Solution and adsorption thermodynamics in propylene glycol by gas chromatography : A comparative study with other polyhydroxylated solvents

The retention volumes of eighteen hydrocarbons representative of different families and of acetone, diisopropyl ether and three chloromethanes were measured at four temperatures within the range 12–22°C on columns containing five different percentages of propylene glycol (PG) as the stationary phase. The relative magnitudes of the adsorption on PG, on formamide and on four glycols are compared and discussed in terms of the thermodynamic properties of the bulk mixtures with hydrocarbons, From this comparison, PG is found to possess the weakest adsorption effects, and some of the solutes studied exhibit no adsorption within experimental error. The thermodynamic properties of solution in PG are calculated and compared to those in formamide and in the glycols. Recent extensions of the regular solutions model are inefficient for calculating infinite dilution activity coefficients, but yield a very acceptable correlation between heats of solution and solute solubility parameters.