Affiliation: Institute of Chemistry, University of São Paulo, Av. Prof. Lineu Prestes 748, 05508-000 São Paulo, SP, Brazil.
A rapid and simple microemulsion electrokinetic chromatography (MEEKC) method has been developed and validated for the determination of ethinylestradiol and levo-norgestrel in a commercial tablet formulation. The analysis was performed with an electrolyte composed of 0.5% (w/w) ethyl acetate, 1.2% (w/w) butan-1-ol, 0.6% (w/w) sodium dodecyl sulfate, 15% (v/v) ethanol and 82.7% (w/w) 12 mmol L−1 sodium tetraborate aqueous buffer at pH 9.23 and direct UV detection at 200 and 247 nm. For quantitative purposes, estrone was used as an internal standard. Retention time for levo-norgestrel and ethinylestradiol was approximately 2.1 and 2.5 min respectively. Acceptable precision (<0.90% RSD, linearity (r2 > 0.99; concentration range from 24.0 to 36.0 µg mL−1), limits of detection (LOD) and quatification (LOQ) for ethinylestradiol of 1.0 μg mL-1 and 3.2 µg mL−1, respectively, and for levo-norgestrel of 1.4 µg mL−1 and 4.1 µg mL-1, respectively, and recovery of 100 ± 2 % at three concentration levels were obtained. Based on the performance characteristics, the proposed methodology was found suitable for the determination of ethinylestradiol and levo-norgestrel in tablet formulations.