Karl Fischer Titration Method for Moisture Analysis

Moisture content is one of the key parameters in many industrial and laboratory processes. When exceptional precision is required, especially for trace moisture (0.001% and less), Karl Fischer (KF) titration is indispensable.

What is Karl Fischer Method?

The Karl Fischer method is based on the chemical reaction between water and iodine in the presence of sulfur dioxide and alcohol. There are two main versions of the method:

• Volumetric KF titration – suitable for higher moisture contents (from 0.1% onwards)
• Coulometric KF titration – ideal for very low moisture contents (up to 10 µg H₂O)

Chemical Reaction

The chemical basis of the Karl Fischer method involves the following reaction:

Figure 1: Diagram of the Karl Fischer chemical reaction.

Sample Preparation and Challenges

Proper sample preparation is crucial for accurate moisture analysis. Different types of samples (solid, liquid, gas) require specific handling techniques to ensure reliable results. Common challenges include reactive substances and bound water.

Calibration and Maintenance

Regular calibration and maintenance of the Karl Fischer titrator and electrodes are essential for consistent performance. This includes replacing reagents, validating the method according to standards (e.g., ISO, USP), and ensuring the system is free from contamination.

Comparison with Other Methods

Karl Fischer titration is often compared with other moisture analysis methods such as halogen moisture analyzers and gravimetric methods (drying oven). Here is a comparative chart:

Figure 2: Comparative chart of moisture analysis methods.

Industrial Applications

In the plastics industry, precise moisture determination is crucial for preventing defects during molding and ensuring the mechanical properties of products. The Karl Fischer method provides reliable quality control in these processes.

Equipment for Karl Fischer Titration

Modern Karl Fischer analyzers are:

• Automated – with built-in pumps, drying units…
• Easy to use – with pre-set methods and connectivity to LIMS systems
• Reliable – with long-lasting electrodes and precise reagent dosing

Figure 3: Schematic of Karl Fischer titration apparatus.

Conclusion

If you are interested in how the Karl Fischer method can improve your moisture analysis, contact us. We are happy to advise you on the selection of suitable equipment and the establishment of the method.