Characterization of solvent properties of methyl soyate by inverse gas chromatography and solubility parameters

A study on the physicochemical properties of methyl soyate (or soybean oil fatty acid methyl esters) is very important for its use as a substitute solvent in liquid–liquid separations. Towards this end, the Hildebrand solubility parameter of methyl soyate was determined using an inverse gas chromatographic technique (IGC). Solute specific retention volumes of 19 solutes (varying in solubility parameter) were determined using methyl soyate as the stationary phase. Flory–Huggins interaction parameters between the solvent (methyl soyate) and the solutes, calculated using the solute retention data, were then used in studying the miscibility of the solute in the solvent at infinite dilution. The Hildebrand solubility parameters of methyl soyate varied from 8.03 to 7.49 cal^1/2cm^−3/2 at temperatures from 50–85 °C. The solubility parameter of methyl soyate at room temperature conditions extrapolated from the experimental data was found to be 8.49 cal^1/2cm^−3/2. This value is consistent with those obtained using group contribution methods for model methyl esters of C18 fatty acids found predominantly in methyl soyate. Hansen solubility spheres were plotted using the literature data (including this study) for the interactions of methyl soyate with 41 solutes to determine the three dimensional solubility parameter of methyl soyate at room temperature. These calculated solubility parameter values were consistent with those determined experimentally via IGC.