The volumetric or coulometric titration are the types of Karl Fischer titration they both are used to quantify the amount of water present in a given analyte, however, they also have some differences, let’s check them.
The Karl Fischer titration is a quantitative chemical analysis used to determine the concentration of water content in the sample. The Karl Fischer titration is based on the principle of the oxidation reaction between iodine and sulphur dioxide. Water reacts with sulfur dioxide and iodine to form hydrogen iodide and sulfur trioxide. When all of the water has been consumed, an endpoint has been reached. It can be carried out using volumetric or coulometric measurement methods.
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What is Coulometric Karl Fischer Titration?
It is a type of titration in which the reagent and solvent are combined in the titration cell. The induction of electric current releases the reagent when a sample is placed in a titration cell and dissolved. The amount of current needed to convert the water determines how much moisture is present. This process is typically applied when the moisture content of a sample is less than 1% or the moisture content is less than 200 micrograms. A coulometric Karl Fischer titrator is also known as a coulometer.
What is Volumetric Karl Fischer Titration?
It is a type of titration in which water content is estimated by measuring the volume of Karl Fischer titrant which contains alcohol, sulfur dioxide, a buffer base, and a known concentration of iodine. It is necessary to reach the endpoint in volumetric Karl Fischer titration. Before starting the titration process, the samples are dissolved in a solvent, and then a reagent is added until all the water in the sample is consumed. The resulting excess of iodine can be determined potentiometrically and it is ideal for the sample that contains higher levels of moisture (up to 100%).
Difference between coulometric and volumetric titration:
- The major difference between coulometric and volumetric titration is that in the volumetric method a titrant is directly added to the sample using a burette, whereas in the coulometric method a titrant is electrochemically produced inside the titration cell.
- The coulometric method is used to determine the concentration of liquid and gaseous samples, while the volumetric method is used to determine the concentration of solid, liquid, and gaseous samples.
- The coulometric titration has poor system flexibility, while volumetric titration has good system flexibility.
- Coulometric KF titration can measure moisture content at levels less than 1% or less than 200 µg, while volumetric KF titration can measure moisture content from 0.1 % to 100%.
- The coulometric titration has limited co-solvents, while volumetric titration has a modified solvent system.
- In coulometric Karl Fischer titration, there is no option of temperature modification, while in volumetric Karl Fischer titration the modification of temperature can possible.
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