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Rapid Comparison of UVB Absorption Effectiveness of Various Sunscreens by UV-Vis Spectroscopy

Ju Chou, Ted J. Robinson and Hui Doan

Sunscreens are used to absorb or block harmful sunlight especially ultra violet (UV) radiation. An UV-vis spectrometer was employed to measure absorbance of sunscreen products. The same brand’s sunscreens with sun protection factor (SPF) of 8, 15, 30, and 50 were tested under identical experimental conditions. The results show that the UV absorbance and the transmittance of the sunscreens are associated with the SPF value. The maximum absorbance of the sunscreens measured between 280 to 320 nm (UVB region) is linearly proportional to the SPF value with a correlation coefficient of 0.998 using the same brand’s sunscreens. Thus, the absorbance can be used to evaluate the efficiency of a sunscreen that absorbs or blocks UVB radiation. Several commercial sunscreens of different brands but with the same SPF 30 were compared. The results confirmed that, although different brand sunscreens with the same SPF varied slightly in UV absorbance, they all offer adequate protection against UVB radiation. The utilization of UV-Vis spectroscopy is found to be particularly effective for determination of sunblock efficiency.