Simultaneous Determination of Magnesium L-Ascorbyl-2-Phosphate and Kojic Acid in Cosmetic Bleaching Products by Using a Microbore Column and Ion-Pair Liquid Chromatography

A rapid, sensitive, and reliable method was developed for the simultaneous determination of magnesium L-ascorbyl-2-phosphate (AS-PM) and kojic acid (KA), commonly using bleaching agents in cosmetic products. The method uses a prepacked C18 microbore column for ion-pair liquid chromatography with photodiode array detection. The eluant is 0.5mM tetrabutylammonium bromide and 0.05M phosphate buffer, pH 5, containing 5% methanol, at a flow rate of 70 μL/min. The determinations of AS-PM and KA were linear in the range of 0.5–1000 and 0.25–500 ng, respectively.The precision of the assay ranged from 0.31 to 2.19%, and the detection limits (signal-to-noise ratio = 3) were 0.04 and 0.02 ng for AS-PM and KA, respectively.