Focusing counterparts of electrical field flow fractionation and capillary zone electrophoresis. Electrical hyperlayer field flow fractionation and capillary isoelectric focusing

Efforts are currently being undertaken to develop electrical hyperlayer field flow fractionation (EHFFF) and capillary isoelectric focusing (CIEF) as fully instrumental approaches for the analysis of amphoteric samples, such as peptides and proteins. In these techniques a pH gradient parallel to an applied electric force field is employed for sample discrimination according to differences in isoelectric points. EHFFF is performed in a thin ribbon-like channel containing a mobile phase with the electric field perpendicular to the flow direction, whereas CIEF utilizes a quiescent solution with the electric field parallel to the column axis. The principle of EHFFF, the design of EHFFF instrumentation and first results are discussed together with the differences and similarities between EHFFF and CIEF.