Markitan O. Adsorption of biogenic amines and relative compounds onto fumed silica surface

Dissertation is devoted to the study of adsorption of biogenic amines and their related com-pounds (amino acids and dipeptides) on the silica surface from aqueous solutions. The adsorption of biogenic amines and related compounds from aqueous solution onto silica surface is investigated in dependence on pH, ionic strength of solution, and adsorbate concentration. It has been found that biogenic amines are adsorbed due to the electrostatic interaction between ion-ized silanol groups of silica and protonated amine forms with surface complex formation. Only ba-sic amino acids and related dipeptides are adsorbed onto fumed silica surface due to the electrostatic interaction between ionized silanol groups and additional basic functional groups of biomolecules. The binding constants of biomolecules with surface silanol groups are calculated using basic Stern model and GRFIT program. The stability of surface complexes can be increased due to hydrogen bond formation between their protonated forms and water molecules in near-surface layer or with silanol groups. The effect of copper ions on the adsorption of histamine and basic amino acids onto fumed silica surface has been studied. It has been shown that formation of complex species in solution determines the character of adsorption of these biomolecules. The stability constants of ternary surface complexes, in which the silanol groups play role as one of the ligands, are calculated. The adsorption of biogenic amines - tryptamine and tyramine from water solution onto silica modified by bovine serum albumin are investigated as a function of pH and adsorbate concentration. It has been shown that modification of silica surface with albumin leads to expansion of the pH range in which the amine adsorption occurs. The adsorption of some biogenic amines, amino acids and dipeptides onto silica surface modified by macrocyclic polyether dibenzo-18-crown-6 has been studied. The binding constants of biomolecules with crown ether attached to the surface are calcu-lated from their adsorption isotherms. The stability of surface complexes is determined by different types of interaction: stacking between aromatic rings, hydrogen bond formation between amino groups of adsorbates and oxygen atoms of macrocycle cavity.