Analysis of a Pb(II) Unknown via Standard Addition

Experiment:

In this experiment you use Anodic Stripping Voltammetry (ASV) to determine the concentration of Pb(II) by the method of standard addition. ASV is commonly used for the determination of metal ions at trace levels because of its excellent detection limit (typically 10-9 to 10-12 M).

During the first step of the determination, the analyte together with Hg(II) is deposited via reduction to its elemental form at the working electrode by controlled potential electrolysis in a stirred solution. In the second step, the stirring is turned off and the potential of the electrode is scanned so that the deposited lead and then mercury are oxidized back to their ionic forms, i.e. anodically stripped from the electrode back into solution.

A computer controlled CH Instruments Electrochemical Analyzer 620A is utilized in a three-electrode setup with a glassy carbon working electrode, a Ag/AgCl reference electrode, and a platinum counter electrode.