Metallomesogens as stationary phases for the separation of phenols by gas chromatography Original Research Article

Metal complexes of 4-decanoxydithiobenzoate (DDTBA) and 4-(dec-9′-en-1′-oxy)dithiobenzoate siloxane polymer (P-DODTBA) were prepared and used as stationary phases in ligand-exchange gas chromatography for the separation of phenols. A better separation of phenols was achieved in the liquid crystalline state than in the solid state. Vanʹt Hoff plots as a function of temperature indicated that phase transitions were occurring. From specific retention volumes measured at various temperatures in each of the DDTBA-Zn and DDTBA-Ni fluid phases, the thermodynamic behavior of phenols is discussed. The DDTBA-Zn phase showed a higher solute–solvent interaction than DDTBA-Ni. Moreover, DDTBA-Ni phase was more appropriate for the separation of lower volatile phenols. A similar property was exhibited by the metal complexes of P-DODTBA. A spiral glass column (2.1 m×3.2 mm i.d.) was prepared from 5% DDTBA-metal complex deposited on Chromosorb. By dynamic coating, wall-coated P-DODTBA-metal complex capillary columns (12 m×0.25 mm i.d.) were also prepared as stationary phases for the separation of phenols. Factors affecting the retention and the sample selectivity on both the packed column and the capillary column were examined. The calibration graphs for phenol determination were linear over the range of 64–1600 μg ml−1 (packed column) and 16–400 μg ml−1 (capillary column). The 2σ mass detection limits of most phenols are less than 30 ng for packed column and 4 ng for capillary column.