The Karl Fischer titration is used for quantitative determination of the water content. The method can be conducted volumetrically with one- and two-component reagents as well as coulometrically.
Both volumetric methods are based on the reaction of sulfur compounds with iodine in the presence of water. The reaction can only take place until all the water has been converted. Further injected iodine leads to a brown coloration, which serves as endpoint indication. The volumetric determination is particularly applicable for samples with a high water content. The coulometric method does not use a standard solution. The iodine required for the reaction is generated by anodic oxidation. Because of its sensitive dosing capability the method is used for samples with a low water content.
For samples with interfering components, the Karl Fischer titration with oven coupling can be applied. By the use of a carrier gas stream the released amount of water is transferred to the titration vessel and then quantified volumetrically or coulometrically according to Karl-Fischer. For temperature-sensitive samples, the required temperature can be reduced by adding a solvent (simultaneous extraction) so that the measurement result is not falsified by decomposition water or water of crystallization.