Use of a nematic liquid crystal for the gas chromatographic separation of aza-heterocyclic compounds

Gas-liquid chromatography of polychlorinated biphenyl congeners between a nematic liquid crystal phase and a nonpolar phase

“…One of these, Nfl'-bis[p-methoxybenzylidene]-, '-bi-p-toluidine (BMBT), was selected for the present study on PCB's, based on its solid-nematic transition temperature (181 °C) (3) and its ability to retain its nematic order in a supercooled state for a prolonged period of time at GLC column temperatures as low as 120 °C (7). In addition of PAH isomer separations, this liquid crystal also has been used for improved GLC separations of methyl naphthalenes (7), underivatized steroid epimers (8), experimental pharmaceuticals (9), azaheterocyclic compounds (10), and a restricted number of PCB isomers (11).…”

Synthesis and properties of high-temperature mesomorphic polysiloxane (MEPSIL) solvents: biphenyl- and terphenyl-based nematic systems

“…In contrast, it has been recognized for some time that liquid-crystalline (mesomorphic) stationary phases (the nematic state in particular) provide enhanced GLC separations of many isomeric species, including PAH, that are difficult or impossible to resolve by other traditional chromatographic techniques (1, [6][7][8][9][10][11][12][13]. Unlike most other common GLC solvents that provide separations based upon solute vapor pressure and/or differential solubility arising from specific energetic interactions, nematic stationary phases yield separations based upon differences in solute molecular shape or, in the instance of cholesteric phases, solute chirality.…”

High-temperature nematic liquid crystal for gas liquid chromatography

“…bi-p-toluidine (BMBT; reported by Kelker (1) to be the first synthesized by Janecke and Vorlander), for the separation of three-five ring polycyclic aromatic hydrocarbons has led to its application for the separation of environmental polycyclic aromatic pollutants (13)(14)(15) and metabolites (16,17). Steroids (18), bile acids (19), polychlorinated biphenyls (20), pharmaceuticals (21), and polynuclear azaheterocyclic air pollutants (22) were also separated by using liquid crystal phases. BMBT columns, however, have limited usefulness above 240 °C due to excessive column bleed.…”