Determination of seven preservatives in cosmetic products by micellar electrokinetic chromatography

A micellar electrokinetic chromatography method using cetyltrimethylammonium bromide (CTAB) as a cationic surfactant, coupled with UV-Vis detection, was developed for the simultaneous determination of seven preservatives, including methyl-, ethyl-, propyl- and butyl-paraben and phenol, phenoxyethanol and resorcinol. The method involved optimizing the pH of the phosphate buffer and concentrations of CTAB, ethanol and 2-hydroxypropyl--cyclodextrin (HP--CD). The preservatives were well separated using optimum conditions and separated within 10min at a separation voltage of -12.5 kV with the 1.0 mM phosphate buffer (pH 7.0) containing 90 mM CTAB, 25 mM HP--CD and 10% (v/v) ethanol. Satisfactory recoveries (84.1-103.0%), migration time (RSD < 3.1%) and peak area (RSD < 4.5%) repeatabilities were achieved. Detection limits of the preservatives were between 0.31 and 1.52g mL(-1) (S/N=3, n=5). The optimized method was successfully applied to the simultaneous determination of these preservatives in 10 commercial cosmetic products.