Characterization of a dicationic imidazolium-based ionic liquid as a gas chromatography stationary phase

- A new dicationic imidazolium-based ionic liquid (IL) stationary phase has been synthesized.
- The McReynolds constants, Abraham solvation parameters, and the activity coefficient at infinite dilution were calculated.
- The IL is liquid at room temperature and has high thermal stability up to 420 °C.
- The ionic liquid is a good choice for the separation of a wide range of analytes, especially poly aromatic compounds.

Here we report the characteristics of a new synthesized ionic liquid, 1,9-di(N-naphthalen-2-ylimidazolium)nonane bis[(trifluoromethyl)sulfonyl]imide ([C9(2NPTim)2][(NTf2)2]), as a stationary phase by inverse gas chromatography. The McReynolds constants demonstrated that the [C9(2NPTim)2][(NTf2)2] had an average polarity of 667 and polarity number P.N. = 75, suggesting its polar nature. The solvation properties of the new stationary phase were determined by the calculation of Abraham solvation system constants, whereby the results showed that its major interactions with the analytes included H-bond basicity (a), dipole-dipole (s) and dispersive (l) interactions. The activity coefficients (γ∞) and selectivities (SIJ∞) at infinite dilution were also determined for various polar and nonpolar organic solutes at different temperatures. The separation performance of the [C9(2NPTim)2][(NTf2)2] stationary phase was evaluated by GC separations of different analytes, including normal alkanes and aromatic compounds. The TGA results showed that the stationary phase had high thermal stability up to 420 °C.