470 JOURNAL OF COSMETIC SCIENCE According to the manufacturer's reference (Ciba), a UV-A filter (methylene bis­ benzotriazolyl tetramethyl butylphenol) is a highly efficient sunscreen due to its triple action: UV absorption by a photostable organic molecule, light scattering, and light reflection by its microfine structure. Methylene bis-benzotriazolyl tetramethyl butyl­ phenol in this research is micronized powder containing more than 98.5% of the active entity. Methylene bis-benzotriazolyl tetramethyl butylphenol has been proven to be extremely photostable. It has synergistic and stabilizing effects when combined with other organic sunscreen agents. Secondly, bis-ethylhexyloxy phenol methoxyphenyl triazine is a full-spectrum UV(A+B) filter. It has high inherent photostability and also has two distinctive absorption bands with different polarization directions and extinction coefficients (UV-A/UV-B). It has been optimized for efficient dissipation of UV radiation to harmless thermal energy. This shows that methylene bis-benzotriazolyl tetramethyl butylphenol and bis­ ethylhexyloxy phenol methoxyphenyl triazine function as effective sunscreens. Due to their strong sunscreening effect, methylene bis-benzotriazolyl tetramethyl butylphenol and bis-ethylhexyloxy phenol methoxyphenyl triazine have been used in many suncare products as UV-A filters. Thin-layer chromatography (TLC) (5 ), high-performance liquid chromatography (HPLC) (6-11), and gas-liquid chromatography (GC) (12) have been used for determi­ nation of the sunscreen agents in suncare products. In spite of high utilization of the chromatographic systems, never before has there been literature reporting the effects of the simultaneous determination method of methylene bis-benzotriazolyl tetramethyl butylphenol and bis-ethylhexyloxy phenol methoxyphenyl triazine with hydrophilic UV-B filters (13,14). We have proposed a new determination method based on HPLC and UPLC for the simultaneous assay of methylene bis-benzotriazolyl tetramethyl butylphenol, bis­ ethylhexyloxy phenol methoxyphenyl triazine, ethylhexyl methoxycinnamate, isoamyl p-methoxycinnamate, ethylhexyl salicylate, and ethylhexyl triazone in suncare products. The proposed method is simplified and is reproducible. It can determine UV-A filters, which normally use extremely hydrophobic compounds such as methylene bis­ benzotriazolyl tetramethyl butylphenol and bis-ethylhexyloxy phenol methoxyphenyl triazine, with hydrophilic UV-B filters in a single run. The method is suitable for quality control of the assays of sunscreen agents in suncare products and cosmetics as it can provide a fast and efficient separation of the UV filters. See Figure 1 for the chemical structures of the six sunscreen agents examined in this study. MATERIALS AND METHODS Suncare products for validation of accuracy were prepared by Amore-Pacific (Gyeonggi­ do, Korea). Ten suncare products were purchased in Seoul in October 2006. INSTRUMENTATION The HPLC used in the test was the Waters Alliance system (Waters, Milford, MA). The system consisted of a 2996 FDA detector, a pump, an autosampler, and a column oven,

DETERMINATION OF SUNSCREEN AGENTS BY UPLC AND HPLC 471 Ethylhexyl Methoxycinnamate (OMC) OH � C-OCH2 I H(CH2hCH3 CH2CH3 # Ethylhexyl Salicylate (OS) lsoamyl p-Methoxycinnamate (Th1C) � �NOH I N-N Methylene Bis-Benzotriazolyl -Tetramethylbutylphenol(TM) Ethylhexyl Triazone(OT) Bis-Ethylhexyloxyphenol -Methoxyphenyl Triazine(TS) Figure 1. Chemical structures of OMC, IMC, OS, OT, TM, and TS. which enabled temperature control of the analytical column. Analytical data was col­ lected and processed by the system's own chromatographic software, Empower II. The column used was a Waters Symmetry ClS column (4.6 mm x 75 mm, 3.5 µm).