Adsorption behavior of amino acids on a stainless steel surface

The adsorption behavior of various amino acids on a stainless steel surface was investigated at 30 degrees C and over a pH range of 3-10. Acidic and b asic amino acids except histidine adsorbed remarkably at pH 3-4 and 7-10, r espectively, and showed Langmuir-type adsorption isotherms. The effects of pH and ionic strength on the adsorption isotherms were investigated to anal yze the interactions between amino acids and adsorption sites on the stainl ess steel. Hydrophobic amino acids and glycine showed only small adsorbed a mounts at all pHs tested. For the acidic and basic amino acids, reversibili ty of the absorption and the influence of the ionic strength on the adsorpt ion behavior were examined. The adsorption isotherms of the derivatives of aspartic acid were also measured in order to examine the contribution of th e carboxylic groups of acidic amino acids to the adsorption. Furthermore, a Fourier-transform infrared spectroscopic analysis and semiempirical molecu lar orbital calculation were carried out to analyze the ionization states a nd the configuration of the amino acids adsorbed on a stainless steel surfa ce. These investigations suggest that the acidic and basic amino acids adso rb through two electrostatic interactions of two ionized groups in the amin o acid with a stainless steel surface, (C) 2000 Academic Press.