Determination of gas-liquid partition coefficients of several organic solutes in trihexyl (tetradecyl) phosphonium dicyanamide using capillary gas chromatography columns.

We report here gas-liquid partition constants and activity coefficients for thirty-seven volatile organic solutes in ionic liquid trihexyl(tetradecyl)phosphonium dicyanamide measured by gas-liquid chromatography using capillary columns. Four capillary columns with exactly known phase ratios were constructed and employed to measure the solute retention factors at four temperatures between 313.15 and 343.15 K. The partition coefficients were calculated from the slopes of the linear regression between solute retention factors and the reciprocal of phase ratio at a given temperature. The partition coefficients thus calculated are free from errors due to the contribution to retention from gas-liquid interphase adsorption. For these reason, reliable solute's infinite dilution activity coefficients can be obtained, as well as partition enthalpies and entropies. A thorough discussion of the uncertainties of the experimental measurements and the main advantages of the use of capillary columns to acquire the aforementioned relevant thermodynamic information was performed.