plotting the amount of SPF versus each concentration the efficency of the products SPF were compared. The SPF of 2 mg/ml concentration of each product was calculated. In the first method results indicated a good, although incomplete, linear correlation between the measured and labelled (r = 0.975). In the second method all resulte were considerably larger than the labelled values and showed poor correlation (r = 0.35). Based on the results, because of the ease of process, availableness and also offering closer result with the in vivo mehtods. the transpore method, in contrast to the diluted solutions method, is a more efficient method for determination of SPF values. Therefore this method can be applied as an in–process control test to ensure lot-to-lot uniformity.