The Advent and Potential Impact of Ionic Liquid Stationary Phases in GC and GCxGC

Choices of available stationary phases for gas chromatography (GC) have been fairly constant for many years. The same basic types of columns that do analogous separations can be obtained from any of a large number of sources, worldwide. Recent research has indicated that unique new substances have been developed that will play an important role in GC column technology. These substances are ionic liquids (ILs). ILs are solvents in which the constituents consist entirely of ions. By definition, they are pure salts that have melting points below 100 °C. However, when used as GC stationary phases, melting points in the range of ~ –40 °C to 50 °C are preferable. ILs have a number of properties that make them exceptional stationary phases. For example, their viscosity can be varied over a broad range, they can have high thermal stabilities, they can be coated on fused-silica capillaries with high efficiencies, they have unique solvent properties and they can be immobilized and crosslinked.1–7 Indeed, it was noted early on that IL stationary phases had a dual nature in that they separated nonpolar analytes as if they were nonpolar stationary phases and simultaneously separated polar analytes as if they were polar stationary phases.8