Abstract: A high performance liquid chromatography (HPLC) was established for the simultaneous determination of urocanic acid and its ethyl ester in sunscreen cosmetics.The result was comfirmed with mass spectrometry.Cosmetic samples were extracted with methanol under assistance of ultrasonic wave and the extract was centrifuged and filtered with a microporous membrane filter.Then the filtrate was transfer for HPLC analysis using an XTerra MS C₁₈ column (4.6 mm×250 mm,5 μm).The mobile phase was a solution composed of methanol and 5 mmol/L tetrabutylammonium bromide (30∶70) with isocratic elution.The column temperature was set at 35 ℃.The flow rate was 1 mL/min and the wavelength of detection was at 285 nm.The quantification was carried out by external standard method.The experimental results indicated that the limits of quantification (LOQs) for urocanic acid and its ethyl ester were both 5 mg/kg.The mean recoveries at three spiked levels ranged from 80.1% to 103.8% with the relative standard deviations (RSD) between 1.2% and 6.9%.The suspected positive samples were subjected to further verification by LC-MS/MS.The method is accurate,rapid,sensitive,and can be used for the inspection of sunscreen cosmetics.

Key words: sunscreen cosmetics, urocanic acid, ethyl urocanate, high performance liquid chromatography