The moisture content in drugs is one of the important indicators in the quality control process. The water in drugs can be divided into crystalline water and free water. The moisture content may directly affect the stability of certain drugs, and for water sensitive drugs, an increase in moisture content directly leads to a significant increase in impurities. For drugs containing crystal water, crystal water helps to form stable structures, such as trihydrate, and the degradation rate is significantly accelerated after losing crystal water
Karl Fischer Coulombic Moisture AnalyzerThe basic principle is that iodine oxidizes sulfur dioxide to sulfur trioxide, which requires the participation of water
1. Suitable for morphological samples, appropriate extraction solvents can be added to accelerate the release of water.
2. Generally, it is required to consume 10% to 90% of the titration solution in the burette volume of the Karl Fischer titration instrument for the added sample, and the measurement results are relatively accurate.
The optimal pH range for the Karl Fischer titration process is 5-7. If the addition of strong acid and strong alkaline compounds causes a significant change in the pH of the titrant, it can be improved by adding buffer salts.
If the sample reacts with iodine and other compounds in the Karl Fischer titration solution, water can be indirectly introduced into the titration solution by heating it in a drying oven, avoiding direct addition of the sample to the titration solution.