Karl Fischer titrators
Karl Fischer Titration
Water determination (also called moisture determination) is one of the most frequently performed analyses in laboratories around the world. This is not really surprising, as the water content directly influences the quality, processability, shelf life and stability of a wide range of products.
Karl Fischer titration has established itself as a reference method for general use. KF titration
- is highly specific and precise
- covers a wide concentration range: from ppm up to 100%.
- has short determination times.
There are two types of Karl Fischer titration: volumetry and coulometry
Volumetry
This is where higher (absolute) water contents are titrated. Volumetry also has the advantage that solid or pasty samples can be placed directly into the titration vessel and that work can be carried out with a wide range of organic solvents adapted to the sample.
Metrohm offers a large selection of instruments for volumetric KF titration – 901 Titrando and 870 KF Titrino plus - starting with simple instruments for routine water determination up to high-end instruments with many advantages.
Comparison of Metrohm's volumetric Karl Fischer titrators
Coulometry
In contrast to volumetric Karl Fischer titration, in KF coulometry no titrant is added, but the required iodine is generated directly in the iodide-containing electrolyte by electrochemical means («electronic buret»). For this reason coulometric water determination is primarily used for the determination of small amounts of water from 10 µg to 200 mg H2O with a resolution of 0.1 µg H2O.
Comparison of Metrohm's coulometric Karl Fischer titrators
Sample Preparation
Often sample preparation with the KF Oven can be recommended. In this case the sample is heated in the upstream oven, the released water is transported in a dry stream of carrier gas to the KF titration cell where it is determined. As only water enters the titration cell and the sample itself does not come into contact with the KF reagent, side-reactions and matrix effects are avoided.
The 874 Oven Sample Processor allows the heating method to be automated.
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