Irreversible reactions:

Several electrode reactions are partially or totally irreversible

O + ne^- → R

The polarogram acquire in such cases is a drawn-out and less well defined. The polarographic equation for such reaction is

E = E_1/2- (0.05915/ αn) log i/i_d - I

here α is transfer coefficient and accounts for the kinetics of the electrode process.

Even in many electrode processes diffusion current is proportional to concentration and therefore, can be used for quantitative analysis. However, E_1/2 slightly varies with concentration of electro-active substance in the solution.