Fundamental solvatochromic and thermodynamic studies of complex chromatographic media.

摘要

To appreciate the retention mechanism in reversed-phase liquid chromatography (RPLC) it is necessary to understand the physical processes in aqueous solutions and how they vary with composition and cosolvent. In this work, head-space gas chromatography (HSGC) is used to measure the infinite dilution activity coefficients ({dollar}ysp{lcub}infty{rcub}{dollar}) of polar solutes in water and a diverse set of aqueous solutions. This will allow us to investigate the retention mechanism of polar solutes in RPLC. The ability of polar solutes to self associate will be studied using the composition dependence of {dollar}ysp{lcub}infty{rcub}{dollar}, a direct measure of the second virial coefficient. {dollar}ysp{lcub}infty{rcub}{dollar} will also be measured in deuterium oxide (D2O), allowing us to calculate the free energy of transfer from H2O to D2O, {dollar}rmDelta Gsb{lcub}H2O/D2O{rcub}.{dollar} These data will make a significant contribution to the theory of enthalpy-entropy compensation and the hydrophobic effect. Measurements of free energies of transfer using HSGC will first be verified by measuring free energies of transfer from neat to water saturated n-octanol, {dollar}rmDelta Gsb{lcub}O/OW{rcub}.{dollar} The effect of water on the chemical properties of n-octanol will be confirmed using solvatochromism.; Solvatochromism will also be used to study the chemical properties of aqueous mixtures and how they affect a model bulk stationary phase; a direct test Partition Model of retention in RPLC. Micelles have been used as models of the bonded-phase in RPLC and as mobile phase additives. Therefore, solvatochromism will be used to probe the physical and chemical properties of micelles in aqueous and nonaqueous solutions. From these data, a better understanding of the bonded-phase in RPLC and micellar chromatography should develop.