Karl Fischer Titrator (Coulometric)
Measures very small amounts of water by generating iodine electrically inside the cell and counting the charge needed to react with all the water. Suited to trace water, from ppm levels up to about 1–5%.
- Pharmaceutical
- Biotech
- Chemicals
- Petrochemicals
- Electronics / batteries
Test your KF titrator (coulometric) knowledge
Multiple-choice questions
Pick an answer to see whether you are right and why.
Q1. In coulometric KF, where does the iodine come from?
basicQ2. Why does a coulometric KF titrator not need a titre determination?
basicQ3. Approximately how much charge is needed to generate the iodine for 1 mg of water?
intermediateQ4. Which sample is best suited to coulometric rather than volumetric KF?
basicQ5. Three injections of a 1.0 mg/g water standard give recoveries of 99.2%, 99.5% and 99.7%. What does this show?
intermediateQ6. Drift is 4 µg/min and a determination lasts 3 minutes. How much is subtracted from the result?
intermediateQ7. A lyophilised product does not dissolve in the anolyte. What is the usual solution?
advanced
Viva questions
Think of your answer first, then open it to compare.
1. Explain the difference between volumetric and coulometric KF.
Both use the same reaction of water with iodine. Volumetric KF adds iodine in a titrant from a burette and needs the titre determined; it suits about 0.1–100% water. Coulometric KF generates iodine electrically, measures the charge and needs no titre; it suits trace water from ppm levels to a few percent.
2. Why is a low, stable drift even more important in coulometric KF?
Samples contain only micrograms of water, so a few micrograms per minute of leaked moisture is a large share of the result. A stable drift can be corrected; a high or changing drift makes the correction unreliable.
3. How do you inject a liquid sample correctly and determine its mass?
Rinse the syringe with sample, fill it, wipe the needle and weigh. Inject through the septum below the liquid surface without touching electrodes, then reweigh the syringe. The difference is the injected mass, entered into the instrument.
Keep every KF titrator (coulometric) in control: usage logs, calibration and maintenance schedules, and automatic blocking of overdue instruments.