Mixed-mode HPLC aplication of a newly developed stationary phase basen on [2-(3,4-epoksisiklohekzil) etil]trimetoksisilan

A new silica-based mixed-mode stationary phase derived from [2-(3,4-epoxycyclohexyl)ethyl]trimethoxysilane as a coupling reagent was synthesised and evaluated for hydrophilic interaction/reversed-phase high-performance liquid chromatography (HPLC). The new stationary phase bearing polar amide, amine and alcohol groups as well as nonpolar aliphatic and aromatic groups was synthesised starting from [2-(3,4-epoxycyclohexyl)ethyl]trimethoxysilane and isoleucine amino acid and characterized by elemental analysis, infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and solid-state 13C nuclear magnetic resonance (CPMAS NMR). Several aromatic compounds having different polarities were tested for hydrophilic interaction liquid chromatography (HILIC) and reversed phase (RP) condition and successful separation could be achieved. Water soluble vitamins and nucleobases were tested to investigate effectiveness of the new column on HILIC mode. The six water soluble vitamins separated successfully by a gradient elution, and five nucleobases were separated by an isocratic elution. A number of moderately and weakly polar and nonpolar small compounds such as substituted benzoic acids, chlorinated herbicides, alkyl benzenes and a mixtures of polar/nonpolar aromatic compounds were tested for the RP condition and separated successfully. The retention factor, theoretical plate number and peak asymmetry factor were calculated for all of the analytes separated by isocratic elution. Compared to traditional C18 and commercial HILIC columns, the new stationary phase exhibited both HILIC and RPLC performance, and the scope of analyte separation was thus enlarged.