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Hydrolysis

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Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
PHYSICO-CHEMICAL PROPERTIES
- Vapour pressure: 0.077 mm Hg
- Water solubility: Cannot be determined due to limited stability of test substance in aqueous solutions (half life time < 4 minutes)
- Stability of test material at room temperature: Stable

OTHER PROPERTIES (if relevant for this endpoint) Quick hydrolysis of test substance expected
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
- Sampling methods for the volatile compounds, if any: None
- Sampling intervals/times for pH measurements: Four minutes and one hour after preparation a sample was taken from the upper organic phase and analysed.
- Other observation, if any (e.g.: precipitation, color change etc.):None
Buffers:
Acetate buffer pH 4 : Solution of 16.6% 0.05 M Sodium Acetate and 83.4% 0.05 M Acetic Acid
Phosphate buffer pH 7: Solution of 0.05 M Potassium Dihydrogenphosphate adjusted to pH 7 using 1 N Sodium Hydroxide
Borate buffer pH 9: Solution of 0.05 M Boric Acid and 0.05 M Potassium Chloride adjusted to pH 9 using 1 N Sodium Hydroxide
Details on test conditions:
TEST SYSTEM
- Sterilisation method: None
- Measures taken to avoid photolytic effects: During the test, the test substance and test substance solutions were protected from light.
- Measures to exclude oxygen: During the test, the test substance and test substance solutions were kept under nitrogen.
- If no traps were used, is the test system closed/open Open
- Is there any indication of the test material adsorbing to the walls of the test apparatus? No
TEST MEDIUM
- Kind and purity of water: Tap water purified by a Milli-Q water purification system
- Preparation of test medium: 5 ml of test substance was mixed with 10 and 25 ml of each buffer in a glass vessel. Each vessel was inverted 10 times by hand and the phases were allowed to separate. Four minutes and 1 hour after preparation, a sample was taken from the upper organic phase and analysed.

Duration:
4 min
pH:
4
Initial conc. measured:
10 other: ml
Duration:
4 min
pH:
7
Initial conc. measured:
10 other: ml
Duration:
4 min
pH:
9
Initial conc. measured:
10 other: ml
Duration:
1 h
pH:
4
Initial conc. measured:
25 other: ml
Duration:
1 h
pH:
7
Initial conc. measured:
25 other: ml
Duration:
1 h
pH:
9
Initial conc. measured:
25 other: ml
Number of replicates:
Total of 6:
3- 10 ml volume buffer solutions at pH 4, pH 7, pH 9
3- 25 ml volume buffer solutions at pH 4, pH 7, pH 9
Positive controls:
yes
Remarks:
untreated test substance
Negative controls:
no
Statistical methods:
The peak area of the major components with a retention time between 5 and 5.5 minutes was used as response in the calculations.
Degree of hydrolysis and relative concentration (%) calculated for each volume and pH.
Preliminary study:
Quick hydrolysis of OS1600 was expected. To confirm this, the above-explained test was conducted.
Test performance:
All results show a quick reaction of test substance with buffer. When using 10 ml buffer, hydrolysis rate is lower than when using 25 ml buffer. From this it is concluded that 10 ml buffer is limiting the reaction rate.
When using 25 ml buffer solution pH4, pH 7, pH 9, a > 50% decrease concentration was observed after 4 minutes which demonstrates that the half-life time of the test substance is < 4 minutes at room temperature.
Transformation products:
no
Details on hydrolysis and appearance of transformation product(s):
- Other: Quick hydrolysis of test substance was expected.
Key result
pH:
4
Temp.:
25 °C
DT50:
< 4 min
Key result
pH:
7
Temp.:
25 °C
DT50:
< 4 min
Key result
pH:
9
Temp.:
25 °C
DT50:
< 4 min
Details on results:
TEST CONDITIONS
- pH, sterility, temperature, and other experimental conditions maintained throughout the study: Yes
- Anomalies or problems encountered (if yes): No

MAJOR TRANSFORMATION PRODUCTS
At pH5:None
At pH7:None
At pH9:None

MINOR TRANSFORMATION PRODUCTS
Maximum concentrations in % of the applied amount
- at pH5:None
- at pH7:None
- at pH9:None


MINERALISATION (distinguish between dark and irradiated samples)
- % of applied radioactivity present as CO2 at end of study: None


INDICATION OF UNSTABLE TRANSFORMATION PRODUCTS:


VOLATILIZATION (at end of study)
- Evolved CO2 in % of the applied: .. at pH 5, .. at pH 7, .. at pH 9
- Total volatile organics in % of the applied: .. at pH 5, .. at pH 7, .. at pH 9


UNIDENTIFIED RADIOACTIVITY (at end of study)
- at pH4:None
- at pH7:None
- at pH9:None


PATHWAYS OF HYDROLYSIS
- Description of pathwayS:Not applicable
- Figures of chemical structures attached: No


SUPPLEMENTARY EXPERIMENT (if any): RESULTS: None

All results show a quick reaction of test substance with buffer. When using 10 ml buffer, hydrolysis rate is lower than when using 25 ml buffer. From this it is concluded that 10 ml buffer is limiting the reaction rate. When using 25 ml buffer solution pH4, pH 7, pH 9, a > 50% decrease concentration was observed after 4 minutes which demonstrates that the half-life time of the test substance is < 4 minutes at room temperature.

