JOURNAL OF COSMETIC SCIENCE 172 CONCLUSIONS Determination of OMC in sunscreens was achieved using a UV-spectrophotometric method validated according to ICH and AOAC guidelines (11,12). Methanol was found to be the optimal solvent, with the method showing an analytical linearity range between 4 and 12 μg/ml with a determination coeffi cient of 0.999. Furthermore, the method was applicable to emulsions containing 1%, 4%, and 7.5% of OMC, including those in min- eral oil. Thus, this method is an inexpensive, simple, rapid, accurate, and precise way to determine the OMC content in sunscreen products (5), and could be a viable alternative to HPLC and MECC methods (2,5,7,8). However, this validated method is only suitable for sunscreen products comprising solely OMC as the UV fi lter, without some type of chromatographic separation, any other chemical species with an absorbance in the range of OMC could cause interference and might lead to erroneous results. The challenge is to expand the scope of this method for the detection of different suncare actives and for use in other formulations to enhance its potential quality assurance applications in the phar- maceutical industry. ACKNOWLEDGMENTS Mae Fah Luang University is acknowledged for facilities support and the manuscript preparation. REFERENCES (1) E. Gilbert, F. Pirot, V. Bertholle, L. Roussel, F. Falson, and K. Padois, Commonly used UV fi lter toxic- ity on biological functions: Review of last decade studies, Int. J. Cosmet. Sci., 35, 208–209 (2013). (2) P. Kullavanijaya and H. W. Lim, Photoprotection, J. Am. Acad. Dermatol., 52, 937–958 (2005). (3) K. Jung, M. Seifert, Th. Herrling, and J. Fuchs, UV-generated free radicals (FR) in skin: Their preven- tion by sunscreens and their induction by self-tanning agents, Spectrochim. Acta A., 69, 1423–1428 (2008). (4) A. O. Barel, M. Pay, and H. I. Maibach, Handbook of Cosmetic Science and Technology, 3rd Ed. (Informa Healthcare, New York, NY, 2009). (5) J. Cheng, Y.-L. Li, R. L. Roberts, and G. Walker, Analysis of 2-ethylhexyl-p methoxycinnamate in sun- screen products by HPLC and Raman spectroscopy, Talanta, 44, 1807–1813 (1997). (6) Y. Shih and F.-C. Cheng, Determination of sunscreen agents in cosmetic products using microwave- assisted extraction and liquid chromatography, J. Chromatogr. A., 876, 243–246 (2000). Table V Repeatability of the Analytical System Preparation OMC (%) SPF Recovery ± RSD (%) O/W emulsion 1 2.83 ± 0.11 96.08 ± 0.14 4 5.12 ± 0.79 98.50 ± 0.08 7.5 8.27 ± 0.59 97.23 ± 0.29 W/O emulsion 1 2.18 ± 0.43 99.06 ± 0.10 4 6.30 ± 0.48 97.56 ± 0.16 7.5 8.28 ± 0.90 99.11 ± 0.17 Mineral oil 1 2.50 ± 0.22 98.25 ± 0.50 4 6.29 ± 0.62 98.01 ± 0.10 7.5 8.65 ± 0.76 99.27 ± 0.19

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