Hydrophilic Interaction Capillary Electrochromatography for the Separation of Polar Compounds

and Yan (5) reported that they successfully separated high polarity explosives using CEC with nonporous C18-coated material and a mobile phase with a low concentration of organic modifier and SDS added to the mobile phase to increase the wettability of the particle surface. Zhang and colleagues (9) also reported that very polar compounds could be separated by mixed-packing CEC with a stationary phase that was a physical mixture of strong cation-exchange and C18 materials. The hydrophilicity of the packing increased greatly because of the presence of the sulfonic acid group on the surface of the strong cation-exchange material, and a mobile phase with a low concentration of organic modifier could be used in this system to avoid bubble formation. Polar ionic compounds can be separated by ion-exchange CEC with high efficiency (10–12), and hydrophobic neutral solutes can be separated in ion-exchange CEC after adding surfactant to the mobile phase to dynamically modify the packing surface (13,14). A chromatographic technique called hydrophilic interaction chromatography has proven to be an efficient method for separatThe authors used hydrophilic interaction capillary electrochromatography (CEC) to separate polar compounds. Their system had a capillary column packed with a hydrophilic, strong cation-exchange material of poly(2-sulfoethyl aspartamide)-silica and a hydrophobic mobile phase, which typically contained 80% acetonitrile. The elution order of polar compounds in hydrophilic interaction CEC is similar to that obtained by normal-phase chromatography, and the retention of solutes increases with their hydrophilicity. The authors obtained column efficiencies of 79,000–111,000 plates/m with separation of some model polar compounds under optimal conditions. The repeatability of their system was good with relative standard deviations of approximately 0.4% and less than 0.7% for void time and solute retention factors, respectively, in 10 consecutive runs. Hydrophilic Interaction Capillary Electrochromatography for the Separation of Polar Compounds