Three IL-based GC columns were used: Bis4MPyC6 (30 m, 0.22 mm×0.2 μm), Bis2MPyC9 (25 m, 0.22 mm×0.2 μm), Hex4MPy (18 m, 0.22 mm×0.2 μm). The structures of IL used in these columns are shown in Fig. . IL were prepared according to the procedure from Ref. . Cations (in the form of bromide) were prepared by heating a mixture of corresponding methylpyridine and bromo-or dibromoalkane at 120 °C during 2-6 hours. IL were prepared by the reaction of previously produced bromide with lithium bis(trifluoromethanesulfonyl)imide. The columns were prepared by the static high pressure technique at a constant temperature of 210 °C using tert-butanol as a solvent. The column preparation procedure is described in Ref. .