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 white powder, changes after procedure A into a pale yellow powder and into pale yellow compact blocks after procedure B.
Gain of moisture
Before exposure to heat and humidity: |
less than 3% |
After procedures A and B: |
not more than 3% |
Chromatographic test
Adsorbent: Silica gel 60 F-254
Solution applied to the plate: Substance dissolved in methanol.
Solvent system:
n-butanol: .........................50 volumes
water: ...............................20 volumes
ethanol: 95% ...................15 volumes
acetic acid: .......................15 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 of about 254 nm, and then left in a chromatographic chamber containing some iodine crystals until spots appear.
Results: The reference solution of benzathine benzylpenicillin shows numerous spots of different intensities. No additional spots are observed from the solutions of each of the samples subjected to procedures A and B, and the intensities remain the same.
Ultraviolet spectrophotometry
A reference solution in methanol shows three absorption maxima at 251 nm, 257 nm and 263 nm. A maximum appears with time at a wavelength of 312 nm.
The characteristics of the absorption spectra of the solutions of the substances subjected to procedures A and B are modified. An additional maximum at 293 nm appears that increases between procedures A and B.
Infrared spectrophotometry
No change is observed after procedures A and B.
Differential scanning calorimetry
No significant change is observed after procedures A and B.
Conclusion
Benzathine benzylpenicillin is subject to decomposition under accelerated degradation conditions as determined by ultraviolet.
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