Multistep controlled potential electrolysis:

Determination of several metal ions in the same solution is possible along with controlled potential electrolysis using mercury pool cathode. A sample solution containing various metal ions such as Cu²⁺, Bi³⁺, Pb²⁺ and Zn²⁺ could be analyzed through controlled potential analysis.  Whenever the cathode potential is controlled at about + 0.008 vs. SCE, Cu²⁺   is decreased to Cu⁰. While the current decays to zero, then the potential could be controlled so in which Bi³⁺ could be reduced to Bi⁰. Following through controlling the potentials, Pb²⁺ could be determined as Pb⁰ and Zn²⁺ as Zn. A sample of brass/bronze which contains Cu²⁺, Zn²⁺, and Pb²⁺ could be analyzed through this technique.