Steady-state models in electrophoresis: from isotachoporesis to capillary zone electrophoresis

Although all electrophoretic techniques are closely allied and controlled by the same rules, we often distinguish between steady-state and dynamic models in the modeling of electrophoretic processes, whereby steady-state models are applied for isotachophoresis (ITP) and dynamic models are applied for other electrophoretic processes, wherein a steady-state is not reached. This paper shows how, starting from a mathematical model for the steady-state in ITP, mathematical models can be derived for several modifications of ITP and that even nonsteady-state processes can be estimated by a repeated application of a steady-state model. In this way all parameters in sample zones in capillary zone electrophoresis (CZE), through which temporal electropherograms can be simulated, can be calculated. Realistic simulations can be obtained for zone electrophoretic processes, for which the electrodispersive character is the dominating peak broadening mechanism, and simulated electropherograms resemble measured electropherograms concerning migration times, peak shapes, fronting or tailing character and the question of peaks and dips.