Triptycene-based dicationic guanidinium ionic liquid: A novel stationary phase of high selectivity towards a wide range of positional and structural isomers.

This work presents a new triptycene-based dicationic guanidinium ionic liquid (TPG) as the stationary phase for gas chromatography (GC). To our knowledge, this is the first example of employing a dicationic guanidinium ionic liquid (GIL) for chromatographic analyses. As a result, the TPG column exhibited moderate polarity and column efficiency of 3840 plates/m and 3120 plates/m measured by naphthalene and 1-octanol at 120 °C, respectively. Particularly, the TPG column exhibited distinctly advantageous performance for the challenging Grob test mixture and the isomer mixture of phenols and anilines over the monocationic GIL and its counterpart with dicationic immidazolium units (TP-2IL). Also, it showed higher selectivity towards the isomers of alkanes, alcohols, diethylbenzenes, bromotoluenes, bromonitrobenzenes than the commercial DB-35MS column. Moreover, the TPG column achieved improved thermal stability over the GIL column and excellent repeatability with the RSD values of 0.01-0.05% for run-to-run, 0.11-0.24% for day-to-day and 2.4-4.1% for column-to-column. Its application to GC-MS analysis of the essential oil of Mentha haplocalyx proved its good potential for analysis of complex samples.