Use of Mixed Phases for Enhanced Gas-Chromatographic Separation of Polycyclic Aromatic Hydrocarbons. III. Phase-Transition Behavior, Mass-Transfer Non-Equilibrium, and Analytical Utility of Mesogen Solvents

摘要

Previous studies of the gas-chromatographic separation of polycyclic aromatic hydrocarbons have shown that open-tubular (capillary) columns containing liquid crystal solvents in admixture with silicone gums exhibit both high efficiency and high selectivity. Detailed here, for the first time, are selected analytical and physicochemical properties of a representative example of a unique class of phases which comprise silicone polymers with mesogenic side-chains. The retentions and relative separations achieved with the polymer resemble those found with a blend of 20% (w/w) BBBT with SE-52. However, the polymer exhibits a higher useful temperature range, lower volatility, and higher column efficiency. Relative retentions (alpha values) can differ by as much as a factor of three over a five-degree temperature range, and blending the mesogenic polymer with silicone diluents lowers the nematic transition temperature by as much as eighty degrees. The properties of mesogenic silicones thus provide an unprecedented spectrum of adjustable parameters for the quantitative control of solute retention and retention order, that is, means of optimization of separations. (ERA citation 07:059795)