Effects of adsorption in stripping chronopotentiometric metal speciation analysis

The effects of induced metal ion adsorption on speciation analysis by stripping chronopotentiometry (SCP) are examined and compared with those observed in stripping voltammetry (SV). SCP measurements performed under conditions approaching complete depletion (low stripping current) were found to have significant advantages: such measurements are essentially free from adsorption effects, and in addition, the requirement for excess ligand during the stripping step is minimised. In contrast, induced metal adsorption caused enhancement of SCP measurements performed under conditions of semi-infinite linear diffusion (incomplete depletion; high stripping current), DC-SV and DP-SV. We show that the adsorption effects for these shorter timescale techniques are in broad agreement with theoretical predictions, but rigorous analysis is precluded by the fact that adsorption is in some transient stage and thus varies both with time within the measurement period and with potential.