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

A differential pulse polarographic (DPP) study of the Pb2+/Cys-Gly, Pb2+/γ-Glu-Cys, Pb2+/PC2 and Pb2+/PC3 systems is performed, being PC2 and PC3 the phytochelatins of general structure (γ-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. Despite these complications, MCR-ALS allows us to propose a model of complexation for each system, and some tentative structures for the complexes.