Liquid chromatographic evaluation of equilibrium and kinetic parameters of large molecule amino acids on silica gel

Abstract

Sorption and diffusion of four large-molecule amino acids (glutamine, methionine, phenylalanine, and tryptophan) in a uniform pore size silica gel adsorbent have been studied by the chromatographic method. All four species were adsorbed quite rapidly but with significant differences in both pore diffusivity and equilibrium constant. The diffusivities show a regular decrease with increasing molecular weight, but the variation in equilibrium constants and heats of sorption was less regular. Tortuosity factors calculated from the pore diffusivities are consistent with a molecular diffusion mechanism with some evidence of steric hindrance for the larger molecules. The potential of such adsorbents as a means of separating amino acids is briefly considered.