In this work, four ionic liquids (ILs) based on the N-alkyl-N-methylmorpholinium cation ([Mor1,R], in which R = 2, 4, 8, or 10) and bis(trifluoromethanesulfonyl)imide anion were synthesized. Using GLC, a number of parameters describing the sorption properties of the investigated ILs were determined. The values of Kovats indices, McReynolds constants, and activity coefficients at infinite dilution were the basis for the evaluation of intermolecular interactions. The effect of the chain length of the alkyl substituent in the cation, which was used to modify their polarity, has been discussed. Comparison of the characteristics of the investigated IL-based stationary phases with commercially available ones allowed for the statement that the investigated ILs were more polar. The tested ILs had a relatively high polarity. Increasing the length of the alkyl chain in the morpholinium ring reduced polarity. ILs based on the morpholinium cation were tunable in a wide range of their polarity.