Separation parameters via virtual migration distances in high-performance liquid chromatography, capillary zone electrophoresis and electrokinetic chromatography

Among the various differential migration processes of separation, high-performance liquid chromatography (HPLC) and capillary zone electrophoresis (CZE) have emerged as the two major high-performance analytical techniques for separation of complex biological substances. In both HPLC and CZE with electroendoosmotic flow, the differential migration process can be divided into a separative component, which involves selective interactions with the stationary phase or differences in the electrophoretic migration velocities, and a non-separative component representing migration by convection that does not contribute directly to separation. The introduction of virtual migration distances leads to an additivity relationship for the two components that is applicable to both of the above techniques and facilitates the recognition of the underlying similarities as well as the expression and comparison of the various separation parameters. Examination of the key migration parameters led to the characterization and the classification of the various modes of CZE with electroendoosmotic flow. The treatment was extended to the analysis of capillary electrochromatography and micellar electrokinetic chromatography; two hybrid processes which exhibit features borrowed from HPLC and CZE. The use of virtual migration distances also led to a consistent and unified description of the characteristic parameters of these separation systems.