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 a white or creamy white, crystalline powder, changes into a yellow paste, then into a yellow liquid after procedures A and B.
Gain of moisture
Before exposure to heat and humidity: |
8% |
After procedure A: |
30% |
After procedure B: |
45% |
Solubility
Sulfadimidine sodium is very soluble in water and soluble in methanol. After procedures A and B, the solubility is greatly decreased (formation of sulfadimidine).
Chromatographic test
Adsorbent: Silica gel F-254
Solution applied to the plate: Substance dissolved in water.
Solvent system:
n-butanol ................................ 50 volumes
ethane 95% ............................ 25 volumes
concentrated ammonia ............ 10 volumes
water ....................................... 25 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 sprayed with a 0.1% solution of 4-dimethylaminobenzaldehyde in ethane 95% containing 1% of concentrated hydrochloric acid.
Results: The spots obtained from the solutions of each of the samples subjected to procedures A and B, and the spot obtained from the reference solution of sulfadimidine sodium display the same chromatographic characteristics of migration and detection. No secondary spots are revealed.
Ultraviolet spectrophotometry
The absorbances measured at about 270 nm remain practically the same for the samples subjected to procedures A and B, as for the reference product and taking the gain of moisture into consideration.
Colorimetric determination
The method is based on a diazo-reaction with nitrite ion in acidic medium, the excess reagent being destroyed with sulfamic acid, and then coupled with N-naphthylethylenediamine. The absorbance is measured at about 535 nm.
The absorbances for the samples under test remain practically unchanged.
Conclusion
No decomposition is detected by TLC, by UV or colorimetric determination, but the gain of moisture and the change in solubility show that the substance is subject to decomposition under accelerated degradation conditions.
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