Developing Ionic Liquid-based Stationary Phases for Comprehensive Two-Dimensional Gas Chromatography

Multidimensional gas chromatography (MDGC) is an extremely valuable tool for the separation, detection, and identification of volatile and semi-volatile constituents in many complex samples. A typical MDGC separation employs two or more gas chromatographic separations in a sequential fashion. In order to achieve a significant improvement in resolution power, the stationary phases employed often possess different selectivities. Until recently, commercial poly(siloxane)- and poly(ethylene glycol)-based stationary phases have been widely applied in MDGC separations. However, their solvation characteristics and thermal stabilities are often limited for particular classes of compounds, such as those complex mixtures often found in the petrochemical industry.

Using the Abraham solvation parameter model as a guiding tool in the structural design of ILs, we have developed low cohesive phosphonium-based IL stationary phases for comprehensive two-dimensional gas chromatography (GC×GC). These new statationary phases were used for the first time as the second dimension column (HP-5 × IL) in the separation of aliphatic hydrocarbons in kerosene. These compounds were the first reported class of ILs that were capable of resolving the aliphatic hydrocarbons (see chromatograms below) while also possessing high thermal stabilities (up to 320°C). On-going studies within the group are focused on understanding the structural attributes of the IL that provide the observed enhanced selectivity and using this knowledge in the development of new classes of stationary phases for applications within the petrochemical, flavors and fragrance, and pharmaceutical industries.