ISOELECTRIC-FOCUSING FIELD-FLOW FRACTIONATION AND CAPILLARY ISOELECTRIC-FOCUSING WITH ELECTROOSMOTIC ZONE DISPLACEMENT - 2 APPROACHES TO PROTEIN-ANALYSIS IN FLOWING STREAMS

A comparison of the separation of three proteins by two focusing methods in flowing streams, isoelectric focusing field-flow fractionation (IEF4) in a trapezoidal cross-section channel and capillary isoelectric focusing with electroosmotic zone displacement (cIEF) in an uncoated, open-tubular fused-silica capillary, is presented. In IEF, a hydrodynamic flow with a characteristic flow velocity profile as well as an electric force field and a chemical equilibrium (pH) gradient arranged perpendicular to the direction of flow are employed for separation. cIEF uses an electrokinetic plug flow with the separating electrical and chemical fields parallel to its direction. Protein zones are monitored by conventional detectors developed for liquid chromatography and capillary electrophoresis respectively. With current instruments, separation by cIEF is shown to be characterized by higher efficiency and resolution than separation in IEF4. However, the latter method operates at much lower voltages and is simpler to apply for micropreparative purposes. The time intervals required for separation and analysis in the two methods are comparable.