Theory of electrophoretic focusing on an inverse electromigration dispersion profile

Electrophoretic focusing on an inverse electromigration dispersion (EMD) profile is based on a principle different from those of other electrophoretic separation methods. It has already proved its applicability in analytical practice by offering competitive separation performance and sensitivity and specific selectivity. It can be classified as an intermediate between field-driven and equilibrium gradient methods and is therefore interesting from the viewpoint of theory of separation methods. This work presents a comprehensive theoretical description of electrophoretic focusing on an inverse EMD profile comprising properties of the electrolyte system, formed gradients, and focused analyte zones. The separation properties are described in terms of resolution and peak capacity and their dependence on system and analyte properties is discussed from the viewpoint of how the counteracting phenomena of electromigration and dispersion are affected by electric current, voltage, and hydrodynamic and electroosmotic flow. The overall performance of the present method is shown to be comparable with other electrophoretic separation methods like zone electrophoresis or isoelectric focusing.