Validity criteria fulfilled:
yes
Conclusions:
The half-life time of the test substance at room temperature were determined to be < 4 minutes at pH 4, 7 and 9.
According to the guideline, the test susbstance is considered hydrolytically instable and no further tests are required.
Executive summary:

The hydrolysis test was performed in accordance with OECD Guideline 111. Test substance was mixed with acetate buffer pH4, phosphate buffer pH 7 and borate buffer pH 9 in a glass vessel at room temperature and protected from light. Each vessel was inverted 10 times by hand and the phases were allowed to separate. Four minutes and 1 hour after preparation, a sample was taken from the upper organic phase and analysed. Chromatograms of the pretreated samples were compared with a chromatogram of untreated test substance. All results show a quick reaction of test substance with buffer. When using 10 ml buffer, hydrolysis rate is lower than when using 25 ml buffer. From this it is concluded that 10 ml buffer is limiting the reaction rate. When using 25 ml buffer solution pH4, pH 7, pH 9, a > 50% decrease concentration was observed after 4 minutes which demonstrates that the half-life time of the test substance is < 4 minutes at room temperature. The half-life of test item at pH 4, 7 and 9 was therefore determined to be < 4 minutes.

Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
Conducted with the main hydrolysis product= MPKO.
Qualifier:
according to
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Deviations:
not specified
Qualifier:
according to
Guideline:
EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)
Deviations:
not specified
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
yes
Details on sampling:
The test substance was spiked to each of the buffer solutions at a nominal concentration of approximately 50 mg/L using a spike solution in water. for the test at pH 4, the peak areas of the test substance were determined immediately after preparation (t = 0) and at several sampling points after t = 0. The pH of the test samples was determined at the beginning and the end of the test. For the test at pH 7, the samples were prepared and placed in water baths at the end of the working day. The pH of the test samples was determined at the beginning and the end of the test.
Buffers:
Buffers: Acetate buffer pH 4: solution of 16.6 % 0.05 M sodium acetate and 83.4% 0.05 M acetic acid Phosphate buffer pH 7: solution of 0.05 M potassium di-hydrogenphosphate adjusted to pH 7 using 1 N sodium hydroxide Borate buffer pH 9: solution of 0.05 M boric acid and 0.05 M potassium chloride ajusted to pH 9 using 1 N sodium hydroxide
Duration:
120 h
pH:
7
Duration:
120 h
pH:
4
Preliminary study:
At pH 9, a decrease in concentration < 10% was observed after 120 hours. It demonstrate that the half-life time of the substance at 25 ºC > 1 year. According to the guideline, no further tests were required. At pH 4 and pH 7, a decrease in concentration > 10% after 120 hours was observed, and the main test was required. In order to determined reaction rate at 50 ºC, additional samples were taken at t= 261, 264 and 268 hours. After 268 hours of testing at 50 ºC, the relative concentration was still above 50%.
Key result
pH:
4
Temp.:
25 °C
DT50:
> 1 yr
Key result
pH:
7
Temp.:
25 °C
DT50:
> 1 yr
Key result
pH:
9
Temp.:
25 °C
DT50:
> 1 yr
Details on results:
At the end of the tests, concentrations became stable at 50-60% of the initial concentration. This shows that equilibrium if formed and that this is not hydrolysis. The tes substance was determined to be hydrolytically stable (i.e. half-life time of > 1 year at 35 ºC) at pH 4, 7 and 9.
Validity criteria fulfilled:
yes
Conclusions:
MPKO is therefore considered hydrolytically stable (i.e. half-life time of > 1 year at 25°C) at pH 4, pH 7 and pH 9.
Executive summary:

The hydrolysis test was performed in accordance with OECD Guideline 111 and EU Method C.7. In all tests performed, a decrease in concentration was observed. At the end of the main tests, concentrations became stable at 50 -60% of the initial concentration. This indicates that equilibrium is formed and that this is not hydrolysis. MPKO is therefore considered hydrolytically stable (i.e. half-life time of > 1 year at 25°C) at pH 4, pH 7 and pH 9.

Description of key information

The half-life time of the test substance at room temperature were determined to be < 4 minutes at pH 4, 7 and 9. A hydrolysis test was also performed on MPKO, the hydrolytic product of OS1600. MPKO was considered to be hydrolytically stable (i.e. half-life time of > 1 year at 25°C) at pH 4, pH 7 and pH 9.

Key value for chemical safety assessment

Half-life for hydrolysis:
4 min
at the temperature of:
20 °C

Additional information

Key study: The hydrolysis test was performed in accordance with OECD Guideline 111 (GLP study). The half-life of test item at pH 4, 7 and 9 and room temperature was < 4 minutes, and therefore, the substance was determined to be hydrolytically instable.

Supporting study: The hydrolysis test was performed with the analogue substance MPKO in accordance with OECD Guideline 111 (GLP study). In all tests performed, a decrease in concentration was observed. At the end of the main tests, concentrations became stable at 50 -60% of the initial concentration. This indicates that equilibrium is formed and that this is not hydrolysis. MPKO is therefore considered hydrolytically stable (i.e. half-life time of > 1 year at 25°C) at pH 4, pH 7 and pH 9.