Metal complexation by electroanalytical techniques: hard- and soft-modelling approaches

vidual chemical element between different chemical species or groups of species [1]. In natural aquatic systems it reflects the chemical complexity of these media. Substantial progress has been made over recent years in chemical speciation and in the understanding of metal interactions with aquatic organisms, which are crucial issues owing to their intimate relationships with bioavailability and toxicity. In early studies, designed to measure trace metal toxicity, metal solution chemistry was generally overlooked. However, more recent work has stressed the importance of metal solution equilibria in controlling chemical speciation in the exposure medium external to organisms [1]. Metal complexation equilibria and speciation have been classical subjects of electroanalytical techniques, especially potentiometry and voltammetry. In recent years, interest in this subject has been renewed because of the increasing focus of Analytical Chemistry on metal speciation over total metal concentration determination. As mentioned previously, this is because the direct relationship of metal speciation with bioavailability and biouptake by microorganisms. In recent years several dynamic, in situ speciation techniques have been developed for routine use, although they CONTRIBUTIONS to SCIENCE, 2 (3): 359-373 (2003) Institut d’Estudis Catalans, Barcelona