Theoretical study of the separation mechanism of ionizable compounds in capillary electrochromatography

The migration mechanism of ionizable compounds in capillary electrochromato graphy (CEC) is more complicated than in high performance liquid chromatogr aphy (HPLC) due to the involvement of electrophoresis and the second chemic al equilibrium. The separation mechanism of ionizable compounds in CEC has been studied theoretically. The electrochromatographic capacity factors of ions (k *) in CEC and in the pressurized CEC are derived by phenomenologica l approach. The influence of pH, voltage, pressure on k* is discussed. in a ddition, the k * of weak acid and weak base are derived based on acid-base equilibrium and the influence of pH on k * is studied theoretically.