Simultaneous Determination of Phenolic Additives in Cosmetics by Micellar Electrokinetic Capillary Chromatography with Electrochemical Detection

A micellar electrokinetic capillary chromatography method with electrochemical detection (MECC-ED) has been developed for the simultaneous determination of eight phenolic additives, including propyl gallate (PG), tert-butylhydroquinone (TBHQ), butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), methylparaben (MP), ethylparaben (EP), propylparaben (PP) and butylparaben (BP) in cosmetic products. Method development involved optimization of the working electrode, the pH value of running buffer, the concentration of sodium dodecyl sulfate (SIDS), the separation voltage, and the sample injection time. Under the optimum conditions, all analytes can be well separated within 26 min at the separation voltage of 18 kV in a 9 mmol.L-1 sodium dodecyl sulfate (SIDS) -60 mmol.L-1 borate running buffer (pH 8.0). A 300 mu m diameter carbon disk electrode generated good response at +0.90 V (vs. SCE) for all analytes. Linearity of the present method was over three orders of magnitude of analyte concentration with detection limits (S/N=3) ranging from 1.1 X 10(-7) to 1.2 X 10(-6) g.mL(-1) for all analytes. This proposed method has been successfully applied to the simultaneous determination of the above additives in commercial cosmetics, and the assay results were satisfactory.