Dynamic on-column eluent modification: A novel strategy for peak resolution enhancement. Application to the preparative separation of ecdysteroid isomers

摘要

A novel LC method was applied to enhance the peak resolution of two ecdysteroids: 20-hydroxyecdysone and its 3-epimer. An isocratic solvent system of methanol-water (6:4, v/v) was used on a C18 column, and 100 mu L of water was injected during the development in such a manner that the eluted solvent peak appeared exactly between the two overlapping peaks. This resulted in the increased retardation of the later-eluted peak, and in a good separation of the two compounds within 4.5 min.