Potentiometric Titration
Also known as: potentiometry, electrochemical titration
Potentiometric titration is an electrochemical method of analysis that measures the potential difference between a reference electrode and an indicator electrode as a titrant is gradually added to a solution. Developed in the early 20th century, it allows precise determination of the concentration of analytes without requiring visual endpoint indicators. This method is fundamental in analytical chemistry for determining acids, bases, redox species, and metal ions.
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When to use it
Potentiometric titration is ideal for colored solutions (where indicator dyes are unsuitable), very dilute solutions (where visual indicators lack contrast), and analytes that do not form colored complexes. It is particularly valuable for redox titrations, metal-ion determinations using complexometric titrants, and determination of acids and bases in non-aqueous solvents. Use this method when an automated, objective endpoint determination is needed, or when the sample matrix or analyte properties make traditional visual titration impractical.
Strengths & limitations
- Objective endpoint determination eliminates subjective color judgment
- Applicable to colored, opaque, or turbid solutions
- High sensitivity for dilute analytes without signal loss from poor color contrast
- Adaptable to non-aqueous and mixed-solvent systems
- Amenable to automation and continuous monitoring
- Requires properly calibrated electrodes and regular maintenance
- Temperature-sensitive (electrode potential varies with temperature)
- Unsuitable for samples with very high ionic strength in some cases
- Initial investment in electrode apparatus higher than simple colorimetric methods
Frequently asked
What is the difference between potentiometric titration and traditional visual titration?
Visual titration relies on a color change near the equivalence point (indicator dye), making it subjective and unsuitable for colored solutions. Potentiometric titration measures the dramatic shift in cell potential at the equivalence point, providing an objective, instrumental endpoint determination that is less affected by solution color or turbidity.
How do I identify the equivalence point from a titration curve?
The equivalence point appears as the steep inflection point in the curve of potential versus titrant volume. Mathematically, it is located at the maximum of the first derivative (or zero of the second derivative) of the curve. Software can calculate this automatically, or you can estimate it visually as the steepest part of the S-shaped curve.
Why must electrodes be calibrated before use?
Electrode potential depends on the concentration of the ion being measured (Nernst equation). Calibration with standard buffer solutions establishes the exact relationship between potential and concentration (or pH) for your specific electrode, cell geometry, and temperature, eliminating systematic errors.
Can potentiometric titration be used in non-aqueous solvents?
Yes. Non-aqueous potentiometric titration is valuable for weak acids or bases that exhibit better differentiation (sharper breaks in the curve) in organic or mixed solvents than in water. Electrode selection and calibration procedures must be adapted for the solvent used.
What causes a slow or unresponsive electrode?
Slow response usually indicates a dry or fouled glass electrode membrane, a clogged reference electrode junction, or a depleted salt bridge. Regular hydration, gentle cleaning, and storage in appropriate solutions (distilled water for glass electrodes) maintain performance. Severely fouled electrodes may require replacement.
Sources
- Skoog, D. A., West, D. M., Holler, F. J., & Crouch, S. R. (2014). Fundamentals of Analytical Chemistry (9th ed.). Cengage Learning. ISBN: 978-1133170960
- Covington, A. K., Bates, R. G., & Durst, R. A. (1985). Definitions of pH scales, standard reference values, measurement of pH and related terminology. Pure and Applied Chemistry, 57(3), 531–542. DOI: 10.1351/pac198557030531 ↗
- Michels, H. H., & Sielcken, O. E. (1965). A potentiometric method for the determination of moisture. Journal of Applied Chemistry, 15(12), 589–594. link ↗
How to cite this page
ScholarGate. (2026, June 3). Potentiometric Titration. ScholarGate. https://scholargate.app/en/analytical-chemistry/potentiometric-titration
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