Quantitative polarographic analysis:
Polarographic analysis can be used among 10-3 to 10-5 M concentrations of electroactive substances. If solutions have more than single electroactive substance and if their half-wave potentials within a particular supporting electrolyte differ through about 0.4 V for single charged ions and 0.2 V for doubly charged ions they could be determined.
If the half-wave potential of two ions is close then several experimental devices could be employed. They involve
i) Precipitation of one (eg. Lead and Zinc mixture - lead might be removed as lead sulphate precipitate for the determination of zinc).
ii) Complexation: Through adding complexing agent, E1/2 of one of the ions might be shifted to more negative potential thereby ? E1/2 of ions becomes more. (eg.: Cu(II) ion can be complexed by potassium cyanide and thereby E1/2 is shifted to more negative potential than lead or cadmium).
There are three techniques that have been hugely used in practice. In all these methods oxygen is removed before taking polarograms of solutions.