Coulometric titration is used to determine trace-levels of water in samples within a range of 10 µg to 200 mg water. However, larger amount of water (> 10 mg) require a lot of time and/or may exceed the water capacity of the KF reagent, which could lead to incorrect results.

The coulometric method uses electric current to generate the iodine that is needed for the Karl Fischer reaction. Metrohm KF Coulometers apply variable current strengths and pulse lengths, which allows precise "iodine addition" even in the region of the endpoint.

Learn more about coulometric KF titration in the application bulletin:

Coulometric water content determination according to Karl Fischer (AB-137, PDF, 228 KB)

The main difference between coulometric and volumetric Karl Fischer titration concerns titrant addition. In volumetric Karl Fischer titration, the titrant is added directly to the sample with a buret. Coulometric Karl Fischer titration features a generator electrode, which electrochemically generates the required iodine for the titration directly in the titration cell. Learn more in our blog:

Karl Fischer titration: When to use volumetry or coulometry

Metrohm offers titrator solutions that perform volumetric or coulometric titration on separate titrators as well as both volumetric and coulometric titration in a single instrument. Contact us to learn more.

Requirements for coulometric titrations are the following:

• The process must take place with 100% current efficiency.
• No side reactions must occur.
• Oxidation or reduction must lead to a defined oxidation state.

Metrohm KF Coulometers meet these requirements with commercially available reagents.