Isocratic Elution Chromatography (Molecular Biology)

Continuous elution of analytes in a chromatographic separation with only one mobile phase (a single solvent or a constant-composition solvent mixture) throughout the separation is known as isocratic-elution chromatography. This method is frequently very time-consuming, and the analytes are eluted as broad bands if they are strongly adsorbed on the column. Therefore, it is common to follow an initial period of isocratic separation with an elution gradient, in which the polarity of the initial mobile phase is progressively changed by the continuous programmed addition of increasing quantities of a second mobile phase to speed up the rate of elution and to sharpen eluent zones that are trailing or fronting. A description of the theory of isocratic-elution chromatography is beyond the scope of this article, and interested readers are directed to the excellent chapter written by Jandera and Churacek (1).