ISOELECTRIC-FOCUSING FIELD-FLOW FRACTIONATION - EXPERIMENTAL-STUDY OF THE GENERATION OF PH GRADIENT

Isoelectric focusing field-flow fractionation is a method for the separation of ampholytes using, in addition to the electric field and pH gradient, the flow of the carrier liquid 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. It makes it possible to decrease the absolute value of the voltage while maintaining a high field strength and results in a lower Joule heat production. Moreover, the laminar flow of the carrier liquid stabilizes the pH gradient against convection. A channel was designed from which ampholyte sampes can be taken at twelve different positions. pH value of the samples taken were measured with the aid of a capillary pH electrode. The pH dependence of the applied voltage, flow-rate of ampholyte solutions and concentrations of the solutions of ampholyte and electrode electrolytes were measured at different channel positions. It follows from the measurements performed so far that the pH gradient generation is sufficiently fast and reproducible for use in isoelectric focusing field-flow fractionation.