Coulometric Karl Fischer titrators
Stand-alone or computer-controlled coulometers for the determination of low water content or moisture content (0.001 to 1%) by coulometric titration.
Coulometric Karl Fischer titrators are ideal to determine low moisture and water contents in liquid, solid, or gaseous samples (0.001 to 1% water content). Our range of coulometers covers any requirements and can be combined with the Karl Fischer oven method for the analysis of difficult samples.
- Accurate and reliable determination of trace-level water contents in the range of 0.001 to 1 %
- Various coulometer versions available, e.g., stand-alone or computer-controlled
- Difficult samples can easily be analyzed with the oven method
- Compliance with FDA Regulation 21 CFR Part 11 and EudraLex, Volume 4, Annex 11
Coulometers for every need
Metrohm offers various coulometric titrators to meet your requirements. Contact us to learn more about our coulometers.
| Coulometer | Features |
|---|---|
| OMNIS Coulometer |
Brochure: OMNIS Coulometer and OMNIS Sample Robot Oven (8.000.5475, PDF, 2.8 MB) |
| Titrando coulometers |
Brochure: 851 Titrando / 852 Titrando (8.851.5002, PDF, 889 KB) |
| Ti-Touch coulometer |
Brochure: 916 Ti-Touch, 915 KF Ti-Touch, 917 Coulometer (8.916.5004, PDF, 900 KB) |
| Eco Coulometer |
|
Sample preparation and automation for coulometric KF titration
For difficult samples, e.g., solid samples or samples that do not readily dissolve, you may apply the KF oven method. In this method, the sample is heated in an oven until the water is released, and the water vapor is transferred to the titration vessel for measurement.
We offer both manual ovens and automated sample changers with integrated ovens for increased sample throughput.
Coulometric Karl Fischer titrator – FAQs
What is coulometric Karl Fischer titration?
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)
Why is coulometric Karl Fischer titration used for water content determination?
Coulometric KF titration is a sensitive method suitable to determine low water contents between 0.001 and 1%. The coulometric method is an absolute method, meaning that there is no need for titer determination. In addition, a series of standards recommend coulometric Karl Fischer titration for water content determination:
| Standard | Name |
|---|---|
| ASTM D890 | Standard Test Method for Water in Liquid Pine Chemicals |
| ASTM D1123 | Standard Test Method for Water in Engine Coolant Concentrate by the KF Reagent Method |
| ASTM D1533 | Standard Test Method for Water in Insulating Liquids by Coulometric KF Titration |
| ASTM D3401 | Standard Test Methods for Water in Halogenated Organic Solvents and Their Mixtures |
| ASTM D4928 | Standard Test Method for Water in Crude Oils by Coulometric Karl Fischer Titration |
| ASTM D5460 | Standard Test Method for Rubber Compounding Materials - Water in Rubber Additives |
| ASTM D6304 | Standard Test Method for Determination of Water in Petroleum Products, Lubricating Oils, and Additives by Coulometric KF Titration |
| ASTM D7923 | Standard Test Method for Water in Ethanol and Hydrocarbon Blends by Karl Fischer Titration |
| ASTM E1064 | Standard Test Method for Water in Organic Liquids by Coulometric Karl Fischer Titratio |
| DIN EN ISO 12937 | Petroleum products - Determination of water - Coulometric KF titration method |
| ISO 10337 | Crude Petroleum - Determination of water - Coulometric KF titration method |
| UOP 481-10 | Water in Liquid Hydrocarbons, and Heavy Hydrocarbons by Vaporizer, using Coulometric Titration |
| USP | <921> Method 1c |
| EP | 2.5.32 Water: Micro Determination |
What is the difference between coulometric and volumetric titration?
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.
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.
What are the requirements for coulometric titration?
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.