Karl Fischer (KF) reagents can degrade due to side reactions that occur during storage. These reactions can cause the reagent to release water, which can affect the measured values. Some examples of side reactions include:
Oxidation of hydrogen sulphite
Oxidation of SO by aerial oxygen
Iodine-consuming side reactions without the participation of water
Here are some other things to consider when using KF reagents:
Titration cell
If the titration cell is not sealed properly, moisture from the air can enter and increase drift.
Septum
The septum through which samples are injected can wear out and need to be replaced.
Ground joints
The ground joints of the titration cell can leak, so they should be cleaned and lightly greased with high quality silicone grease.
Reagent change
When using a pump to change the reagent, moisture can get into the titration cell through the tubes. To avoid this, remove the tubing after changing the reagent and plug the opening with a stopper.
pH range
The optimal pH range for the Karl Fischer reaction is 5–8. If the sample is highly acidic or basic, it needs to be buffered to bring the
pH into this range.
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