Optimized Separation Method for Estriol, 17-β-Estradiol and Progesterone by Capillary Electrochromatography with Monolithic Column and its Application to a Transdermal Emulsion

A monolithic stationary phase based on 3-(methacryloxypropyl)trimethoxysilane monomer, prepared within a fused silica capillary externally coated with a UV-transparent fluoropolymer was employed for separation of estriol, 17-b-estradiol and progesterone by capillary electrochromatography in a standard mixture. A 23 factorial design was used to optimize the separation system. The optimized condition containing 30% (v/v) of acetonitrile and 10 mmol L-1 aqueous ammonium acetate presented a total run time less than 10 min by applying 25 kV. The resolution between adjacent peaks ranged from 1.8 up to 2.9 and the plate numbers per column meter in this condition was 1873, 3631 and 3886 for the estriol, 17-b-estradiol and progesterone peaks, respectively. The optimized method was employed in the quantitative analysis of a commercial transdermal emulsion formulation.