Stripping chronopotentiometry for metal ion speciation analysis at a microelectrode

The features of metal ion speciation determination by stripping chronopotentiometry (SCP) at a microelectrode are examined and compared with those of DP-SV. SCP measurements are essentially of a steady-state nature under experimentally achievable conditions and correspond to practically complete depletion of the microelectrode. SCP data for simple systems (pyridine-2,6-dicarboxylate complexes with Cd(II) and Pb(II)) and a heterogeneous system (Pb(II)–fulvic acid) were in general agreement with the recently developed theory that predicts reduced lability at microelectrodes due to enhanced diffusion. Furthermore, SCP measurements were not influenced by adsorption processes nor by the ligand-to-metal ratio at the electrode surface during stripping. In contrast, DP-SV data could not be interpreted in a straightforward manner due to (i) adsorption-induced enhancement of the stripping signals and (ii) severe peak distortion arising from saturation of the ligand at the electrode surface during stripping.