Supercritical fluid chromatography for analysis of liquid crystalline materials of technological interest

Fifteen novel liquid crystalline materials were used to survey the potential of supercritical fluid chromatography (SFC) with UV detection for separation of liquid crystal mixtures. A variety of separation conditions were used to outline the behaviour of this type of analytes in the SFC environment. Eight stationary phases were employed to evaluate their aptness for application in liquid crystal characterization including diol, 2-picolylamine, 1-aminoanthracene, pentafluorophenyl, octyl and octadecyl chemistries. Three types of octadecyl stationary phases were used to elucidate how the different particle type and the presence/absence of shielding polar groups affect the separation. Methanol, ethanol and 2- propanol and their mixtures with acetonitrile were tested as cosolvents and the effects of the mobile phase on retention/separation are also evaluated. The combined results provide a wide comparison of stationary phases based on their ability to distinguish structurally related compounds. The differences in chromatographic behaviour and its trends depending on both mobile and stationary phases selection highlight the versatility of the SFC. The solutes belong to two groups (ferroelectric nematic and photosensitive mesogens) and two corresponding mixtures were prepared as model samples, comprising eight and seven compounds, respectively. The pentafluorophenyl stationary phase (PFP) proved to be the most suitable from all tested columns - both prepared blends were separated to baseline on the XSelect HSS PFP column in under seven minutes.