In this study, the thermodynamic properties of agar were examined by the inverse gas chromatography method. The dispersive surface energy, \(\:{\gamma\:}_{S}^{D}\) of the adsorbent was determined using the Schultz, Dorris–Gray, Donnet–Park, and Hamieh methods in the temperature range of 303.2–328.2 K. To evaluate the polymer-solvent interaction parameters, the specific retention volume of the solvents, \(\:{V}_{g}^{0}\) values were determined using various nonpolar and polar solvents in the temperature range of 373.2–398.2 K. Then, from these data, the values of the Flory-Huggins theory polymer-solvent interaction parameters, \(\:{\chi\:}_{12}^{\infty\:}\) , equation of state theory, polymer-solvent interaction parameters, \(\:{\chi\:}_{12}^{*}\) , effective exchange energy parameters, \(\:{X}_{eff}\) and solubility parameter of agar, \(\:{\delta\:}_{2}\) were calculated. Additionally, the isomer separation power of agar, \(\:{\alpha\:}_{A}\) was assessed with selected isomer pairs in the temperature range of 303.2–333.2 K.
