Potentiometric titration of metal ions in methanol

Abstract

The potentiometric titrations of nine lanthanideIII triflates, ZnII and CuII triflate, and the NiII, CoII, MgII, and TiIV perchlorates were obtained in methanol to determine the titration constants (defined as the sspH at which the [OCH3–]/[Mx+]t ratios are 0.5 and 1.5) as well as the apparent sspKa values for deprotonation of the metal-bound solvent molecules. The titrations were performed under various conditions with and without added salts as electrolytes, and the variations in the titration constants are discussed. In selected cases (La3+, Zn2+) the titration profiles were analyzed using a complex fitting program to obtain information about the species present in solution.Key words: potentiometric titration, methanol, sspH, metal ion, lanthanides, apparent sspKa.