Determination of 22 Chemical Sunscreens in Sunscreen Cosmetics by High Performance Liquid Chromatography

A method for determination of 22 chemical sunscreens in sunscreen cosmetics by high performance liquid chromatography (HPLC) was established. The sunscreen cosmetic sample of 0.25 g was swirled in 25 mL of mixed solvent I or mixed solvent II, and was extracted for 30 min by ultrasound. The mixed solvent I was a mixture of methanol containing 0.1% (φ, the same below) phosphoric acid solution and isopropanol at volume ratio of 5:9, which was used to extract No.1-20 chemical sunscreens. The mixed solvent II was a mixture of methanol-isopropanol-0.02 mol·L^-1 ammonium acetate solution (adjusted to pH 5.0 with phosphoric acid) at volume ratio of 5:9:2, which was used to extract p-phenylenemethylbiscamphor sulfonicacid (No.21 chemical sunscreen) and phenyldibenzimidazole tetrasulfonate disodium ester (No.22 chemical sunscreen). The obtained extract of 1 mL was taken, diluted to 10 mL with methanol, and passed through a 0.45 μm filter membrane for HPLC analysis. Agilent ZORBAX SB-C₁₈ column was used as the stationary phase, and the mixture of methanol-isopropanol-0.1% phosphoric acid solution at various volume ratios (for separating No.1-20 chemical sunscreens) and the mixture of methanol-0.02 mol·L^-1 ammonium acetate solution (for separating No.21 and No.22 chemical sunscreens) were used as mobile phases for gradient elution. The detection wavelength of No.21 chemical sunscreen was 340 nm, and that of other chemical sunscreens was 311 nm. As shown by the results, linear relationships between values of peak area and mass concentration of 22 chemical sunscreens were found in definite ranges, with detection limits (3S/N) in the range of 0.000 5%-0.06%. The recovery test was carried out with blank sample as substrate, giving results in the range of 86.9%-113%, with RSDs (n=9) of determined values ranged from 0.10% to 5.6%. The method was applied for determination of 20 batches of sunscreen cosmetics, and 14 chemical sunscreens were detected. The results obtained were consistent with those of the method in Safety and Technical Standards for Cosmetics (2015 Edition).