Simultaneous determination of magnesium ascorbyl phosphate, ascorbyl glucoside, kojic acid, arbutin and hydroquinone in skin whitening cosmetics by HPLC

A high performance liquid chromatographic method was developed for simultaneous determination of 5 whitening ingredients: magnesium ascorbyl phosphate, ascorbyl glucoside, kojic acid, arbutin and hydroquinone decomposed from arbutin in cosmetics. Samples were extracted with 0.05 M KH2PO4 buffer solution (pH 2.5) and analyzed using a Cosmosil 5 C18-AR-II column. A mixture of 0.05 M KH2PO4 buffer solution (pH 2.5) and methanol (99:1, v/v) was used as mobile phase. The UV detector was set at 280 nm. Pyridoxine was used as an internal standard. The related coefficients, R2, of regression equations of the 5 standard curves were 0.9998-1.0000. The relative standard deviations of the 5 ingredients for intraday and interday analysis were less than 2.4%. The average recoveries of these 5 ingredients spiked in sample ranged from 93.5% to 103.3%. The relative standard deviations of average recoveries were less than 1.3%. The limits of quantitation in cosmetics were 80.0, 20.0, 3.0, 15.0 and 10.0 μg/mL for magnesium ascorbyl phosphate, ascorbyl glucoside, kojic acid, arbutin and hydroquinone, respectively.