Partition Isotherms and Gas-Liquid Chromatography

Abstract

THE various well-known theories of gas-liquid chromatography all assume a linear ‘partition’ isotherm, that is, the concentration of a solute in the stationary liquid phase is a linear function of the concentration in the gas phase; also the theories are unanimous in predicting symmetrical elution peaks. Asymmetrical peaks, when they occur, are variously ascribed to ‘overloading’ of the column, lack of attainment of equilibrium, adsorption on the solid support and at the gas-liquid interface, and finally, non-ideal solution behaviour¹. Non-ideality is taken to mean that the solutions show deviations from Raoult's law. We wish to make two points; first, that partition isotherms are frequently markedly non-linear and, second, that non-ideal solution behaviour is not important in determining elution peak symmetry, but that isotherm shape is. We base our arguments on the results of experiments which were aimed at the determination of partition isotherms by a static method.