Journal of Electroanalytical Chemistry, Vol.570, No.1, 69-75, 2004
Scanned stripping chronopotentiometry of metal complexes: lability diagnosis and stability computation
A method is presented for analyzing the dynamic speciation features of metal complexes based on stripping chronopotentiometry at a scanned deposition potential (SSCP). The shift in the SSCP half-wave deposition potential, DeltaE(d,1/2), is straightforwardly related to the complex stability, K, irrespective of the degree of lability; the limiting wave height, tau*, quantifies the metal species accumulated in the electrode and thus depends on both the lability and mass transport properties of the metal complex species in solution. For complexes with a lower diffusion coefficient than the free metal ion, K calculated from DeltaE(d,1/2) will be the same as that derived from the relative tau* values so long as the system is fully labile. Discrepancies between DeltaE(d,1/2)-derived and tau*-derived K values indicate loss of lability. We show that this approach is a sensitive indicator of lability, as illustrated by analysis of cadmium and lead binding by carboxylated nanospheres. (C) 2004 Elsevier B.V. All rights reserved.
Keywords:lability;stripping chronopotentiometry;scanned potential;SSCP;kinetic currents;trace metals;dynamic speciation