Sayre Robert M, Dowdy John C, Gerwig Andre J, Shields William J, Lloyd Roger V
Rapid Precision Testing Laboratories, Cordova, TN 38016, USA.
Photochem Photobiol. 2005 Mar-Apr;81(2):452-6. doi: 10.1562/2004-02-12-ra-083.1.
A major concern raised about photostability studies of sunscreen products is that the photodegradation of sunscreens does not readily translate into changes in product performance. This study examines the correlation between photochemical degradation of sunscreen agents and changes in protection provided by sunscreen films. Films of a commercial sunscreen product containing avobenzone, oxybenzone and octinoxate were irradiated using a fluorescent UV-A phototherapy lamp with additional UV-B blocking filter. Periodically, during irradiation the transmittances of the films were measured and samples collected for chemical analysis of the sunscreen agents using high-performance liquid chromatography techniques. The results show that UV-induced changes in UV transmittance of sunscreen films correlate with changes in concentration of sunscreen agents. In a parallel experiment, we also irradiated a thin film of the same product in the cavity of an electron spin resonance (ESR) spectrometer. We report the concomitant photolysis of avobenzone and octinoxate that predominates over expected E/Z photoisomerization and that irradiation of a film of this product produced free radicals detected by ESR spectroscopy that persisted even after exposure had ended.
关于防晒产品光稳定性研究引发的一个主要担忧是，防晒剂的光降解并不能轻易转化为产品性能的变化。本研究考察了防晒剂的光化学降解与防晒膜防护效果变化之间的相关性。使用配备额外紫外线B阻挡滤光片的荧光紫外线A光疗灯，对含有阿伏苯宗、二苯甲酰甲烷和桂皮酸盐的市售防晒产品薄膜进行照射。在照射过程中，定期测量薄膜的透光率，并采集样品，使用高效液相色谱技术对防晒剂进行化学分析。结果表明，紫外线引起的防晒膜紫外线透光率变化与防晒剂浓度变化相关。在一项平行实验中，我们还在电子自旋共振（ESR）光谱仪的样品腔中对同一产品的薄膜进行了照射。我们报告了阿伏苯宗和桂皮酸盐的伴随光解，其占主导地位，超过了预期的E/Z光异构化，并且该产品薄膜的照射产生了可通过ESR光谱检测到的自由基，即使在照射结束后这些自由基仍持续存在。
