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 (-Delta G) 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) -Delta G values were negative and K < 1, thus showing very low adsorption. Influence of the structure of the cc-substituent on adsorbability is analyzed. A linear dependence of -Delta G on the number of aliphatic carbon atoms was shown for the series: glycine-alanine-valine-leucine-isoleucine.