High-Speed Liquid Chromatographic Separation of Equine Estrogens

The high-speed liquid chromatographic separation of nine equine estrogens, including estrone and equilin, is reported. Four partition systems using β,β-oxydipropionitrile, cyanoethylsilicone, ethylene glycol, and a mixture of β,β-oxydipropionitrile and ethylene glycol, as stationary phases were investigated. Two “permanently-bonded” packing materials, ODS- and ETH-Permaphase, were also included in the study. The sulfate esters of many of the estrogens studied are components of commercial conjugated estrogen formulations. The separation achieved on a 3 meter ETH-Permaphase column at 40°C using a mobile phase of 2% v/v tetrahydrofuran in n-hexane provides a basis for the analysis of these formulations.