Equilibria and microorganism studies with analytical separation techniques

The applications of analytical techniques to evaluate solute-ligand interactions and to analyze microbiological samples are discussed in this work. The dissertation is organized into two sections based on the natural division of studies done in the past several years. Part I includes studies involving the estimation of binding constants and partition coefficients and the modeling of pseudophase gas-liquid chromatography. The binding of solutes to pseudophases, such as micelles and cyclodextrins, is an important phenomenon in numerous areas of chemistry. Here, the ability of various native and derivatized cyclodextrins to sequester oral malodorous compounds and other volatile solutes was examined by measuring their association constants. Numerous techniques were utilized to determine the solute-cyclodextrin affinities. The results of this study indicate that cyclodextrins are capable of binding with a wide variety of oral malodorous compounds to varying degrees. The equations used in this study were then developed further and applied to the separation of several enantiomers using a methylated-cyclodextrin/polysiloxane stationary phase. These calculations allow the contributions from all three solute equilibria to retention and selectivity to be measured. This work was then extended to micellar/ionic liquid gas-liquid chromatography stationary phases, and the Abraham solvation parameter model was used in order to deconvolute the types of interactions responsible for analyte partitioning to these two phases. Part II of this dissertation focuses on the work done on the development of a rapid capillary electrophoretic sterility test. This technique coalesces all cells in a sample into a single peak and removes them from potential interferences in the sample matrix. Cationic surfactants were used in the run buffer to impart charge onto the microorganisms and sweep them out of the sample zone, while a plug of blocking agent induced cellular aggregation and negated the cells' electrophoretic mobility. A wide variety of bacteria are compatible with this method, and analysis times are typically less than 10 minutes. Single cell detection was accomplished via laser-induced fluorescence detection and fluorescent cell staining. By coupling this capillary electrophoresis method with fluorescence in situ hybridization, a method that utilizes fluorescently tagged nucleic acid probes to selectively stain specific microorganism species or classes, identification of microbial contaminants was achieved.