Molecular-statistical calculation of retention volumes in gas adsorption chromatography

Abstract

The retention volumes, V R , for a series of hydrocarbons in gas adsorption chromatography on the basal face of graphite at zero surface coverage were calculated by a semi-emperical molecular-statistical method. The potential function of the interaction between a molecule and a surface is assumed to be equal to the sum of the potential functions of the interaction between atoms of the molecule and atoms of the adsorbent. The potential functions of the interaction between the C and H atoms of saturated hydrocarbon molecules and the C atoms of the graphite lattice (the atom-atom potential functions) were estimated by methods according to the theory of the intermolecular interactions and were corrected using experimental adsorption data for methane, ethane and propane on graphitized thermal carbon blacks. The calculated values of V R for all the saturated hydrocarbon molecules considered ( n-butane, isobutane, n-pentane, neopentane, cyclopentane, n-hexane, and cyclohexane) are in good agreement with the experimental values of V R on graphitized thermal carbon blacks. The calculations of V R for unsaturated and aromatic hydrocarbon molecules made it possible to estimate the difference between the potential functions of interaction of the C atoms of saturated, unsaturated, and aromatic molecules with graphite.