Voltammetric Characterization of Cu(II) Complexation in Real-Time

Aqueous metal behavior is strongly regulated by speciation, which in turn is highly dependent on complexation. Trace metal complexation is difficult to characterize in dynamically changing systems due to a lack of analytical methods that can rapidly report free-metal concentrations. In this paper, we perform proof-of-principle experiments that demonstrate the utility of fast-scan cyclic voltammetry (FSCV) for providing speciation information in real-time by characterizing dynamic Cu(II) binding. We study Cu(II) FSCV responses in 3-(N-morpholino)propanesulfonic acid (MOPS) buffer and characterize the hydrodynamic aspects of our experimental setup (continuously stirred tank reactor). We observe Cu(II) complexation in real-time using five ligands with differing formation constants of Cu(II) complexation. Finally, we utilize geochemical models to fit our real-time experimental Cu(II)-binding curves. Our proof-of-principle experiments show that FSCV is a powerful tool for studying real-time Cu(II) complexation, which is essential speciation information for better interpretation of Cu(II) behavior in dynamically changing systems, such as those encountered in biology or the environment.