Fast voltammetry of metals at carbon-fiber microelectrodes: towards an online speciation sensor

Abstract

Speciation controls the chemical behavior of trace metals. Thus, there is great demand for rapid speciation analysis in a variety of fields. In this study, we describe the application of fast scan cyclic voltammetry (FSCV) and fast scan adsorption controlled voltammetry (FSCAV) to trace metal speciation analysis. We show that Cu²⁺ can be detected using FSCAV in different matrices. We find that matrices with different Cu²⁺ binding ability do not affect the equilibrium of Cu²⁺ adsorption onto CFMs, and thus are an excellent predictor for free Cu²⁺ ([Cu²⁺]_free) in solution. We modelled a correlation between the FSCV response, [Cu²⁺]_free and log K_f for 15 different Cu²⁺ complexes. Using our model, we rapidly predicted, and verified [Cu²⁺]_free and K_f of a real groundwater sample spiked with Cu²⁺. We thus highlight the potential of fast voltammetry as a rapid trace metal speciation sensor.