Amphiphilic selectivity of guanidinium-based ionic liquid stationary phase for structural and positional isomers

Abstract

This work investigated the selectivity of guanidinium-based ionic liquid (GBIL), namely N,N,N′,N′-tetramethyl-N′′,N′′-dioctylguanidinium bis(trifluoromethylsulfonyl)imide (DOTMG-NTf₂), in gas chromatographic (GC) separations on the basis of our previous work. The fabricated GBIL capillary column exhibited column efficiency of 4320 plates per m and its selectivity and retention behaviours were explored with various samples including the mixtures of 15 analytes of diverse types, and structural and positional isomers. In this work, we found the intrinsic amphiphilic selectivity of the GBIL phase for nonpolar and polar analytes, showing advantages over the conventional polar phase for GC separation of analytes of a wide range of polarity. Most interestingly, it exhibits unique prolonged retention for linear alkanes, which has not been reported for polar stationary phases. Also, this work presents a new perspective regarding the retention behaviours of GC stationary phases.