Liquid Chromatographic Separation of Polar Organic Compounds Using Strong Anion-Exchanger as the Stationary Phase and Pure Water as the Mobile Phase

Abstract

A unique high performance liquid chromatographic system for the separation of polar organic compounds is described. Strong anion-exchanger was used as the stationary phase and pure water was used as the mobile phase. When the strong anion-exchanger was conditioned with pure water as the mobile phase, the fixed ionic site with its counterion functioned as a zwitterionic stationary phase.

This facilitated the separation of the polar organic compounds without need for ionization of the analytes. A strong commercial anion-exchanger (polyacrylate-based type) and a laboratory-made one (ODS-based type; obtained by dynamically coating hexadecyltrimethylammonium salts on the reversed-phase ODS surfaces) were chosen to represent the stationary phases. Five purine and pyrimidine bases and eight nucleosides were chosen to represent the polar organic analytes. All of these polar organic analytes were successfully separated and rapidly eluted with pure water as the mobile phase. Separation mechanisms involved were investigated and the experimental results suggested that electrostatic interaction was the main mechanism for separation in polyacrylate-based stationary phase; while, electrostatic and hydrophobic interactions were dual mechanisms for separation in ODS-based stationary phase.