Accelerated Degradation Experiment
Conditions
Procedure A: |
30 days exposure at 50 °C and 100% relative humidity. |
Procedure B: |
30 days exposure at 50 °C and 100% relative humidity followed by 5 days at 70 °C and 100% relative humidity. |
Appearance of the substance
The substance, originally in the form of a white or lightly-coloured, crystalline powder, changes after procedures A and B into a granular, dark chestnut coloured powder.
Gain of moisture
Before exposure to heat and humidity: |
25% |
After procedure A: |
39% |
After procedure B: |
63% |
Chromatographic test
Adsorbent: Silica gel G
Solution applied to the plate: Substance dissolved in 2 N acetic acid.
Solvent system:
methanol: .....................................100 volumes
concentrated ammonia: ................1.5 volumes
Development conditions: The solvent is allowed to migrate until the front reaches a line 15 cm from the starting line.
Detection: The plate is left in a chromatographic chamber containing some iodine crystals until spots appear.
Results: A spot appears on the starting line with the solution of the sample subjected to procedure A, and it is intensified with the solution of the sample subjected to procedure B. The main spot of the solutions of each of the samples subjected to procedures A and B decrease compared to the spot corresponding to calcium para-aminosalicylate.
Ultraviolet spectrophotometry
The absorbance is measured using 0.001% solutions in methanol.
| |
301 nm |
270 nm |
231 nm |
| |
|
|
|
Before exposure to heat and humidity |
0.537 |
0.706 |
0.640 |
After procedure A |
0.442 |
0.558 |
0.510 |
After procedure B |
0.376 |
0.493 |
0.448 |
Conclusion
Calcium para-aminosalicylate is subject to decomposition under accelerated degradation conditions.
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