Adjustment of stationary phase selectivity in gas—liquid chromatography by using mixed liquid phases

Abstract

Contrary to liquid—liquid chromatography, where binary, ternary and quarternary mixed solvents have been systematically investigated and extensively applied, very few systematic studies on mixed stationary liquid phases have been undertaken in gas—liquid chromatography (GLC). Except for mixtures of chemically analogous polymric constituents resulting from production processes, little use is made of mixed solvents in GLC. In this work, “binary” mixed solvents were studied as stationary liquids in GLC. Linear and non-linear relationships between the capacity factor and phase composition were found experimentally. In the non-linear case curves with minima were observed. It was confirmed experimentally that adsorption on the solid support is negligible. The shape of the relationship is discussed in terms of thermodynamic theory. The exploitation of the selectivity of mixed solvents in GLC separations is demonstrated. It is shown that columns with composite solvents as stationary phases and coupled columns with single phases aer equivalent if there is a linear relationship between the capacity factor and the statinary liquid phase composition. It is demonstrated that switching of columns can be successfully empployed in achieving or optimizing a separation of GLC.