Polarographic methods using half-wave potentials are frequently used to evaluate complex ion systems. When the electrode reaction at the DME is reversible, calculation methods are simple. However, for non-reversible electrode reactions, calculations are usually relatively difficult and consequently polarographic methods are not commonly used to study systems involving non-reversible electrode reactions. In this work, the possibility of using the simple calculation method of plotting ΔE1/2 vs. the logarithm of the concentration of the ligand, for the class of the electrode reaction in which the non-reversibility of the electrode reaction is due to the charge transfer step and is independent of complex formation, has been investigated. The zinc-fluoride complex ion system has been studied by d.c., a.c. and rapid polarographic methods and the results have been used to assess the reliability and extent of applicability of the simple method of calculation proposed.