Synthesis and performance of chiral ferrocene modified silica gel for mixed-mode chromatography.

A brush-type chiral stationary phase, N-ferrocenyl benzoyl-(1S, 2R)-1, 2-diphenyl ethanol-bonded on the silica gel (NFcBEs) for high performance liquid chromatography (HPLC), was prepared using γ-glycidoxypropyltrimethoxysilane as coupling reagent. The structure of this novel material was characterized by infrared spectroscopy, elemental analysis and thermogravimetric analysis. Mechanism involved in the chromatographic separation is the multi-interaction including hydrophobic, π-π, hydrogen-bonding, π-charge transfer, dipole-dipole and acid-base equilibrium interactions. Based on these interactions, successful separation could be achieved among polycyclic aromatic hydrocarbons, mono-substituted benzenes, aromatic amines, quinolines, nucleosides, phenols and 5-nitroimidazoles drugs in reversed phase liquid chromatography (RPLC). Good resolutions for substituted amine isomers were also obtained with NFcBEs. Racemates of amino acids and drug carvedilol mixtures were well separated on NFcBEs in the normal phase liquid chromatography (NPLC) mode. Such stationary phase with characteristics of multi-interaction mechanism and mixed-mode separation is potential for the analysis of complex samples. The retention behaviors of R- and S-carvedilol on NFcBEs column were investigated with the assistance of quantum chemistry calculation using the density functional theory (DFT) B3LYP method.