A new trend in GC Selectivity: ion liquid Stationary phases

The choice of the proper stationary phase is the key point in any gaschromatographic separation; for this reason during the last decades, numerous efforts have been devoted toward the development of GC stationary phases capable of providing high resolution and efficiency, specific selectivity and, above all, high thermal stability. Recently ionic liquids (ILs) have been evaluated for this purpose. ILs represent a class of organic non molecular solvents that are liquid at 20°C, consisting of an organic cation containing N or P (i.e., alkylimidazolium, phosphonium) counterbalanced by an anion of organic or inorganic nature. Their specific properties, such as low volatility, good wetting ability on the inner walls of silica tubing and impressive thermal stability, make this class of compounds suitable as GC stationary phases. In this contribution, an overview of the evaluation as well as different applications of ILs stationary phases is presented. A scale of polarity has been developed In order to classify ILs according to McReynolds classification system. An highly polar ILs column was employed for the separation of C18 fatty acid cis/trans isomers and for the quali-quantitative determination of FAMEs in biodiesel blends. Further applications regard the analysis of flavour and fragrance compounds: a medium–high polarity ILs column, was evaluated and applied to the analysis of essential oils in conventional GC and to the determination of allergenes in perfumes by means of a GCxGC system. The results obtained showed the great potential and in some cases the superiority of ILs over well-established stationary phases.