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 7 days at 70 °C and 100% relative humidity |
Appearance of the substance
The substance, originally in the form of colourless crystals or a white, crystalline powder, remains unchanged after procedures A and B.
Gain of moisture
After procedures A and B: 4.5%
Chromatographic test
Adsorbent: Silica gel F-254
Solution applied to the plate: Substance dissolved in ethanol 95% - water (1:1).
Solvent system:
heptane: .........................................85 volumes
ethyl acetate: .................................10 volumes
acetic acid: ......................................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: The spot obtained from the solution of the sample subjected to procedure A and the spot obtained from the reference solution of acetylsalicylic acid display the same chromatographic characteristics of migration and detection. No secondary spots are revealed.
The spot obtained from the solution of the sample subjected to procedure B and the spot obtained from the reference solution of salicylic acid display the same chromatographic characteristics of migration and detection. There is no longer a spot corresponding to acetylsalicylic acid.
Colorimetric determination
To 10 ml of a 0.1% solution of the substance in water, add 1 ml of ethanol 95%, 5 ml of 1% ferric nitrate solution (9H2O) in 1% nitric acid, and dilute to 100 ml with water.
After procedure A: |
no violet coloration. |
After procedure B: |
very intense violet coloration. By comparison with a reference concentration series of salicylic acid, the degradation was assessed at 75%. |
Conclusion
No decomposition is detected by thin-layer chromatography after procedure A, but after procedure B, the substance is completely degraded.
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