For the use in gas chromatography -mass spectrometry (GC-MS), SP should be particularly thermostable and non-volatile in order to provide low background noise. For less volatile, heavy, and polar analytes, the SP have to be stable at higher temperatures. In Ref. , it was demonstrated that some imidazolium-based IL can be used for GC-MS at temperatures up to 300 °C and have background noise considerably lower than polyethylene glycol-based SP (PEG) and comparable with the non-polar HP-5ms SP.