Simultaneous HPLC determination of hydrophilic whitening agents in cosmetic products.

A high-performance liquid chromatographic method for quantifying four of the most common used hydrophilic whitening agent--glycolic acid (GA), ascorbic acid (AA), arbutin (ART) and Mg ascorbyl phosphate (MAP), has been developed. Isocratic separation was performed using a C18 column with ion-pair agent as mobile phase. The analytes were detected by ultraviolet light absorption at the wavelength of 220 and 240 nm, respectively. Calibration curves were found to be linear in the 8.0-36 mg/ml (GA), 10.0-300 microg/ml (AA and ART), and 5.6-451 microg/ml (MAP). The correlation coefficient of linear regression analysis were with the range 0.9974-0.9997. Recoveries of the four analytes were between 94.8 and 100.1% and the precision of this method was better than 6.9% relative standard deviation (R.S.D.) (n=3). It was found that AA degraded in an aqueous solution. To be sure that AA was stable during the HPLC analysis, all analytes were dissolved in distilled water and these solutions were purged with nitrogen gas to remove oxygen and stored at 25 degrees C. The testing results show that the procedure is rapid, simple, selective method and it is suitable for routine analysis of commercial cosmetics.