Simultaneous Determination of Five Whitening Agents by Ion-Pair Reversed-Phase High Performance Liquid Chromatography

A gradient ion-air reversed-phase high performance liquid chromatography method was developed for simultaneous determination of 5 whitening agents (ascorbic acid (AA), magnesium ascorbyl phosphate (MAP), kojic acid (KA), arbutin (ART) and hydroquinone (HQ)). The gradient elution was performed using Inertsil ODS-3V column (250 × 4.6 mm, 5 μm). The analytes were detected by ultraviolet light absorption at the wavelength of 270 nm, the flow rate was set at 1.0 mL/min, and the sample injection volume was 10 μL. The buffer solution contains 50 mM sodium phosphate monobasic dihydrate and 2 mM n-hexadecyltrimethyl ammonium bromide at pH 4.5. The precision of the proposed method, expressed as relative standard deviation (RSD) (%), was determined by the analysis of each compound. The RSD range was from 0.23 to 0.55%. The calibration curves were found to be linear in 8.12-40.6 μg/mL (KA), 12.44-62.20 μg/mL (ART), 8.28-41.40 μg/mL (HQ), 8.16-40.80 μg/mL (MAP) and 4.25- 1.80 μg/mL (AA). The correlation coefficient of linear regression analysis (R2) was within the range of 0.9968 - 0.9997. The analytical results were satisfied for these 5 whitening agents. The recoveries ranging from 96.97% to 101.22% for lotion, and from 97.17 to 100.80% for cream, were obtained at both low and high concentrations. The proposed method is suitable for routine analysis of the 5 whitening agents in commercial cosmetic products, or examined the allowable amount of whitening agents for the Department of Health.