Karl Fischer Titration Methods in pharma

Karl Fischer Titration Methods:

Karl Fischer titrations use volumetric or coulometric titrations to assess the amount of water in a sample by oxidizing sulfur dioxide with iodine in a buffer solution, and measuring the amount of water consumed in the reaction.

Invented by Karl Fischer, this technique has become commonplace. Various types of materials can be analyzed by the Karl Fisher Titration technique to determine their moisture content. An agent reacted with water content where the water content was changed into a non-conductive chemical. The Karl Fischer technique allows users to determine water’s content using either Karl Fischer coulometric titration or Karl Fischer volumetric titration.

There are two Karl Fischer Titration methods for the determination of water content present in the sample.

Karl Fischer Coulometric Titration:

In the coulometric Karl Fisher technique, moisture content can be calculated precisely. When the moisture content is less than 1 percent, this method is generally used. This method requires only one iodide-containing solution because the solvent and Karl Fischer reagent are mixed in the titration cell. Anodic oxidation of iodide from solution results in the production of iodine required for the KF reaction and the endpoint determines electrochemically.

By measuring the present current requirement for the electrochemical generation of iodine, the amount of iodine added to the sample can be calculated. The brown iodine solution is reduced to colorless iodide when it reacts with water. To complete the reaction, sulfur dioxide, iodide ions, base, and solvent (alcohol) are used.

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Karl Fischer titration methods: (Coulometric titration)

Karl Fischer Volumetric Titration:

The moisture content will depend on the volume or amount of reagent used to convert the water in this technique. Volumetric determination can be applied to determine water content greater than 1%. Several types of KF techniques use samples dissolved in a solvent prior to starting the titration. Until the water has been removed, a reagent is added, and the endpoint is determined potentiometrically.

A Karl Fischer reagent, which is used in this method, contains a buffer base, alcohol, sulfur dioxide, and a recognized amount of iodine, which is necessary to yield the titration endpoint.

By using these Karl Fischer titration methods water content can be determined.

 

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Karl Fischer Titration methods (Volumetric titration)

 

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Dr. Karl Fischer

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