HIGH-PERFORMANCE DISPLACEMENT ELECTROPHORESIS IN 0.025-MM TO 0.050-MM CAPILLARIES COATED WITH A POLYMER TO SUPPRESS ADSORPTION AND ELECTROENDOSMOSIS

The risk of adsorption onto the walls of an electrophoresis tube increases with decreases in the bore of the tube and in the ionic strength (conductivity) of the buffers. It is therefore important to suppress adsorption in high-performance displacement electrophoresis where the diameter of the tube is often as narrow as 0.025 mm and the electrical conductivities are low (as they are in most displacement electrophoresis experiments at the steady state), for instance 10(-4)-OMEGA-1 cm-1. This can be accomplished by coating the electrophoresis tube with a thin (preferably monomolecular) layer of a hydrophilic non-ionic polymer, which also eliminates electroendosmosis. The narrow-bore tubes permit high field strengths without serious thermal zone broadening and therefore have the advantage of affording fast runs with high resolution (displacement electrophoresis often gives lower thermal zone broadening at a given field strength than does zone electrophoresis, because the average conductivity in the former method is usually lower than the conductivity in the latter). An analysis of serum proteins at a field strength of 860 V/cm took about 10 min. In the presence of continuous spacers the resolution increased dramatically: human serum could be resolved into about 30 components. Twelve nucleotides were separated within 10 min. Displacement electrophoresis in coated tubes gives reproducible electropherograms, which makes the method suitable for clinical analyses, exemplified by a study of serum from a patient with multiple myeloma. The zone broadening is considered with regard to diffusion, Joule heat and adsorption. The terms displacement electrophoresis and isotachophoresis are discussed.