Karl Fischer

1. Why do we detect water content in dosage units?

· Because the presence of water content is quite harmful; a higher amount of water can cause microbial growth and generate impurities.

2. Why do we use Karl Fischer for the determination of water content instead of a Moisture Balance?

· A Moisture Balance gives the result of water content along with volatile impurities, whereas Karl Fischer detects absolute water content.

3. What is Karl Fischer?

•  Karl Fischer is an autotitrator. 

4. When and by whom was Karl Fischer discovered?

•  Karl Fischer was discovered by a German chemist named Karl Fischer in 1935.

5. In which chapter of the US Pharmacopeia is the water determination technique discussed?

•  In chapter 921.

6. What are the Karl Fischer reagents? Write their names.

•  Sulfur dioxide

•  Iodine

•  Alcohol (Methanol – CH3OH)

•  Pyridine C5H5N or Imidazole. 

Pyridine is carcinogenic, which is why lab management replaces it with imidazole.

7. Why do we place Karl Fischer reagent in dark amber glass?

•  Karl Fischer reagent is photosensitive, which is why we use dark amber glass for storage.

8. What is the principle of Karl Fischer?

9. What is drift in Karl Fischer?

•  Drift is the process to detect and zero atmospheric moisture.

10.What do we use to calibrate Karl Fischer?

· Disodium Tartrate, with a water content of 15.6%

· Water (H2O), with a water content of approximately 99.99%.

11. Why do we use Disodium Tartrate for the calibration of Karl Fischer? 

· Disodium Tartrate (DST) is used as a primary standard in Karl Fischer Titration because it easily reacts with Karl Fischer reagents and has a highly stable crystalline structure. 

12. What is a primary standard in titration? 

· A primary standard is a key tool in titrations, providing a benchmark for determining the concentration of an unknown solution. Its high purity and stability ensure the accuracy and reliability of the titration results.