The selectivity of the considered stationary phases significantly differs from the selectivity of polyethylene glycol. The retention on ionic liquids cannot be directly computed using only the retention index on polyethylene glycol. However, the retention index on polyethylene glycol predicted using a machine learning model (trained on other, non-overlapping data) is a very good descriptor for predicting retention indices on ionic liquids. Sufficiently accurate linear models for retention index prediction were developed for these stationary phases.