What is Karl Fischer Titration?
Karl Fischer Titration is an accurate and widely accepted technique used to determine the moisture content in various substances. It is an electrochemical method that involves the titration of a sample with a Karl Fischer reagent, containing iodine, sulfur dioxide, and a base in a suitable solvent, such as methanol. The reaction between the reagent and water present in the sample consumes iodine, resulting in a change in the electrical conductivity of the solution.
Principle of Operation
The Karl Fischer reagent is standardized against water to determine its exact concentration. During titration, the reagent is added to the sample until the endpoint is reached, where all the water in the sample has reacted with the reagent. The endpoint is detected by monitoring the electrical conductivity of the solution using two platinum electrodes. As the water in the sample is consumed, the conductivity decreases, signaling the endpoint.
Method Variations
- Volumetric Titration: The Karl Fischer reagent is added volumetrically until the endpoint is reached, and the water content is calculated based on the volume of reagent consumed.
- Coulometric Titration: The Karl Fischer reagent is generated electrochemically within the titration cell. The current required to maintain the endpoint is measured, and the water content is calculated based on the amount of current passed through the solution.
Applications
Karl Fischer Titration is widely used in various industries to determine the moisture content in:
- Pharmaceuticals
- Foods and beverages
- Chemicals
- Petroleum products
- Environmental samples
Advantages
- High accuracy and precision
- Suitable for both liquid and solid samples
- Can determine water content in a wide range of concentrations
- Automated and relatively easy to perform
Disadvantages
- Not suitable for samples containing reactive substances that interfere with the reaction
- Can be affected by the presence of certain solvents
- Requires specialized equipment and reagents