Properties of the Solute-Stationary Liquid Interactions in Gas Liquid Chromatography

Abstract

The solute-stationary liquid interaction in gas liquid chromatography (GLC) was determined using Eyring's model. The interaction was determined to be the physical adsorption. The descriptor sigma(M) was derived and estimated by van der Waals interactions. The CH/pi interaction energies were calculated by Tsuzuki et al. using the high-level ab initio calculations. The CH/pi interaction energy was concluded to consist of the dispersion energy (Edis) rather than the electrostatic (Ees) and charge-transfer (Ect) energies. These energies were in good agreement with our descriptor sigma M. Furthermore, the macroscopic sigma M also had microscopic support through the weak CH/pi interactions. In substituted benzenes, regression analyses were carried out using sigma M for the relative retention values, log gamma, as a measure of the solute-stationary liquid interaction. The analyses revealed good results under non-polar conditions. The log gamma values therefore consisted primarily of contributions from the dispersion interaction and the CH/pi complex. Moreover, these values were useful when added to the electrostatic term (our descriptor sigma es) for polar solutes. That is, the log gamma values were estimated by the regression analyses using both sigma M and sigma es, and were in good agreement with the predicted values.