Accelerated Degradation Experiment
Conditions
Procedure A1: |
10 days exposure at 50 °C and 100% relative humidity. |
Procedure A2: |
20 days exposure at 50 °C and 100% relative humidity. |
Procedure A3: |
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 a white, crystalline powder, changes after procedures A1, A2, A3 and B into a viscous, slightly chestnut coloured liquid. After cooling, solidification occurs and the substance appears as fine, white crystals.
Gain of moisture
Before exposure to heat and humidity: |
0.2% |
After procedures A3 and B: |
35% |
Chromatographic test
Adsorbent: Silica gel F-254
Solution applied to the plate: Substance dissolved in methanol.
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 examined under ultraviolet light at a wavelength of maximum output at about 254 nm, and then left in a chromatographic chamber containing some iodine crystals until spots appear.
Results: The spots obtained from the solutions of each of the samples subjected to procedures A1, A2, A3 and B, and the spot obtained from the reference solution of tetracaine hydrochloride display the same chromatographic characteristics of migration and detection. No secondary spots are revealed.
Ultraviolet spectrophotometry
The spectrum recorded between 200 nm and 350 nm, using 0.001% solutions of the samples subjected to procedures A3 and B in water, show an absorption maximum at about 311 nm. No degradation is observed.
Non-aqueous titration
The titrations with 0.1 N perchloric acid of 70 mg of each of the samples subjected to procedures A3 and B, dissolved in glacial acetic acid with the addition of mercuric acetate, show no degradation.
Colorimetric determination
To an aqueous solution of the samples subjected to the test, at pH 2, add picric acid, and extract the yellow picrate into chloroform. Absorbance of the organic layer measured at 410 nm: no degradation is observed.
Conclusion
No decomposition is detected by TLC, UV, the colorimetric determination and the non-aqueous titration, but the appearance of the substance changes after procedures A and B.
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