Multivariate curve resolution with alternating least squares optimisation:: a soft-modelling approach to metal complexation studies by voltammetric techniques

Voltammetry of metal ions in the presence of ligands is usually interpreted by means of hard-modelling approaches. Soft-modelling approaches have been scarcely applied to electroanalytical data, especially in comparison with their use in spectroscopy. In recent years, the multivariate curve resolution-alternating least squares (MCR-ALS) method, based on factor analysis, has been shown to be a powerful tool in the analysis of metal complexation processes by a variety of voltammetric techniques. In this article, an overview of the method and its applications is presented. For this purpose, either numerically simulated or experimental data corresponding to different characteristic systems are analysed. A very interesting feature of MCR-ALS is that, by using different constraints, both the pure voltammograms of the different electrochemical processes involved and the corresponding concentration profiles are easily obtained. This type of information cannot be reached by means of classical univariate data analysis techniques. From calculated concentration profiles, the model of complexation and the equilibrium stability constants ave estimated. (C) 2000 Elsevier Science B.V. All rights reserved.