Determination of parabens in cosmetics without previous extraction by micellar liquid chromatography

A simple and rapid micellar liquid chromatography method for the determination of p-hydroxybenzoic acid esters (methyl-, ethyl-, n-propyl-, and n-butylparaben) in cosmetics (bath foam, milk lotion, hand cream, cream base, and shampoo) is described. The samples are solved with n-propanol, further diluted with more n-propanol or with an aqueous sodium dodecyl sulphate (SDS) micellar solution, and injected. Separations are performed with a micellar mobile phase containing 0.1M SDS, 2.5% n-propanol, 10mM phosphate (pH 3), and with an octadecyl silica column (C18). Calibrations are linear (correlation coefficient r > 0.999) and the limits of detection range from 0.03 to 0.3 ng paraben. The determination of parabens at concentrations well below the levels used in cosmetic formulations is possible. Repeatabilities range from 0.2 to 1.1% for 35 ng paraben.