Chuẩn độ Karl Fischer

Karl Fischer (KF) titrators are used 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 titrators can be used for moisture determination (i.e., water content determination) in all sample types: liquids, solids, slurries, and gases​
• KF titrators are applied over a wide concentration range from ppm up to 100%​
• KF titrators are fast and highly selective​
• KF titrators supply reproducible and correct results​

A Karl Fischer (KF) titrator determines water content in samples using a specific chemical reaction. The process is based on two redox reactions involving classical alcohol-based Karl Fischer reagents. Methanol and sulfur dioxide form an alkyl sulfurous acid, which, in the presence of water and iodine, is oxidized in a water-consuming reaction. The reaction stops when all the water is consumed, and a small excess of iodine signals the endpoint of the titration

Manual or fully automated Karl Fischer instruments are available. 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​

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When selecting a KF titrator, consider:

• Water content range: Use coulometry for trace levels (ppm) and volumetry for higher concentrations.

• Sample type: Liquids, solids, or gases may require different accessories (e.g., oven method for solids).

• Throughput: For high sample volumes, automation (e.g., OMNIS Sample Robot) boosts efficiency.

• Compliance needs: Ensure the system supports GMP/GLP, 21 CFR Part 11, and pharmacopeia standards.

• Modularity: Metrohm’s OMNIS platform grows with your lab – start small and expand as needed.

Our Karl Fischer experts are happy to assist you with your questions:

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Metrohm is present in over 80 countries to ensure local training and support.

Metrohm offers:

• On-site installation and training

• Application support from our global network of experts

• Webinars, tutorials, and documentation

• Service contracts for preventive maintenance and calibration

Learn more in our blog article:

Blog: Karl Fischer titration – When to use volumetry or coulometry

Low levels of water in the range of 0.001% up to 1% are analyzed best with a Coulometer.

Depending on the water content, you need to select the appropriate generator electrode. The generator electrode without diaphragm combines easy handling with reliable results. For the determination of trace level water contents, we recommend using the generator electrode with diaphragm.​

Metrohm offers various Coulometers, from basic stand-alone versions to high-end computer-controlled coulometric systems with automation and sample preparation options:

Go to coulometric Karl Fischer titrators

Trace levels of water in solvents and oils are analyzed best with a Coulometer.

Depending on the water content and which KF reagent you use, you have to select the appropriate generator electrode. With the generator electrode without diaphragm, only one reagent is required. The generator electrode with diaphragm is recommended for the determination of very low water contents and when using KF reagents containing solubilizers (e.g., chloroform).​

Metrohm offers various Coulometers:

Go to coulometric Karl Fischer titrators

There is no general answer to this question. The optimal KF method depends on the water content of the sample and not on the sample size.

Read our blog article to learn more about this topic:

Blog: Karl Fischer titration – When to use volumetry or coulometry

Low levels of water are analyzed best with a Coulometer. The coulometric method is very sensitive. Therefore, we do not recommend opening the titration cell to add a solid sample. Atmospheric moisture would falsify the results.

The oven method is the optimal solution for solids with low water content. Learn more about the oven method in our blog and application bulletin:

Blog: Oven method for sample preparation in Karl Fischer titration

Application Bulletin: Automatic Karl Fischer water content determination with the 874 Oven Sample Processor

Watch the following video to see the OMNIS Coulometer and OMNIS Sample Robot Oven in action.

Yes, potentiometric and Karl Fischer (volumetric and coulometric) titrations can both be run on an OMNIS titrator. OMNIS titrators offer unparalleled modularity and allow adding functionality at any time. Additional titration modes can be combined and added whenever needed.

This modularity is unique to Metrohm's OMNIS platform, allowing laboratories to adjust quickly. Learn more about the modularity of OMNIS:

See OMNIS titrators

Yes, the OMNIS Coulometer allows coulometric bromine index determinations according to ASTM D1492-08.

See OMNIS Coulometer