Kinetic determination of EDTA and citrate by the displacement of fluoride from Al 3+F − complexes and use of a fluoride ion-selective electrode

Abstract

The displacement of fluoride from its aluminium complexes by the action of EDTA, citrate and other ligands is a relatively slow process which can be monitored potentiometrically with a fluoride ion-selective electrode. Some characteristics of these reactions are presented. There is evidence that [AlF] 2+ reacts with the competitive ligand faster than the simple free (hydrated) Al 3+ species does. The relative rates of release of fluoride by the action of various aminopolycarboxylic acids have been determined. Potentiometric reaction-rate methods have been developed for the determination of 0.2–1.5 μmole of EDTA and 0.1–1.0 μmole of citric acid, with average relative errors of ∼3%.