HPLC Determination of Tranexamic Acid in Whitening Freckle Cosmetics

HPLC was applied to the determination of tranexamic acid in whitening freckle cosmetics. The sample (0.500 0 g) was extracted ultrasonically with 20 mL of mixture of saturated sodium chloride solution and methanol (1+1) for 5 min. After centrifugation,the supernatant was evaporated to near dryness by N₂-blowing at 45℃ in a water bath. 1 g·L^-1 dansyl chloride solution (500 μL) and 100 mmol·L^-1 NaHCO₃ solution (500 μL) were added to bring derivatization reaction for 5 min. After cooling, the solution was filtered on 0.22 μm microporous membrane. Zorbax SB C₁₈ chromatographic column was used as stationary phase, and the mixed solution of acetonitrile and 0.1% (φ) formic acid solution mixed in different ratios was used as mobile phase in gradient elution. Detection at 250 nm was adopted in the determination. Linear relationship between values of peak area and mass concentration of tranexamic acid was kept in the range of 1.0-100.0 mg·L^-1, with detection limit (3S/N) of 0.3 mg·kg^-1. The proposed method was applied to the analysis of samples of whitening freckle cosmetics, giving values of recovery and RSDs (n=6) in the ranges of 90.8%-98.0% and 2.0%-2.8% respectively.