(218g) Dilute Solution Thermodynamic Study of Phosphatidylcholine - Organic Solute Systems Using Inverse Gas Chromatography (IGC)

A fundamental understanding of solute-solvent interactions is critical in the design of separation processes such as liquid solvent or supercritical fluid extraction.  Toward this end, dilute solute-solvent interactions have been determined using inverse gas chromatography (IGC) for twenty-three solute – phosphatidylcholine (PC) systems over the temperature range of 55 – 105^oC.  Utilizing a purified soya-derived PC (Biolipon 95), several IGC columns were prepared using 45/60 Mesh, DMCS-treated Chromasorb G column packing, allowing a matrix of IGC-derivable data to be accumulated at infinite dilution, such as mole and weight fraction activity coefficients, Henry’s Law and partition coefficients, interaction and solubility parameters, as well as heats of solution and mixing.  Mole fraction activity coefficients of the organic solute probes in PC show both positive and negative deviations from Raoult’s Law and can be used to understand and optimize the choice of extraction-separation conditions.  Activity coefficients less than unity are exhibited by both aromatic and chlorinated classes of solutes and particularly ethanol – all solute activity coefficients showing the excepted trend with increasing temperature.  The experimental determined solubility parameters (δ) for PC over the above-stated temperature range vary from 20.5 – 18.3 MPa^1/2, δ data which has not been available previously.  Enthalpy data, i.e., heats of solution and mixing indicate that at this concentration, that the recorded heats of solution are dominated by the heats of solute vaporization.  The utilization of this IGC-derived data base will be discussed with respect to using it in the supercritical fluid extraction, dissolution, and purification of phospholipids.