Free energies of amino acid adsorption on silica in neutral aqueous medium as estimated from high-performance liquid-chromatographic retention data.

Equilibrium constants (K) and free energies (-ΔG) of amino acid adsorption on silica in a neutral aqueous medium were calculated from the retention values measured by means of high-performance liquid chromatography on a silica gel column. For most amino acids (with the exception of proline) -ΔG values were negative andK < 1, thus showing very low adsorption. Influence of the structure of theα-substituent on adsorbability is analyzed. A linear dependence of -ΔG on the number of aliphatic carbon atoms was shown for the series: glycine-alanine-valine-leucine-isoleucine.