Accelerated Degradation Experiment

Conditions

Procedure A: 30 days exposure at 50 °C and 100% relative humidity.

Appearance of the substance

The substance, originally in the form of a white to cream-coloured powder, changes after procedure A into a dark brown liquid.

Gain of moisture

Chromatographic test

Adsorbent: Silica gel F-254

Solution applied to the plate: Substance dissolved in water.

Solvent system:

chloroform: .............................5 volumes
methanol: ................................4 volumes
concentrated ammonia: ...........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 left to dry in air and then examined under ultraviolet light at a wavelength of maximum output at about 254 nm. The plate is then sprayed with 0.25% of triketohydrindene hydrate in acetone and heated at 100 °C until spots appear.

Results: The spot obtained from the solution of the sample subjected to procedure A and the spot obtained from the, reference solution of gentamicin sulfate display the same chromatographic characteristics of migration, but the spot of the sample subjected to the test is less intense. Furthermore, an almost invisible secondary spot appears with the reference solution.

Ultraviolet spectrophotometry

The absorption spectrum is recorded using a 0.05% solution in water.

After procedure A an absorbance at 320 nm is observed, which is not present in the reference solution.

Conclusion

Gentamicin sulfate is subject to decomposition under accelerated degradation conditions.