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Wednesday, September 5, 2018

Karl Fischer Titration Methods

The reaction of Karl Fischer titration uses volumetric or coulometric titration to determine the amount of water present in a sample based on the oxidation of sulfur dioxide by iodine, in which water is consumed in a buffer solution.

This technique was discovered by Karl Fischer. Karl Fisher Titration is a method to determine the content of moisture in different types of substances. It depends to a reagent that reacts with water content and changes water content into the non-conductive chemical. Volumetric KF titration and Coulometric KF titration are two techniques available for determination of water by the Karl Fischer: 
Volumetric Karl Fischer Titration:
With this technique, the moisture content determines on the base of volume or amount of reagent used to convert the water. The volumetric determination is appropriate for water content determination of down to 1% of the water. In these types of KF technique, samples are dissolved in a solvent before the starting the titration, until the water has removed a reagent is added and the endpoint is determined potentiometrically.
In this method, the Karl Fischer reagent contains a buffer base, alcohol, sulfur dioxide, and a recognized amount of iodine, which is necessary to achieve the titration endpoint. 
Coulometric Karl Fischer Titration:
The benefit of the coulometric Karl Fisher technique is the capability to precisely calculate the quantity of moisture content. Generally, this method is used if the moisture content is less than the 1 %. In this method, the solvents and reagent mixed in the titration cell and have need of just one iodide-containing solution. Iodine required for the KF reaction produced by the anodic oxidation of the iodide from solution and the endpoint is determined by electrochemically.
The quantity of iodine added in the sample is calculated by measuring the present current requirement for the electrochemical generation of iodine. When reacting with water, the brown iodine solution is reduced to the colorless iodide. In this method, sulfur dioxide, iodide ions, base, and solvent (alcohol) are used to complete the reaction.


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