Preferential Solvation of Solute as a Source of Ghost Peaks in Liquid Chromatography

Abstract

Ghost peaks in liquid chromatography (LC) with mixed eluents can be brought about by preferential solvation of solute by one of the components of eluent. The preferential solvation causes the change of composition of “dialyzed solvent,” i.e., of the bulk solvent outside solvate shells of solute molecules. In the chromatographic column, the zone of dialyzed solvent is separated from the solute molecules and corresponding ghost (vacant) peak occurs. The vacant peaks of preferential solvation: (a) complicate the interpretation of chromatograms; and (b) may be used in the quantitative evaluation of the phenomenon of preferential solvation. The occurence of vacant peaks of preferential solvation is demonstrated in the system Sephadex LH-20 — benzene/methanol 77.8/22.2 v/v — by injecting a series of polymers, oligomers, and low molecular substances.