Forecasting Enthalpies of Solution (-ΔHsol) and Enthalpies of Vaporization (ΔHvap) of Solute in Gas Chromatography

Abstract

The enthalpy of solution of (-ΔH_sol) n-alkanes and fatty acid methyl esters (FAMEs) on BP1(non-polar) column can easily be estimated from their carbon numbers (z) by the equation (1) whichwas proposed by Krisnangkura et al. [1]

Ink = a + bZ + c/T + dZ/T

where k is retention factor, T is the absolute temperature, and a, b, c and d are thermodynamicconstants of the column.

The advantage of the present method compared to the van't Hoff plot method is that the -ΔH_sol of solute in the homologous series can be directly estimated and by passing the GCanalyses.

In addition, combining the proposed method to that of Chickos et al. [2] could be used forcalculating the molar enthalpy of vaporization (ΔH_vap at 298.15 K). The highest difference betweenthe calculated ΔH_vap and reference data are 1.74% and 2.56% for the standard n-alkanes and FAMEs,respectively.

It is speculated that the -ΔHsol and ΔHvap of other compounds such as ketones, aldehydesand fatty alcohols could also be estimated by using the methods as proposed in this study.

Keywords : Fatty Acid Methyl Ester / Gas Chromatography / n-Alkane / Enthalpy ofSolution / Enthalpy of Vaporization