Incorporation of Imidazolium Ionic Liquids in GC Stationary Phases via the Sol–Gel Process
Résumé
Room-temperature ionic liquids (RTILs) have proven to be efficient polar or highly polar stationary phases for GC. Nevertheless, the thermal stability of monocationic RTILs limits their use in high-temperature GC. To improve the thermal stability, an RTIL based on a 1-methylimidazolium derivative was anchored in a three-dimensional network using the sol-gel process. Three different strategies were compared: using the derivative pure, in combination with a polymer or copolymerised with diethoxydimethylsilane. This last method allowed for the preparation of hybrid stationary phases with satisfactory efficiency (3500 plates per meter determined by the injection of n-tetradecane at 80 °C, k = 8.19) and very good thermal stability up to 340 °C using the NTf2 counter ion. The stationary phases demonstrated a good ability to separate positional isomers and polycyclic aromatic hydrocarbons. Polarity and molecular interactions with analytes were characterized by calculating the Rohrschneider-McReynolds constants and Abraham system constants. A classification of the polarity of the new stationary phases relative to 44 stationary phases, including commercial and non-commercial ones, was performed based on the RTILs using principal component analysis. Finally, the maximal operating temperature of these new stationary phases was compared with those of the most thermally stable conventional or RTIL-based stationary phases, demonstrating that the