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These stationary phases, developed more recently than the previous ones, are made of di‐ or tri‐cationic salts (ammonium or phosphonium) associated with sulfonate‐ or imide‐type organic anions (Figure 2.8). For GC, we use viscous ionic liquids with a melting point lower than ambient temperature, due to the fact that these are stable from a heating standpoint and not very sensitive to oxygen. These polar phases, deposited and not grafted on the column surface, are suitable for the analysis of neutral, basic or diverse compounds (fatty acid esters). Elution diagrams are different from those obtained with Carbowax, which makes them useful in two‐dimensional GC. Their near‐zero vapour pressure makes them useful for GC‐Mass Spectrometry.

Figure 2.8 Polarity scale of stationary phases in GC and summary of the three types of stationary phase. The polarity scale goes from squalane (polarity 0 by definition) to polarity 100 for TCEP (tricyanoethoxypropane). (a) Polysiloxane structure (silicones), (b) polyethylene glycols. Many phase compositions of this type, used in impregnation or grafting. (c) e.g. a dicationic tetraalkylphosphonium type ionic liquid associated with an imide (here, IL60); max. temperature 300°C.