Electrochemical Study of the Complexes of Aspartame With Cu(II), Ni(II) and Zn(II) Ions in the Aqueous Medium

Abstract

The voltammetric behaviours of aspartame in the presence of some metal ions (Cu(II), Ni(II), Zn(II)) were investigated. in the presence of aspartame, copper ions reduced at two stages with quasi-reversible one-electron and, with increasing the aspartame (L) concentration. Cu(II)L-2 complex reduces at one-stage with irreversible two-electron reaction ( -0.322 V). Zn(II)-aspartame complex (log beta = 3.70) was recognized by a cathodic peak at -1.320 V. Ni(II) -aspartame complex (log beta = 6.52) is reduced at the more positive potential ( -0.87 V) than that of the hydrated Ni(II) ions ( -1.088 V). In the case of the reduction of Ni(II) ions. aspartame serves as a catalyst. From electronic spectra data of the complexes, their stoichiometries of 1:2 (metal-ligand) in aqueous medium are determined. The greatness of these logarithmic values is agreement with Irwing-Williams series (Ni < Cu > Zn). (C) 2003 Elsevier Science Ltd. All rights reserved.