High-Performance Liquid Chromatographic Separation of Equilin, Estrone, and Estrone Derivatives with Cyclodextrins as Mobile Phase Additives

Abstract

β-Cyclodextrin and two derivatized β-cyclodextrins were utilized as mobile phase additives for the liquid chromatographic resolution of equilin and estrone, as well as estrone from 2-hydroxyestrone, 4-hydroxyestrone, and 16α-hydroxyestrone on a C₁₈ stationary phase. β-Cyclodextrin proved to be suitable for the separations of these steroids but the modified β-cyclo-dextrin provided better resolution. A comparison was made of the separation and retention obtained with β-cyclodextrin with that of the modified β-cyclodextrins. Apparent inclusion complex strengths for estrone and its derivatives with each cyclodextrin were calculated. The effects of mobile phase cyclodextrin concentration and methanol content on selectivity and capacity factor were examined.