Cathodic stripping voltammetry of the copper–1,10‐phenanthroline complex

Abstract

Cathodic stripping voltammetry of copper, based on the accumulation and reduction of its complex with 1,lO-phenanthroline (phen), has been studied. The complex is reduced in two steps from Cul-phen and Cu"-phen to copper amalgam at potentials of -0.43 and -0.62V vs. Ag/AgCl, respectively. The reduction processes are strongly dependent on the pH of the solution, as well as on the concentration of the metal ion and ligand. The reduction mechanism of both complexes was established. The detcction limit for copper in 0.55mol/LNaC1 with 20min accumulation at 0.OV vs. Ag/AgCI, measuring the reduction peak of the Cut-phen complex at -0.43 V vs. Ag/AgCI by SWV, was found to be about 5 x 10-lomol/L. The reaction parameters were calculated by square-wave voltammetry (SWV), i.e., transfer coefficients aCu~.phen = 0.31 and N~~I I .~~~~ = 0.45, and the maximum surface concentrations rCu~.phen = (2.02 f 0.08) x lo-" mol/cm2 and ~,-"II phen = (2.83 i 0.12) x lo-'* rnol/cm2. Measurements of the copper content in natural seawater samples were performed as well.

Tuning Electrochemical Bistability by Surface Area Blocking in the Cathodic Deposition of Copper

“…On the other hand, the electrons transfer in the metallic complex happens in an adsorption pathway in our electrochemical mechanism, asterisk means free active sites on the surface. The nature of the adsorbed complex is still not clear but experimental evidences in different substrates, concentrations, and solution pH have shown to be [Cu­(I)­(Phen) 2 ] + (ad) . − Nevertheless, in very strong acidic media as ours, the protonation of the nitrogen in the Phen molecules is energetically favorable. Because of the positively charged reactants, the formation of the coordinated bonds is not easily performed and a complex dissociation would occur as well.…”

“…This reaction intermediate has a short-lived state, and it is rapidly reduced to metallic Cu in lower potentials 78,79 Then, larger concentrations of Phen result in steeper slopes j vs E during the inhibition process and a shift to less negative potentials. As the dynamic equilibrium of the reaction r5 has an impact on the total coverage of the adsorbed metallic complexes, the mass variations would be associate mainly with the electrochemical deposition of Cu (the reduction evolving a metallic complex should shift the onset potential, but it is not verified in our experiments).…”

“…Naturally, the formation of the NDR is severely dependent on the pH, being its appearance facilitated when pH increases. 45 This reaction intermediate has a short-lived state, and it is rapidly reduced to metallic Cu in lower potentials 78,79…”

Implementation of a chemical equilibrium constraint in the multivariate curve resolution of voltammograms from systems with successive metal complexes

“…In fact, this reagent has been proposed for the determination of Cu(II) by adsorptive stripping voltammetry through the formation of adsorbed complexes. 14,15 The use of RPP decreases the interferences from adsorption and produces normal-shaped sigmoidal polarograms. However, the RPP signals measured in this system are affected by a very poor signal-to-noise ratio.…”

Influence of the HEPES Buffer on Electrochemical Reaction of the Copper(II)-Salicylaldoxime Complex

“…The determination of the concentration levels of copper ion in natural waters by CSV using a ligand such as: catechol [4], 8-hydroxyquinoline (oxine) [5], tropolone [6], 1,10-phenanthroline [7], and salicylaldoxime (SA) [8] is described. A so-called synergetic adsorption was achieved using mixed ligand systems such as 1,10-phenanthroline-tributylphosphate, as well as 2-thenoyltrifluoroacetone-tributylphosphate [9][10][11][12].…”