Top 25 Karl Fischer titration interview questions and answer in pharma

Here in this article, we will try to understand the Karl Fischer titration interview questions and answer for quality control in pharmaceutical.

Karl Fischer is a widely used technique for the determination of water in the pharmaceutical industry. Karl Fischer is used to determining the only water content present in the sample but not other volatile impurities in the samples.

Generally, while interviews of Quality control of pharmaceutical, karl fischer titration interview questions are common, so today in this article we will see what are those related KF interview questions.

Karl Fischer titration test is used to performing Karl Fischer moisture analysis. In this test, we can measure the moisture content present in the sample.

Karl Fischer titration interview Questions and answer

Question 1: What is Karl Fischer (KF) general chapter number as per USP?

Answer: USP general chapter Number <921>, Water Determination.

Question 2: What is volumetric karl fisher titration principle?

Answer: It is a titrimetric determination of water is based on a qualitative reaction of water with anhydrous sulphur dioxide and iodine in the presence of a suitable base.

Question 3: How many methods of determination of water?

Answer: There are two methods of determination of water.

Question 4: What are the two methods of water determination?

Answer: 1. Volumetric water determination 2. Coulometric water determination

Question 5: What is the difference between Volumetric Karl Fischer water determination and coulometric water determination?

Answer: In volumetric determination, the titrant is added directly through the burette while in coulometric determination titrant generated electrochemically in the titration vessel.

Question 6: When we use volumetric karl fischer titration?

Answer: We use volumetric Karl Fischer titration for higher concentration solutions. We use the volumetric Karl Fischer titration method when the water concentration is 100ppm to 100% and during titration iodine is added using a burette.

Question 7: Why we use volumetric Karl fischer titration for water determination?

Answer: 1. It consumes less quantity.

2. It has high sensitivity

3. High speed for determination

4. No need to replace the solvent each time.

5. Without changing reagent multiple samples can be tested.

Question 8: What is karl fischer titration reaction?

Answer: Chemical reaction for the karl fischer titration is;

ROH + SO2 + 3 RN + I2 + H2O —-> (RNH)SO4R + 2 (RNH)I

Question 9: How to prepare karl fischer reagent? Or What is kf reagent?

Answer: Add 125 gm of iodine to a solution containing 670ml of methanol and 170ml of pyridine. place 100ml of pyridine in 250ml of graduated cylinder and keep the pyridine cold in an ice bath, pass in the dry sulfur dioxide until volume reaches to 200ml. Slowly add this solution, with shaking to the cool iodine mixture. Allow the solution to stand overnight.

Or

Commertially available karl fischer reagent pyridine free can be used.

Question 10: How to perform karl fischer moisture analysis?

Answer: Clean the previous traces of sample solution from the titration vessel. Rinse it with a suitable base. Fill the required quantity of suitable base into the vessel. Start the instrument and wait till the drift is ready, once the drift is ready then weigh and add your sample quantity into the titration vessel without touching the vessel wall.

If the sample is in liquid form, weigh the sample in the syringe and add it through the injection port without touching the vessel wall.

Question 11: What is pyridine free karl fischer reagent?

Answer: Pyridine free karl fischer reagent means pyridine is replaced by imidazole for routine usage.

Question 12: What is Drift in Karl Fischer titration?

Answer: Drift is a background moisture that detecting by karl fischer titrator.

Question 13: What are the content of KF Reagent?

Answer: Sulphur dioxide, Iodine, Imidazole/Pyridine, and suitable base (Methanol/Ethanol)

Question 14: Why pyridine not used in KF titration?

Answer: Pyridine is carcinogenic and it is affects of reproductive system of human.

Question 15: Which standard is used for karl fischer standardization?

Answer: Disodium tartrate dihydrate (DST) is used for standardization of Karl fischer.

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Question 16: Why DST is used for kf standardization?

Answer: It is primary standard, it is stable as well as non-hygroscopic and it has stoichiometric water content 15.66%

Question 17: What are the parts of karl fischer instrument?

Answer: Detection electrode, Anode chamber, rotor, electrode, drying tube, Drain pipe, KF reagent, cathode chamber, sample injection port, Magnetic stirrer.

Question 18: What is difference between water content by KF and LOD?

Answer: Water by KF is measure only moisture content present in the sample but LOD measures moisture content, as well as volatile impurities, presents in the sample.

Question 19: What are the KF titrator brands are available in the market?

Answer: Metrohm 831 karl fischer, Mettler Toledo kf titrator.

Question 20: What are the factors affecting on Karl fischer titration?

Answer: 1. pH of the sample

2. Environmental humidity

3. Side reaction between of the sample and KF reagent

4. Medium of the work

Question 21: Which type of karl fischer titration is?

Answer: It is Redox type of titration.

Question 22: Which electrode is used in KF titration?

Answer: Platinum electrode is used in KF titration.

Question 23: How does karl fischer titration works?

Answer: There are two method of karl fischer titration; Coulometric karl fischer titration and volumetric karl fischer titration;

In a coulometric titration, the reagents and solvents are combined in the titration vessel, the sample is dissolved into the titration cell, releasing the reagent by the induction of an electrical current. The amount of current is needed to release enough reagent to convert the water into the non-conductive chemical determines the amount of moisture in the sample. Here endpoint detected electrochemically.

In a volumetric titration, moisture determination is based on the amount of reagent used to convert the water into a non-conductive chemical. Here endpoint detected potentiometrically.

Till the time we have read Karl fischer titration interview questions now, we will see the coulometric interview questions.

Question 24: When we use coulometric Karl Fischer titration?

Answer: Coulometric Karl Fischer titration method is used to detect the low concentration solutions. Coulometric karl fischer titration method is used, when water concentration is 1 ppm to 5% and iodine is generated electrochemically.

Question 25: Why we use karl fischer coulometric titration for water determination?

Answer: 1. This method is highest precise

2. Low concentration water content can be detected.

3. Low cost reagent

4. More stable titre

5. More convenient for atomization.

Conclusion:

I hope you all enjoy the Karl Fischer titration interview questions and answers and can prepare yourself for the interview at least for quality control in pharmaceutical. If you have any questions related to Karl Fischer titration you can suggest me.

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