This grant is in the general field of analytical and surface chemistry and in the subfield of separations science. Professor Sarah Rutan will study the structure of stationary phases used in liquid chromatography. By using a combination of optical spectroscopy of molecular probes in specific solvent environments she will determine the so-called solvatochromic parameters of the system. From this approach the fundamental structure and reactivity of the molecular species at the liquid solid interface can be determined. A better understanding of the mechanisms of molecular interactions which give rise to separations of molecular species in flow will result. Molecular interactions between probe molecules and liquid chromatographic stationary phases will be determined. Optical (uv-visible and infrared spectroscopic band shifts will be measured and analyzed to remove solution phase interferences. Dipolarity-polarizability, hydrogen bond acidity and basicity will allow an understanding of solvent based reactivity and adsorption effects underlying separations and other liquid solid interfacial systems. The particular solvent systems will include methanol, acetonitrile and tetrahydrofuran - water mixtures commonly used in high performance liquid chromatography. Hydrocarbon and phenyl modified silica as well as unmodified silica will be studied. The probe molecules include a series of nitroaniline dyes commonly used to probe solvent solute interactions. Unique capabilities to perform multicomponent analysis and eliminate the contributions of liquid phase effects will allow improvement over the current level of understanding of the dynamics of adsorption at the molecular level in solution.
