Complexometrische EDTA-titratiecurven

An EDTA titration curve plots the metal ion concentration as the p function against the EDTA volume.

Before the equivalence point, the free metal ion is in excess. After the equivalence point, EDTA is in excess.

At and after the equivalence point, the free metal ion concentration is calculated using the conditional formation constant of the metal–EDTA complex.

The shape of the titration curve is influenced by the favorability of forming the complex. Consider the EDTA titration curves of calcium and strontium at pH 10.

A larger conditional formation constant corresponds to a larger decrease in the metal ion concentration, making a sharper break at the equivalence point.

Since the conditional formation constant is pH-dependent, so is the shape of the curve. Consider the titration of calcium with EDTA at various pH levels.

At a lower pH, the formation of the calcium–EDTA complex is less favorable, producing a less sharp break.

A higher pH favors the formation of the calcium–EDTA complex, providing a sharper break at the equivalence point.