ANODIC-OXIDATION OF CYSTEINE CATALYZED BY NICKEL TETRASULFONATED PHTHALOCYANINE IMMOBILIZED ON SILICA-GEL MODIFIED WITH TITANIUM(IV) OXIDE

A chemically modified electrode constructed by mixing nickel tetrasulf onated phthalocyanine (NiTsPc) immobilized on modified silica gel with carbon paste showed a redox process with a midpoint potential of 0.44 V vs see. Experiments carried out with different supporting electroly tes suggested an effect due to the nature of the anion. The solution p H does not affect the midpoint potential but the peak current increase s when the pH is decreased. The immobilization procedure causes an inc rease in the monomeric form of the complex. The electrochemical proper ty of NiTsPc adsorbed onto modified silica showed good stability even in acidic media (pH = 2) and the ability to catalyze the electro-oxida tion of cysteine at 0.5 V vs see. (C) 1998 Elsevier Science Ltd. All r ights reserved.