Ergot alkaloids as chiral selectors in capillary electrophoresis determination of the separation mechanism

Abstract

Recently ergot alkaloids were introduced as novel chiral selectors in capillary electrophoresis. In the present study, stereoselectivities of several ergot alkaloids, added to the background electrolyte (BGE), towards some racemic hydroxy organic acids are compared. The 1-allyl derivative of (5 R,8 S,10 R)-terguride (allyl-TER) proved to be the best chiral selector for these analytes. Only the capillary was filled with BGE containing the chiral selector. The in- and outlet vial did not contain any ergot alkaloid. The effects of pH, and MeOH added to the BGE were investigated. Low pH proved to have an adverse effect on enantioseparation. Good separation for the enantiomers of some α-hydroxy acids was obtained at pH 4.2, and 25 m M allyl-TER. The addition of 50% MeOH to the BGE altered stereoselectivity and increased the solubility of the chiral selector. Using a BGE containing 50% MeOH, and 62.5 m M allyl-TERat pH ∗ 5.5, the optical isomers of all test compounds, including tropic acid and other organic acids, were baseline resolved.