Abstract
The effect of chain length of alkyl bonded phases on adsorption characteristics, especially mass transfer phenomena and thermodynamic parameters, in reversed-phase liquid chromatography was studied by the chromatographic method and moment analysis. Adsorption equilibrium constant, isosteric heat of adsorption and activation energy of surface diffusion increased with an increase in length of alkyl ligands in short chain regions. On the contrary, surface diffusion coefficient increased with a decrease in alkyl chain length. Change of all the parameters decreased when the carbon number of the alkyl ligands was about 8 and above. Almost the same adsorption characteristics were observed when C8 and C18 packing materials were used as an adsorbent, It is concluded that only parts of long alkyl chains contribute to adsorption phenomena in reversed-phase liquid chromatography. The contribution of surface diffusion to intraparticle diffusion was significant and increased with an increase in alkyl chain length.
