Abstract
A rapid and reliable method based on micellar electrokinetic capillary chromatography has been developed for the determination of dexamethasone in cosmetics. Effects of buffer composition, concentration and pH, the detection wavelength, separation voltage, and injection time were systematically investigated. The optimum conditions were: 30 mM borax buffer containing 20 mM sodium dodecyl sulfate at pH 9.0, detection at 254 nm, injection time 10 s at a height of 10 cm, and a separation voltage of 15 kV. Under these conditions, the analysis of dexamethasone in cosmetics was carried out within 6 min. The method was validated for stability, precision, linearity and accuracy. Excellent linearity was obtained in the range of 50–1,000 μg mL−1, and acceptable precision, in intra-day and inter-day analysis, was also obtained with relative standard deviation in the range of 0.19–0.86 and 2.50–4.90% for migration time and peak area ratio, respectively. The method was used to analyse eight cosmetic samples purchased locally.
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