Determination of 3 Corticosteroids in Cosmetics by Field Amplified Sample Introduction-Micellar Capillary Electrophoresis

Micellar capillary electrophoresis with field amplified sample introduction was applied to the separation and determination of 3 corticosteroids, including hydrocortisone, prednisone and hydrocortisone acetate, in cosmetics. The optimized conditions were shown as follows: ① electrophoretic medium: 0.20 mmol·L-1 borax buffer solution of pH 9.0; ② conveying voltage: -20 kV; ③ sample injection voltage: -20 kV; ④ time of sample injection: 45 s; ⑤ pressure of water-intake: 3 kPa; ⑥ time of water-intake: 20 s; ⑦ detection wavelength: 250 nm. Values of detection limits (3S/N) for hydrocortisone, prednisone and hydrocortisone acetate found were 0.015, 0.017, 0.017 mg·L-1 respectively. The proposed method was used in the analysis of cosmetics sample, giving values of recovery in the range of 93.8%-107% with RSD′s (n=5) less than 5.1%.