10.10 : 電位差滴定: 概要

Potentiometric titrations determine the concentration of an analyte by measuring the potential difference between the reference and indicator electrodes in the solution following the addition of the titrant.

A sudden change in the titration curve, which is obtained by plotting the potentials against the titrant volume, indicates the end point of the titration.

Additionally, the endpoint can be more precisely identified from the maximum of the first derivative curve or the zero point from the second derivative curve.

Potentiometric titrations can involve acid–base, precipitation, complexometric, or redox reactions.

Acid–base titrations typically use glass electrodes to measure pH, which is plotted against titrant volume to identify the endpoint.

Precipitation titrations measure the potential derived from concentration changes in the anion or cation due to precipitation with an ion-selective electrode via the Nernst equation.

Ion-selective electrodes are also used in complexometric titrations to record the change in metal-ion concentration as a function of added complexing ligands such as EDTA.

Redox titrations employ inert metal electrodes, like platinum. Plotting the potentiometric titration curve alongside curves from different visual indicators helps develop an alternative visual indicator to potentiometric titration.