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 yellow, crystalline powder, darkens in colour after procedure A, and after procedure B changes into a brown-black powder.
Gain of moisture
Before exposure to heat and humidity: |
2.5% |
After procedures A and B: |
8% |
Chromatographic test
Adsorbent: Cellulose without fluorescent indicator, impregnated with 0.1 M disodium edetate and dried at 100 °C for 30 minutes.
Solution applied to the plate: Substance dissolved in methanol. After application the plate is exposed to ammonia vapours for 15 minutes.
Solvent system:
n-butanol: .................................10 volumes
pyridine: .....................................6 volumes
ethyl acetate: ..............................6 volumes
water: .........................................7 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 exposed to ammonia vapours, and then examined under ultraviolet light at a wavelength of maximum output at about 365 nm.
Results: The spot obtained from the solution of the sample subjected to procedure A and the spot obtained from the reference solution of doxycycline hydrochloride display the same chromatographic characteristics of migration and detection. After procedure B intense secondary spots appear.
Ultraviolet spectrophotometry
The absorption spectrum is recorded between 200 nm and 400 nm using a 0.002% solution of each of the samples subjected to procedures A and B in methanolic 0.1 N hydrochloric acid; a maximum is observed at about 349 nm.
After procedures A and B, no change is observed in the shape of the spectra. |
After procedure A: |
no change |
After procedure B: |
30% degraded. |
Colorimetric determination
The content of doxycycline hydrochloride is determined with molybdotungstophosphate reagent in a medium containing carbonates, and the absorbance is measured at 750 nm.
After procedure A: |
no degradation |
After procedure B: |
30% degraded |
Conclusion
Doxycycline hydrochloride is subject to decomposition under accelerated degradation conditions.
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