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Solid support surface effects on the chromatographic behavior of a liquid crystal stationary phase

Journal of Chromatography A
Publication Date
DOI: 10.1016/s0021-9673(00)99949-7


Abstract The present paper investigates the behavior of p-( p-ethoxyphenylazo)phenyl undecylenate (EPAPU) liquid crystal as a stationary phase coated on glass beads in gas chromatography under a variety of conditions. The columns studied were 0.69% and 0.10% (w/w) mesophase coated on neutral glass beads and 0.11% (w/w) on acid-treated beads. Unlike previous studies no hysteresis was found in the capacity ratio, k′, and the plate height, H, as a function of the temperature. However, around the chromatographically observed melting point, k′ and H varied with time at a given temperature. The same behavior was found around the solidification point. Surface orientation effects and the “swarm” model were used in trying to explain the above phenomena. When comparing EPARU coated on acid-treated glass beads and on neutral beads different kinetics behavior (in terms of H) around the melting point was observed. The diffusion coefficients of p-xylene in EPARU and activation energies in the nematic range were obtained. The lightly loaded columns gave very similar results which differed from the heavily loaded columns.

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