Environmentally friendly LC for the simultaneous determination of ascorbic acid and its derivatives in skin-whitening cosmetics

Ascorbic acid (AA), also known as vitamin C, is a very popular skin-whitening agent used in cosmetics. However, the use of AA (and also its sodium or magnesium salts) in cosmetic products is limited owing to its labile oxidative properties. In order to avoid its early degradation, different derivatives have been designed, such as ascorbyl phosphate (APH; as magnesium or sodium salts) and ascorbyl palmitate (AP), and more recently the ascorbyl glucoside (AG). Bearing in mind that all these chemicals in skin-whitening cosmetic products must be determined in order to control the efficacy of such products, this paper focuses on developing a wide-ranging LC analytical method able to determine the above-mentioned compounds simultaneously in cosmetic products. The chromatographic variables were studied and selected in order to achieve the total separation and subsequent determination of all the analytes involved. Thus, an octadecylsilica (C(18)) stationary phase and a mobile phase gradient of ethanol: 50 mM phosphate buffer at different pHs (containing 0.1 M NaCl) were used. Detection was carried out with a UV/visible spectrometry detector set at different wavelengths. The LOD ranged from 2 to 6 microg/mL depending on the analyte. The proposed method was validated by analysing a laboratory-made and six commercial skin-whitening cosmetic samples. The method allows any mixture of the four skin-whitening agents studied to be both separated at good resolution and determined without interferences from samples, and moreover it does not require the use of either highly toxic organic solvents or hazardous chemicals.