I have a Karl-Fischer reagent (for volumetric titration, which is a one-component reagent) with a titer of 5mg/ml. All references unanimously say the Karl-Fischer solution loses its capability when exposed to atmospheric moisture.
When the reagent is exposed to moisture, it absorbs H2O and the titer appears to increase. But I don't know the reason behind it. Can anyone explain in detail why this is happening?
The Karl Fischer reagent absorbs water from the air, which shifts the equilibrium of the reactions and increases the concentration of the active titrating components, leading to an increase in the observed titer. Proper storage and handling of the reagent is crucial to maintaining its accuracy and reliability for water determination.
Yes, Karl Fischer reagents are hygroscopic, meaning they readily absorb moisture from the atmosphere. This characteristic is crucial because moisture absorption can affect the accuracy and reliability of Karl Fischer titrations... When handling Karl Fischer reagents, be sure to close containers immediately after use to minimize exposure to atmospheric moisture. Use dry distribution techniques and work in a controlled environment with low humidity if possible... Pay attention to the expiration date of Karl Fischer reagents and follow manufacturer recommendations regarding shelf life and storage conditions. Discard reagents that have exceeded their recommended shelf life or have been compromised by exposure to moisture...Before performing titrations, standardize your Karl Fischer reagent against a known standard to confirm its potency. This helps ensure that the reagent is functioning correctly and that titration results are accurate.
Dear Mahsa Barati, the basic reaction is:
I2 + SO2 + H2O → 2HI + SO3
please have a look at the following link. My Regards
https://byjus.com/chemistry/karl-fischer-titration/#:~:text=The principle of Karl Fischer
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