Accelerated Degradation Experiment
Conditions
Procedure A: |
10 days exposure at 50 °C and 100% relative humidity. |
Procedure B: |
20 days exposure at 50 °C and 100% relative humidity. |
Appearance of the substance
The substance, originally in the form of bright yellow flakes, changes after procedure A into an orange-coloured paste, turning to orange-brown after procedure B.
Gain of moisture
Before exposure to heat and humidity: |
0.2% |
After procedure A: |
5% |
After procedure B: |
7% |
Chromatographic test
Adsorbent: Silica gel F-254
Solution applied to the plate: Substance dissolved in methanol.
Solvent system:
cyclohexane ............... 2 volumes
ether ........................... 2 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 reference solution of retinol shows a main spot at Rf 0.12, whereas the solution of the sample subjected to procedure A shows several secondary spots, and the main spot represents only about 10% of the original substance. After procedure B complete degradation is observed.
Ultraviolet spectrophotometry
The absorption spectrum shows that the maximum at 325 nm obtained with the reference substance disappears completely after procedures A and B.
Conclusion
Retinol is subject to decomposition under accelerated degradation conditions.
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