Karl Fisher Titration for Water Determination in Methanol

In the Volumetric Karl Fischer Titration, a solution with an exactly known concentration of iodine is added to sample by means of an electric burette. The amount of iodine added to the sample is calculated from the volume of iodine solution used.

Reaction:

SO₂ + CH₃OH + B ↔ CH₃SO^3-+ HB⁺ 

CH₃SO^3-+ H₂O + I₂ + 2B → CH₃SO₄^-+ 2HB⁺+ 2I^-

Cathode: I₂ + 2e^- → 2I^-

Anode: 2I^-- 2e^- → I₂

Both aldehydes and ketones pose problems with Karl Fischer titration because they form acetals and ketals respectively with conventional KF reagents.

This application is used to determine the water content in organic raw materials and solvents by volumetric Karl Fischer titration, excluding aldehydes and ketones.