Separation of estrogens by micellar electrokinetic chromatography

Abstract

Capillary electrophoresis of the sex hormone estrogens using different buffer components was investigated. Free zone electrophoresis with 10 m M phosphate buffer (pH 11.5) or 10 m M phosphate buffer with 10–20% methanol was not effective in separating the ten estrogens used in this study. However, nine estrogens were resolved by micellar electrokinetic chromatography using a 10 m M borate buffer (pH 9.2) containing 100 m M sodium cholate. In addition, some estrogens were partially separated using sodium dodecyl sulfate (SDS) micellar buffers; however, the addition of modifiers such as organic solvents or cyclodextrins improved resolutions significantly. Using a 10 m M phosphate buffer (pH 7.0) containing 50 m M SDS and 20% methanol, or a 10 m M borate buffer (pH 9.2) containing 50 m M SDS and 20 m M γ-cyclodextrin, all ten of the tested estrogens were separated. However, the cyclodextrin-modified buffer allowed faster separation.