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Why Metrohm Karl Fischer titrators? – A long history of success
Karl Fischer titration is the preferred method for water content determination in pharmacopeias and countless norms, e.g. ASTM or DIN. Metrohm has been offering reliable solutions for Karl Fischer titration for more than 70 years. Ever since, the instruments have been continuously improved to meet the needs of the users.
- Get the complete range from compact benchtop solutions to modular automated systems including accessories and software for volumetric and coulometric Karl Fischer titration from one supplier.
- Rely on Swiss-made quality.
- Benefit from our global presence in over 80 countries for local support by our service and application experts.
Learn more about KF titration in more than 100 application notes written by our application specialists:
In addition to Karl Fischer titrators, Metrohm also offers a wide range of potentiometric titrators and a robust solution for process analysis.
Karl Fischer titrator – FAQs
What is Karl Fischer titration?
Karl Fischer (KF) titration is one of the most tried and trusted methods for measuring both free and bound water content. With the KF method, you can, for instance, determine the surface water on crystals as well as the water contained within the crystals. KF titration:
- can be used for moisture determination (i.e., water content determination) in all sample types: liquids, solids, slurries, and gases
- works over a wide concentration range from ppm up to 100%
- is fast and highly selective
- supplies reproducible and correct results
How does Karl Fischer titration work?
KF titration is based on two redox reactions. Using classical alcohol-based Karl Fischer reagents, the components methanol and sulfur dioxide form an alkyl sulfurous acid. In the presence of water and iodine, the alkyl sulfurous acid is oxidized in a water-consuming reaction. The reaction stops when all the water was consumed and a small excess of iodine indicates the endpoint of the titration.
Karl Fischer titration can be performed manually or fully automated. Metrohm offers various solutions:
- The OMNIS KF titrator can be extended by an OMNIS Sample Robot to perform up to four fully automated titrations at the same time with automated sample changing for non-stop titration: Go to automation options for OMNIS KF titrators
- The KF Titrando and the KF Ti-Touch offer the option to add automated thermal sample preparation for samples that cannot be titrated directly: Go to automation options for KF Titrando or KF Ti-Touch
Volumetric vs. coulometric Karl Fischer titration
Two different types of Karl Fischer titration exist: the volumetric method (volumetry) and the coulometric method (coulometry). The table below compares the two methods.
| Volumetric KF titration | Coulometric KF titration | |
|---|---|---|
| Moisture | 0.1% to 100% |
0.001% to 1% |
| Sample addition | solid or pasty samples can be added directly into the titration vessel (opening a volumetric titration cell for a short period of time does not falsify the results) liquid samples are added with syringe through a septum |
liquids or gases are added with syringe through a septum: to avoid ambient humidity to enter the titration cell, never open a coulometric cell |
| Titer determination | regularly | not necessary |
| Iodine addition/generation | iodine-containing titrant is added via buret | produced by a generator electrode by anodic oxidation |
Steps for volumetric titration:
- Filling of titration vessel with solvent
- Pre-titration (conditioning)
- Addition of sample (or water standard for titer determination)
- Titration with KF reagent
Steps for coulometric titration:
- Filling of titration vessel with solvent
- Pre-titration (conditioning)
- Addition of sample
- Titration with generated iodine
Further information
Application bulletin: Volumetric water content determination according to Karl Fischer
Application bulletin: Titer determination in volumetric Karl Fischer titration
Application bulletin: Coulometric water content determination according to Karl Fischer
Learn more about coulometric Karl Fischer titrators
Blog: Titer determination in Karl Fischer titration
Blog: Best practice for electrodes in Karl Fischer titration
What equipment is needed to perform Karl Fischer titrations?
To carry out volumetric titrations, you need a KF titrator with a completely equipped titration vessel, indicator electrode, dosing unit, and suitable reagents for volumetric KF titration.
For coulometric titrations, you need a coulometer, with a completely equipped titration cell, indicator electrode, a generator electrode with or without diaphragm, and a reagent suitable for coulometric KF titrations.
Do you want to learn more about KF titration?
The free monograph "Water determination by Karl Fischer titration" covers the theoretical aspects such as, reagents, chemical reactions, volumetry and coulometry, detection methods, and side reactions. It then presents water determination in different matrices, such as cosmetics, petrochemical products, plastics, and more.