COMPARISON OF 4 LIQUID-CRYSTAL STATIONARY PHASES USED ABOVE AND BELOW THEIR MELTING-POINT TEMPERATURES FOR THE GAS-CHROMATOGRAPHY OF SOME VOLATILE OIL CONSTITUENTS

All four liquid crystal stationary phases used for the gas chromatography of volatile oil constituents function below their melting points, but the azoxydiphenetole (ADP)-packed column does not exhibit reliable supercooling. Safrole always preceding anethole provides an identifying test for these liquid crystal phases. Various distinctive shifts in solute sequence were noted for each phase. An "MPMS" polysiloxane capillary gave the highest relative retention times of the four phases and is required for satisfactory peaks of monoterpenes with a terminal polar group, like geraniol. It is also good for polar aromatics like thymol, although bis(methoxybenzylidineanil-chloroaniline) in a packed column is an alternative. Linear ether aromatics like estragole can be studied on all four phases, which have this structure themselves. Whilst ADP may be best for terpene hydrocarbons, especially caryophyllene, bis(methoxybenzylidineanil-bi-toluidine) is the best general purpose liquid crystal for packed columns.