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 microL/min. The determinations of AS-PM and KA were linear in the range of 0.5-1,000 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.