Titration is a typical laboratory technique in quantitative chemical analysis, which is primarily used to measure a known reactant’s unknown concentration. Nowadays, it is frequently done with a dedicated titrator.
The Karl Fischer titration is one of the various types of titration methods suitable for most purposes. This article walks you through all the essential details you need to know about the Karl Fischer titration.
Karl Fischer titration, an overview
Karl Fischer titration is a classic method of titration in the field of analytical chemistry first introduced back in 1935 by a German scientist called Karl Fischer. It was a titrimetric technique based on the Bunsen reaction utilised for sulphur dioxide determination in an aqueous solution.
Today, the Karl Fischer titration method is used to determine a sample’s trace amount of water. It can also be used to measure water content in solids, liquids, gases, pasty compounds, and oils.
What are the types of techniques in Karl Fischer titration?
Generally, there are two types of methods used in the Karl Fischer titration, namely, coulometric and volumetric methods, both of which are highly precise with a high water selectivity.
In volumetric Karl Fischer titration, the operator will add the titrant directly to the sample using a burette. The amount of moisture in the sample will be determined from the volume of titration. This method is appropriate to decide on the content of water down until 1%.
In the volumetric method, samples will be dissolved in Karl Fischer Solvent, which is typically methanol-based. Iodine will be added as part of a Karl Fischer Reagent comprises of sulphur dioxide and iodine dissolved in methanol and pyridine. The titrant will be measured potentiometrically.
On the other hand, coulometric Karl Fischer titration uses electrochemical. Unlike the volumetric technique, the coulometric method can determine a much lower level of water.
In this method, the Karl Fischer analysis only needs one solution containing iodine. Iodine needed for the Karl Fischer reaction is made from the solution’s iodide’s anodic oxidation. The titrant in the coulometric method is produced electrochemically in a titration cell.
In both of these methods, operators will transfer the sample to a titration vessel. They will then dissolve and titrate it. Specific samples are not soluble in any solvent and others may produce side reactions with the reagents of Karl Fischer. This situation allows operators to use the titrators with an oven.
Operators will heat the sample in an oven and water generated from the sample will be carried by a dry gas flow to the titration cell where it will react with the reagent. This method is an excellent solution for samples with poor solubility, samples that produce reaction when interacting with the solvent, and highly hydroscopic samples.
Application and reagents of Karl Fischer titration
Karl Fischer reagents are available in a wide range, depending on the user’s objectives and ecological awareness. Several auxiliaries exist, including fats’ and oils’ additives, reagents for low water content measurement, and solubilisers for substances with poor solubility.
Many industries apply Karl Ficher titration. In the food sector, for instance, the titration technique is used to determine the water content in flour, chips, noodles, fruit juices, and honey. On the other hand, in the petroleum sector, it helps determine the water content in all types of petroleum, gasoline, oils, and kerosene.
Karl Ficher titration is a classic titration technique with two distinct methods of titration, namely the coulometric and volumetric. It is widely utilised as a robust method for direct water content analysis in a variety of industries, including the food, petroleum, cosmetic, and pharmaceutical industries.