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In 1935, a German scientist named Karl Fischer made a discovery that provided a new perspective for scientific computing at the time. He found that the sulfur dioxide added to the reaction would determine the water content in the titration. This discovery is today known as the Karl Fischer titration method.

What is Karl Fischer titration?

Karl Fischer titration is a scientific method used to determine the moisture content in various samples. This concept refers to the titration method involving sulfur dioxide, iodine, and aqueous solutions in the endogenous reaction.

In its calculation, Karl Fischer titration involves three main components, namely an analytical balance with a minimum resolution of 0.1 mg, a long syringe with a small needle, and Karl Fischer reagent for determining water content.

All components in the instrument must always be placed in an area with constant room temperature and humidity levels. In this way, external factors such as temperature and humidity will not affect the accuracy of moisture calculation.

Karl Fischer titration principle

The oxidation of sulfur dioxide by iodine is the main principle of Karl Fischer titration. In a buffer solution, the combination of two solutions can determine the water consumption in the solution, which helps to calculate the water content of the final product. In other words, when iodine and water titrants reach equilibrium, Karl Fischer titration will reach its final stage.

If there is an excess of iodine, the dual platinum electrode used as an indicator will change color. When this situation occurs, titration must be stopped immediately. Then the water content can be determined by the amount of reagent added to the solution.

Karl Fischer coulometric titration 

Basically, Karl Fischer titration can be divided into two methods, namely volumetric titration and Coulombic titration. However, with the development of applications, these two methods can also be combined into combined or mixed methods.

The following is a brief explanation of the three methods used in the Karl Fischer titration process.

1. Volume method

The volumetric method is a good way to calculate the minimum moisture content, such as within the range of 0.005-0.01% (50-110 ppm). This method involves adding Karl Fischer reagent composed of methanol solution and a mixture of sulfur dioxide, iodine, and pyridine. Use an electric burette to titrate the solution into the sample. The water content can be determined by adding the volume of the solution.

2. Coulomb method

The next method for Karl Fischer titration is the Coulombic method. This calculation is performed during the electrochemical process and only involves one iodine solution. The amount of iodine solution added will be calculated during the electrochemical process. When a solution reacts with water, it is reduced, resulting in a colorless endpoint.

3. Mixed method

The third method is called the mixed method, which is a combination of the first two methods, namely the volume method and the electric quantity method. As the name suggests, this method combines the two working principles mentioned above. Calculate the iodine solution generated during the electrochemical process until the water content exceeds the predetermined level. Once known, other solutions will be added simultaneously.

This is the information you need to know about the meaning, principles, and Karl Fischer titration method. In order to make the procedure for determining the moisture content of the sample easier and more accurate, you need to choose the most suitable equipment.

The Karl Fischer titrator in Toledo is one of the main solutions. This excellent equipment provides true functionality for testing the moisture content in turbine oil, hydraulic control oil, and various other samples.