Eluotropic series

An eluotropic series is a ranking of solvents or solvent mixtures (mobile phases) according to their ability to elute compounds from a stationary phase. Eluotropic series are used to select mobile phases for straight-phase chromatography.

Since the elution order depends not only on the stationary and mobile phase, but also on the compounds examined, there is no universal eluotropic series.
The most important factors are: The order of solvents differs slightly between authors, but alkanes (e.g. hexane) are consistently at one end, and water (and alcohols, acids and bases) at the other. The polarity of alcohols (as well as that of esters, ketones et c.) increases with decreasing chain length, i.e. methanol > ethanol > propanol.