Question

Dear sir
i want to determine water (100 ppm)in condensate sample by karlfisher coulometry method but our sample have H2S concentration 600 ppmwt can interfere with karlfischer solution in ASTM E203 CORRECTION IS ONLY FOR MERCAPTAN can you guide me how can i?
best regards
EDWARD

Answer 1

Answer on Question #41111 – Chemistry – Other

Question:

want to determine water (100 ppm) in condensate sample by karlfisher coulometry method but our sample have H2S concentration 600 ppmwt can interfere with karlfischer solution in ASTM E203 CORRECTION IS ONLY FOR MERCAPTAN can you guide me how can i?

Answer:

Actually, H₂S doesn't interfere so much while detecting water by Karl Fisher method. But if there are small amounts of water and great concentration of H₂S (as in your case), it can cause top-heavy result.

You can oxidize H₂S previously by adding an accurate amount of I₂. The following reaction will take place

I₂ + H₂S = S + 2HI

Then the precipitate S can be removed by filtration.