Preparation of a 1,4-Diazabicyclo[2.2.2]octane sulfonate betaine zwitterionic stationary phase and comparative evaluation of its separation performance in hydrophilic interaction chromatography

Background

Hydrophilic interaction liquid chromatography (HILIC) offers an alternative approach for efficient separation of polar molecules on polar stationary phases. The development of hydrophilic stationary phases with novel zwitterionic structures represents a promising approach to improving the efficiency of separations and accommodating the analysis of polar compounds in complex samples.

Results

This work details the preparation and thorough evaluation of the novel zwitterionic stationary phase, Sil-DBO-PS, composed of a 1,4-diazabicyclo[2.2.2]octane cation and a sulfonate anion. The chromatographic behavior of Sil-DBO-PS was investigated under varying eluent conditions, including water phase ratio, salt concentration, and pH, while interaction mechanisms of Sil-DBO-PS were explored through Van't Hoff plots, Tanaka HILIC tests, and modified linear solvation energy relationships. These studies revealed that the zwitterionic group introduced a range of interactions, including hydrophilic partitioning, hydrogen bonding, and electrostatic interactions. The Sil-DBO-PS column outperformed two commercial columns in terms of separation efficiency for polar analytes, such as nucleosides, vitamins, and benzoic acids, highlighting its enhanced capability for polar compound separation. Furthermore, Sil-DBO-PS stationary phase demonstrated satisfactory reproducibility in the separation of hydrophilic compounds.

Significance and novelty

The development of the Sil-DBO-PS zwitterionic stationary phase significantly enhances the separation efficiency and selectivity for polar compounds in HILIC, offering superior performance over commercial columns for challenging analytes. This novel stationary phase, with its diverse interactions, provides a promising tool for the analysis of hydrophilic and complex samples.