Metal speciation controls the behavior of aqueous metal ions. Fundamental thermodynamic parameters, such as the formation constant (Kf) of metal–ligand equilibria, provide useful speciation information. Although this information can be determined by spectroscopic techniques with high accuracy, it comes at the expense of time and cost. In this work, we studied Cu(II) complexation with different ligands using an ultra-fast method, fast scan cyclic voltammetry (FSCV) at carbon-fiber microelectrodes (CFMs). We observed a correlation between the FSCV response and the previously reported Cu(
II)–ligand equilibrium constants. This relationship allowed us to model a predictive relationship between Kf and 16 model ligands. We hence present an essential proof of principle study that highlights FSCV's capability to prove speciation information in real time. To read the rest of the article click here.