Linear plots for complexometric potentiometric titrations of mixtures of two metal ions

Abstract

The application of Gran plots to potentiometric complexation titrations of mixtures of two metals with a selective electrode for one of the metal ions is surveyed. New developments are discussed; only 1:1 reactions are considered. Depending on the ratio between the conditional stability constants of the two metal chelates, the first and/or second equivalence point can be found by using different forms of approximately linear Gran functions. Criteria for identifying the linear range of Gran functions using logarithmic diagrams are illustrated. Rigorous equations for linearised titrations are introduced.