Gas chromatography at finite concentrations. Part 3.—Theory of frontal and elution techniques of thermodynamic measurement

Abstract

Gas chromatography theory is extended to the measurement of thermodynamic properties in binary gas + liquid and gas + solid systems at finite concentrations of the volatile component. The four gas chromatographic methods: frontal analysis (FA); frontal analysis by characteristic point (FACP); elution by characteristic point (ECP); and elution on a plateau (EP) are treated. All four methods are related through consideration of the movement of a zone of given constant concentration, for which a generalised retention equation has previously been derived.¹ Earlier treatments of each technique by other authors lead to accurate results only at low gas-phase concentrations of solute. To remove this limitation, the effects of gas imperfection, non-sharp boundary input profiles, and velocity variation due to sorption and desorption of solute, are here taken into account. Expressions are derived, and methods of calculation proposed, which give the amount of sorbed material explicitly and without use of cumbersome iterative procedures.