Metallomesogens as stationary phases for ligand exchange gas chromatography .1. The use of nickel and zinc complexes of 4-decanoxydithiobenzoic acid for the separation of polycyclic aromatic hydrocarbons and dialkyl sulfides

Metallomesogens based on 4-decanoxydithiobenzoic acid (DDTBA) metal complexes were prepared and applied to the separation of polycyclic aromatic hydrocarbons (PAHs) and dialkyl sulfides. The mesophase of DDTBA-Ni was stable at temperatures ranging from 140 degrees to 230 degrees C and that of DDTBA-Zn was stable at temperatures ranging from 137 degrees to 173 degrees C. 5% of each material was coated on Chromosorb and then packed in a 2.1 mx3.2 mm i.d. spiral glass column. Factors affecting the retention time and the selectivity were studied. The results indicate that the retention time is greatly affected by the molecular geometry in addition to the vapor pressure and polarity of the solutes, and that a DDTBA-Ni column is adequate for the separation of PAHs, whereas a DDTBA-Zn column is suitable for the separation of dialkyl sulfides. Van't Hoff plots as a function of temperature indicate that phase transitions were occurring. Thermodynamic properties of the analytes in this system were also studied.