An eluotropic series is listing of various compounds in order of eluting power for a given adsorbent. The “eluting power” of a solvent is largely a measure of how well the solvent can "pull" an analyte off the adsorbent to which it is attached. This often happens when the eluent adsorbs onto the stationary phase, displacing the analyte. Such series are useful for determining necessary solvents needed for chromatography of chemical compounds. Normally such a series progresses from non-polar solvents, such as n-hexane, to polar solvents such as methanol or water. The order of solvents in an eluotropic series depends both on the stationary phase as well as on the compound used to determine the order.
| Adsorption Strength (Least Strongly Adsorbed -> Most Strongly Adsorbed) | ||||||||
|---|---|---|---|---|---|---|---|---|
| Saturated hydrocarbons; alkyl halides | Unsaturated hydrocarbons; Alkenyl Halides | Aromatic Hydrocarbons; Aryl Halides | Polyhalogenated Hydrocarbons | Ethers | Esters | Aldehydes and Ketones | Alcohols | Acids and Bases (Amines) |
| Eluting Power (Least Eluting Power -> Greatest Eluting Power) | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Hexane or Pentane | Cyclohexane | Benzene | Dichloromethane | Chloroform | Ether (anhydrous) | Ethyl Acetate (anhydrous) | Acetone (anhydrous) | Ethanol | Methanol | Water | Pyridine | Acetic Acid |
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“History is nothing but a procession of false Absolutes, a series of temples raised to pretexts, a degradation of the mind before the Improbable.”
—E.M. Cioran (b. 1911)