Accelerated Degradation Experiment
Conditions
Procedure A1: |
10 days exposure at 50 °C and 100% relative humidity. |
Procedure A2: |
20 days exposure at 50 °C and 100% relative humidity. |
Appearance of the substance
The substance, originally in the form of a white or yellowish white, crystalline powder, changes after procedure A1 into a colourless liquid that recrystallizes at room temperature, and after procedure A2 recrystallization does not reoccur, not even at a temperature of 0 °C.
Gain of moisture
Before exposure to heat and humidity: |
about 0.2% |
After procedure A1: |
46% |
After procedure A2: |
67.5% |
Chromatographic test
Adsorbent: Silica gel F-254
Solution applied to the plate: Substance dissolved in water.
Solvent system:
chloroform .............. 6 volumes
acetone .................... 4 volumes
Development conditions; The solvent is allowed to migrate until the front reaches a line 15 cm from the starting line.
Detection: Prepare the following spraying solutions:
Solution I - 0.05 N silver nitrate in methanol.
Solution II - 30% aqueous solution of formaldehyde.
Solution III - 2 N potassium hydroxide in methanol.
Solution IV - A mixture of equal volumes of 40% nitric acid with an aqueous 3% hydrogen peroxide solution.
After drying the plate, spray it in the following manner: Spray with solution I, allow to rest at room temperature for 30 minutes; spray with solution II, allow to rest at room temperature for 30 minutes; spray with solution III, heat at 100 °C for 30 minutes; spray with solution IV, allow to rest in the dark overnight, then expose it to daylight for a few hours. Violet spots of the chlorine derivatives appear on a white background.
Results: The spots obtained from the solution of the sample subjected to procedure A1 is weaker by a factor of 2 with an important spot on the starting line when compared with the reference solution of metrifonate. The main spot is intensified after procedure A2.
Determination of ionisable chlorine by argentometry
Before exposure to heat and humidity: None. |
After procedure A1: |
2.8% calculated with reference to the dried substance. |
After procedure A2: |
5.1% calculated with reference to the dried substance. |
Determination of free aldehydes
Absorbance of a reference solution of metrifonate containing 100 µg/ml: 0.075
Absorbance of a solution of the substance subjected to procedure A1 containing 100 µg/ml: 0.62
Absorbance of a solution of the substance subjected to procedure A2 containing 10 µg/ml: 0.22
Conclusion
Metrifonate is subject to decomposition under accelerated degradation conditions.
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