Three-dimensional voltammetry assisted by parametric signal fitting: a new perspective for the electrochemical evaluation of metal binding in the presence of electrodic adsorption.

A new perspective of three-dimensional voltammetry is given for the study of metal complexation in the presence of adsorption phenomena and, eventually, when the electrochemical reversibility of the processes decreases. For this purpose, 3D-voltammograms are obtained as usual, i.e.

Application of different chemometric strategies to voltammetric and UV-vis spectroscopic data to obtain a complexation model: study of the Cu(II) binding with the phytohormone 6-benzylaminopurine.

The complexation processes of Cu(II) by the phytohormone and the possible antitumoral agent 6-benzylaminopurine (BAP) were studied by Differential Pulse Polarography (DPP) and ultraviolet-visible spectroscopy (UV-vis) in combination with chemometric programs such as Multivariate Curve Resolution by Alternating Least-Squares (MCR-ALS) and Gaussian Peak Adjustment (GPA). All data confirm the formation of the predominant 1 : 1 and 1 : 2 Cu(2+) : BAP complexes. The corroboration of the presented stoichiometries was performed by ElectroSpray Ionization-Mass Spectrometric (ESI-MS) experiments of the Cu(II)-BAP system at different ratios.

Bismuth film electrodes for the study of metal thiolate complexation: an alternative to mercury electrodes.

A comparative study of the usual static mercury drop electrode (SMDE) and the bismuth film electrode (BiFE) as applied to the analysis of metal complexation by thiol-rich peptides is done. Preliminary experiments on BiFE by differential pulse voltammetry showed that Cd(II) and Pb(II)-ions behave in a similar way as using stripping voltammetry and stripping chronopotentiometry with regard to some splitting effects of the signals. Additionally, on BiFE glutathione (GSH) and some phytochelatins (PC(n)) produce quite irregular signals related to the anodic oxidation of bismuth, which restricted the studies to a narrower concentration range than on SMDE.

Combined use of the potential shift correction and the simultaneous treatment of spectroscopic and electrochemical data by multivariate curve resolution: analysis of a Pb(II)-phytochelatin system.

The combined use of differential pulse polarography (DPP), circular dichroism (CD) and multivariate curve resolution by alternating least squares (MCR-ALS), with potential shift correction for data analysis, provides valuable information on the complexation of Pb(ii) by the phytochelatin (gamma-Glu-Cys)(3)-Gly (PC(3)). All data confirm the formation of the predominant 1 : 1 Pb-PC(3) complex. However, in the presence of an excess of Pb(ii), the same complex seems to be present but with some modification in its structure.

Potential shift correction in multivariate curve resolution of voltammetric data. General formulation and application to some experimental systems.

A new mathematical algorithm is proposed to correct the progressive potential shift of some voltammetric signals that decrease the linearity of the data. The corrected data matrix can be further analysed by Multivariate Curve Resolution by Alternating Least Squares (MCR-ALS) and the vector including the potential shift corrections can be fitted to specific equations such as that by DeFord-Hume. A detailed discussion is given on the different cases of potential shift correction, and, in some of them, mathematical simulation is made or experimental systems [Cd(ii)-glutathione and Zn(ii)-glycine] are analysed.

Multivariate curve resolution applied to the simultaneous analysis of electrochemical and spectroscopic data: study of the Cd(II)/glutathione-fragment system by voltammetry and circular dichroism spectroscopy.

Multivariate curve resolution with alternating least squares (MCR-ALS) is applied for the first time to the simultaneous analysis of electrochemical and spectroscopic data. Then, a data analysis is done with augmented matrices constituted by Differential Pulse Polarography and Circular Dichroism data submatrices. The use of proper, and different for each submatrix, constrains in the iterative ALS optimization allows to obtain chemically meaningful results constituted by a common matrix containing the concentration profiles, and two matrices with the pure electrochemical and spectroscopic signals.

Soft modelling for the resolution of highly overlapped voltammetric peaks: application to some Pb-phytochelatin systems.

A differential pulse polarographic (DPP) study of the Pb(2+)/Cys-Gly, Pb(2+)/gamma-Glu-Cys, Pb(2+)/PC(2) and Pb(2+)/PC(3) systems is performed, being PC(2) and PC(3) the phytochelatins of general structure (gamma-Glu-Cys)(n)-Gly, with n=2 and 3, respectively. Analysis of DPP data is assisted by multivariate curve resolution with alternating least squares (MCR-ALS) method in order to establish the complexes formation sequence and their final stoichiometries. DPP signals of these systems present, besides overlapping of peaks due to free metal ion and metal complexes, interference of mercury anodic signals.