Recycling electrophoretic separations: Modeling of isotachophoresis and isoelectric focusing

The conventional, one-dimensional model that is the foundation for the dynamic simulation of electrophoretic separations is modified to describe the essential features of recycling electrophoresis instruments. Simulations are performed for the isoelectric focusing (IEF) and the isotachophoresis (ITP) modes. Results are compared with experimental data from prototype recycling free-flow IEF and ITP devices. Agreement between the experiments and the simulations is favorable, though electrode and electroosmotic effects, which are omitted from the model, are noticeable in the IEF instrument. Three parameters relevant to the design of recycling electrophoresis devices, viz. the number of ports for the recycle manifold, the residence time in the separation chamber per cycle, and the current density, are investigated with the model.