Karl Fischer was a German chemist who discovered that the Bunsen Reaction between iodine and sulfur dioxide could be modified to help determine water content in a non-aqueous system. In 1935, he published this new method, which came to be known as Karl Fischer titration.
To learn more, let’s take a look at a few interesting facts about this very important titration method!
1. It Has Several Applications Crossing Many Industries
As a student of pharmaceutical quality assurance, you will soon learn about the Karl Fischer Titration method. This method is one of the most accurate procedures for determining the water content in liquids, gases, and solids. Trusted for its robust methodology and precise results, it’s a key procedure crossing many business niches, including such industries as:
- Food
- Cosmetic
- Petroleum
- Pharmaceutical
Determining the water content of a product is crucial for ensuring quality, efficacy, and shelf life. This is because too much or too little of it can make a difference to these and other factors.
2. It Works By Reading an Excess of Iodine
The Karl Fischer reaction is based on the oxidation of sulfur dioxide by iodine with the consumption of water in a buffered solution. In this reaction, water and iodine are used up in an equimolar ratio. When all the water has been consumed, the reaction reaches its end. From there, the water content is calculated and determined according to the amount of reagent added.
Samples must be prepared differently depending on if they are in solid, liquid, or gas form
3. It’s Become an Automated Procedure
During Karl Fischer’s experimentation phase with the procedure, the chemist fine-tuned the method using the alcohol of methanol as the solvent, with a pyridine base as the buffering agent. Today, ethanol, methanol, or a propylene-glycol mixture can be used. Originally performed manually, this method has now been automated for efficient application by:
- major chemical manufacturers
- petroleum refiners
- other industry labs
- governments worldwide
- academic research organizations
4. There Are Two Main Types of the Method
Students of pharmaceutical quality control should know of the two principal forms of Karl Fischer titration used across industries. These are:
- Volumetric titration
- Coulometric titration
Both of these methods are very rapid and highly precise for determining water in free and contained forms. Volumetry is most ideal for determining water content in the range of 100 ppm to 100%, with coulometry able to determine much lower levels of water, in ranges between 1 ppm to 5%.
Coulometric titration can determine very low levels of water
Why the Method Matters to Students of Pharmaceutical Quality Control
People working in pharmaceutical quality assurance come to know that the water content of active pharmaceutical ingredients and excipients can directly impact the efficacy, stability, potency, and expiration expectancy of a final product. For this reason, precise water content measurement is critical as part of the quality control and quality assurance of all kinds of pharmaceutical products.
Water content is measured in all kinds of pharma products, as it can impact potency and stability
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