A New Mixed‐Mode Stationary Phase Derived from [2‐(3,4‐epoxycyclohexyl)ethyl]trimethoxysilane as a Coupling Reagent and Its RPLC/HILIC/IEC Applications

Abstract A new mixed‐mode stationary phase derived from [2‐(3,4‐epoxycyclohexyl)ethyl]trimethoxysilane as a coupling reagent was synthesized and evaluated for hydrophilic‐interaction/reversed‐phase/ion‐exchange HPLC. This phase bearing polar groups as well as nonpolar aliphatic and aromatic groups was synthesized starting from [2‐(3,4‐epoxycyclohexyl)ethyl]trimethoxysilane and isoleucine amino acid, and it was characterized by elemental analysis, FTIR spectroscopy, SEM, and solid‐state 13 C NMR. The new stationary phase offers hydrophilic interaction, reversed‐phase and ion‐exchange functionalities, which facilitate the simultaneous separation of polar, nonpolar, and ionic compounds. Several polar nonpolar compounds were tested to investigate the retention properties of the new phase. Seven water‐soluble vitamins and five nucleobases/nucleosides were tested to investigate the effectiveness of the new phase in HILIC mode. Six water‐soluble vitamins were separated successfully by gradient elution and the five nucleobases/nucleosides were separated by isocratic elution. Numerous polar and nonpolar small compounds were tested under RPLC conditions, while six selected benzoic acids were tested for the IEC properties of the new phase, and these were also separated successfully. Quantitative structure‐activity relationships between the test compounds and the new stationary phase are discussed according to logP, logD and pKa values.