Abstract: The adsorption effects in ion-exclusion chromatographic separation of formic, acetic,propionic, iso-butyric, butyric, iso-valeric and valeric acids have been studied. It isassumed that both Donnan membrane equilibrium and adsorption equilibrium are involvedin chromatographic process. Thus, the following equation expressing the distribution coef-ficient, K_d, can be derived when water is used as an eluent: K_d=(K+1){[1+4(2+K)C/K_a]^1/2-1)/(2K+3+[1+4(2+K)C/K₂]^1/2)where K, K_a and C are adsorption equilibrium constant, dissociation constant and acid con-centration at peak maximum respectively.The adsorption equilibrium constants of some fatty acids are estimated from the reten-tion data. Linear relationship between lnK and topological parameters, ¹x are observed.

Key words: Ion-exclusion chromatography, Aliphatic acids, Adsorption