Preparation of a dibenzylated 1,4-diazacyclohexane-derived strong anion-exchange stationary phase

• A novel anion exchange stationary phase of 1,4-difunctional was developed.
• Separation of carboxylic acids was benefited from the complicated mechanisms.
• Carboxylic acids were separated in the order of decreasing in their pKa values.
• No apparent discrimination of peak shapes was observed for different samples.

This paper reports the preparation of a novel, silica-based, strong anion-exchange stationary phase from a 1,4-diazacyclohexane derivative. To prepare the difunctional strong anion-exchange stationary phase, activated silica beads were first bonded with 3-chloropropyltriethoxysilane and then reacted with 1-methylpiperazine followed by benzyl chloride. The silica beads, the strong anion-exchange stationary phase and its precusors were instrumentally characterized. Aromatic acids were separated with non-aqueous anion-exchange chromatography. After elution with eluant prepared in mixed solvents of water and methanol, the resulting 1,4-diazacyclohexane-derived, difunctional, strong anion-exchange stationary phase exhibited good separation and selectivity for the aromatic acids investigated. The effects of eluant pH, eluant ion concentration and solvent composites on the separations were investigated. Organic acids with different substituents were eluted in order of decreasing dissociation coefficients, with no observable peak shape differences.