UVA/UVB sunscreen determination by second-order derivative ultraviolet spectrophotometry

• Published in: Farmaco (Società chimica italiana : 1989) 1999-09, Vol.54 (9), p.573-578
• Main Authors: Azevedo, Jacqueline S, Viana, Nilton S, Vianna Soares, Cristina D
• Format: Article
• Language: English
• Subjects: Applied sciences; Benzimidazoles - chemistry; Benzophenones - chemistry; Chemical industry and chemicals; Cosmetics determination; Cosmetics, toiletries; Exact sciences and technology; Second-order derivative; Spectrophotometry, Ultraviolet; Sulfonic Acids; Sunscreening Agents - chemistry; Ultraviolet Rays; Ultraviolet spectrophotometry; UVA/UVB sunscreen; Washing products. Cosmetics and toiletries. Perfumes
• ISSN: 0014-827X; 1879-0569
• DOI: 10.1016/S0014-827X(99)00063-4

UVA/UVB protective agents are important constituents in many cosmetics and sunscreen preparations. Analytical methodologies which enable the determination of combined substances with different spectrophotometric characteristics are therefore useful and cost-effective. To this end, the following substances in a sunscreen gel were analyzed: the UVB and UVA protective substances, 2-hydroxy-4-methoxy-benzophenone-5-sulphonic acid (BZP) and 2-phenylbenzymidazole-5-sulphonic acid (PBS), respectively, were evaluated by second-order derivative ultraviolet spectrophotometry in distinct solvents and wavelengths. The method used for determination of BZP in 95% ethanol was the zero-peak (ZP) at 356.0 nm. For PBS, the solvent used was 0.1 mol l −1 triethanolamine, and the methods were the ZP at 317.5 nm and the peak-peak (PP) at 317.5–323.0 nm. Statistical results for the methods showed linearity of 0.9999 and an average precision of 1.12% (ZP) for BZP, and 0.55% (ZP) and 0.63% (PP) for PBS. The average recovery for BZP and PBS were 97.28% (ZP), 103.13% (ZP) and 103.71% (PP), respectively.