Karl Fischer titration is based on a chemical reaction that depends on the presence of water. There are several types of methods used in chemistry for determining moisture content, including Karl Fisher titration, loss on drying, and spectroscopy, but Karl Fischer titration has a major advantage that provides high precision and accuracy.
Karl Fisher titration is a titration method that determines the amount of water (moisture) present in a given sample by using two different techniques such as volumetric or coulometric titration. Determination of water content is necessary for many applications for quality control, including chemicals, pharmaceuticals, and foods. Karl Fisher (KF) titration is a widely used method of quality control to meet the needs of various industries and research work.The oxidation reaction between iodine and sulfur dioxide is the fundamental principle of Karl Fischer.
The Karl Fisher reagent contains iodine, sulfur dioxide, a base, and a solvent, such as alcohol and dry methanol is also used in the process of KF.
Advantages of Karl Fischer Titration:
- The major advantage of Karl Fischer titration is that it is used for volatile substances as well as non-volatile substances that are not possible in the loss-on-drying.
- It is suitable for liquids, solids as well as gaseous samples.
- It gives higher accuracy and precision than other techniques.
- A small amount of sample is required to perform the test of Karl fisher.
- Karl Fischer titration is easy to perform and its analysis period is short.
- It has an unlimited measurement range from 1ppm to 100% of the sample.
- The preparation of the sample in Karl Fischer titration is simple.
- It is suitable for automation; nowadays different types of automated devices are available.
- It does not contain heat so there is no possibility of degradation, reaction, and loss of sample.
- A spectrophotometric detector may be permitted for visual identification of the endpoint.
Disadvantages of Karl Fischer Titration:
- The major disadvantage of Karl Fischer is that the KF reagents have water equivalents that change over time, and they must therefore be regularly calibrated when the use of the volumetric method.
- It is an expensive analysis, requiring certified water standards and fresh Karl Fisher reagent to perform calibration and titration.
- The manual volumetric titration consumes more solvent.
- Karl Fischer titration is a destructive technique.
- Strong acids, boric acids, aldehydes, ketones and, metal peroxides are not suitable for KF titration, because their reaction with methanol solvent produces water.
- KF titration relies on a redox reaction, so any compound that is an active redox chemical in the reagent reacts with iodine and produces incorrect results.
- The sample range of the Karl Fisher analysis is short because many compounds undergo side reactions and are not suitable for KF titration.
- Coulometric titration takes longer and is suitable for samples that contain small amounts of water.
Advantages of Coulometric Titration:
Advantages major advantage of coulometric titration is that the electrochemical generation of a titrant is extremely sensitive and controllable compared to mechanical addition of a titrant using a burette.
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