Voltammetric methods for distinguishing between dissolved and particulate metal ion concentrations in the presence of hydrous oxides. A case study on lead(II)

Voltammetric techniques (differential pulse polarography, DPP, anodic stripping voltammetry, ASV, and differential pulse anodic stripping voltammetry, DPASV) were evaluated for their capability to distinguish between dissolved and particulate Pb(II) concentrations. Colloids of FeOOH, MnO2, and SiO2 were found to have no effect on the electrochemical reversibility (peak width, peak potential, and pseudopolarographic half-wave potential) of the Pb(II) reduction system. Soluble Pb(II) concentrations measured in the presence of colloids were consistent and independent of the voltammetric method used and the different time scales employed in these techniques. Equilibrium constants for the specific adsorption of Pb2+ on FeOOH, MnO2, and SiO2 surfaces were determined. Applicability of voltammetric techniques to other metals and in the presence of other colloids and in natural waters is discussed.