Evaluation of smectic biphenylcarboxylate ester liquid‐crystalline polysiloxane stationary phases for capillary column gas chromatography

Abstract

SummaryMesomorphic biphenylcarboxylate esters were coupled via flexible aliphatic hydrocarbon spacers to a polysiloxane backbone. The influence of spacer length, percent mesomorphic substitution, and crosslinking of the stationary phase on liquidcrystalline transition temperatures and on chromatographic performance was investigated. Unique selectivity and good efficiency over a wide temperature range for gum and crosslinked liquid-crystalline phases were demonstrated by the separation of various isomeric polycyclic aromatic compounds.

Analytical Methods for Determination of Polycyclic Aromatic Hydrocarbons (PAHs) — A Historical Perspective on the 16 U.S. EPA Priority Pollutant PAHs

“…Wise et al (50) demonstrated the similarity of LC behavior on C 18 phases with GC liquid crystalline phases for separations of PAHs. Liquid crystalline phases for PAHs separations were first introduced by Janini and coworkers (31,51) and later investigated in more detail by Lee and coworkers (52)(53)(54). The smectic liquid crystalline phase reported by Markides et al was capable of separating the critical pairs mentioned above.…”

Standard Reference Materials (SRMs) for the Determination of Polycyclic Aromatic Compounds--Twenty Years of Progress

“…Reversed-phase LC on a polymeric C 18 phase provides excellent separation of isomeric PAHs (9) (see discussion below), but a second independent technique was necessary to provide certified values for concentrations of several of these individual isomers. GC on a smectic liquid crystalline stationary phase exhibits high shape selectivity for PAH isomer separations (10,11), thereby providing a separation of PAH isomers similar to that achieved in LC with the polymeric C 18 phase (12).…”

“…FIGURE11. Shape selectivity (as indicated by α TBN/BaP ) of monomeric and polymeric C 18 phases plotted as a function of column temperature.…”

Sample Preparation for Chromatographic Analysis

“…Retention volumes may vary unpredictably with the amount of liquid phase and the type of support used [830,831]. New phases with a polysiloxane or hydrocarbon backbone containing liquid crystal functional groups provide higher efficiency and a wider working temperature range, as well as being compatible with modern technology for preparing immobilized phases on fused silica open tubular columns [834][835][836][837][838]. At low loadings most of the stationary phase is present as a surface film and solute retention occurs largely by interfacial adsorption.…”