ISOELECTRIC-FOCUSING FIELD-FLOW FRACTIONATION .2. EXPERIMENTAL-STUDY OF FOCUSING OF METHYL RED IN THE TRAPEZOIDAL CROSS-SECTION CHANNEL

Isoelectric focusing field-flow fractionation is a technique for the separation of ampholytes using in addition to the electric field and pH gradient the flow of the carrier ampholyte solution through the fractionation channel as the third active separating factor. Flow action permits a decrease in the channel dimension in the direction of the electric field and thereby also a decrease in the absolute values of the voltage while keeping a high field strength, which results in lower Joule heat production and a shorter time required for focusing. Focusing of methyl red in the trapezoidal cross-section channel was investigated as a function of the applied voltage and flow-rate of the carrier ampholyte solution. On the basis of the results obtained, it is obvious that methyl red is readily focused under suitable conditions inside the channel. Focusing is more efficient at higher electric field strengths and lower flow-rates of carrier ampholyte solution.