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Hydrolysis

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Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2017-11-08 to 2018-04-05
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
equivalent or similar to guideline
Guideline:
EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)
Deviations:
no
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: D26-3-3-1
- Expiration date of the lot/batch: 2018-12-01
- Purity test date: no data
- Purity: 47.4 wt%

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: room temperature in the dark
- Stability under test conditions: no data
- Solubility and stability of the test substance in the solvent/vehicle: no data
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
- Sampling intervals for the parent/transformation products: Duplicate sample solutions were taken initially and from the water bath at various time points. The pH of each solution recorded. The concentration of test item in the sample solutions was determined by flow ionization-mass spectrometry.
- Sampling method: An aliquot of each sample solution was diluted by a factor of 100 using mobile phase.
Buffers:
- pH: 4.0, 7.0 and 9.0
- Type and final molarity of buffer:
pH Components Concentration (mol dm-3)
4 Citric acid 0.006
Sodium chloride 0.004
Sodium hydroxide 0.007
7 Disodium hydrogen orthophosphate (anhydrous) 0.003
Potassium dihydrogen orthophosphate 0.002
Sodium chloride 0.002
9 Disodium tetraborate 0.001
Sodium chloride 0.002
- The buffer solutions were passed through a 0.2 µm membrane filter to sterilize and subjected to ultrasonication and degassing with nitrogen to minimize dissolved oxygen.
Details on test conditions:
TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: individual glass vessels, sealed with minimal headspace
- Sterilisation method: The buffer solutions were passed through a 0.2 μm membrane filter to sterilize and subjected to ultrasonication and degassing with nitrogen to minimize dissolved oxygen.
- Lighting: These sample solutions were shielded from light whilst maintained at the test temperature.
- Measures taken to avoid photolytic effects: sample solutions were shielded from light
- Measures to exclude oxygen: degassing with nitrogen to minimize dissolved oxygen
- Is there any indication of the test material adsorbing to the walls of the test apparatus? no

TEST MEDIUM
- Preparation of test medium: Stock solutions of test item were prepared at a nominal concentration of 1.0 mg/L in the three buffer solutions. The stock solutions were adjusted to the nominal pH of the relevant buffer solution and then split into individual glass vessels, sealed with minimal headspace, for each data point. These sample solutions were shielded from light whilst maintained at the test temperature.
- Renewal of test solution: not applicable

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Dissolved oxygen: no data
Duration:
120 h
pH:
4
Temp.:
50 °C
Initial conc. measured:
>= 1 - <= 1 g/L
Duration:
120 h
pH:
7
Temp.:
50 °C
Initial conc. measured:
>= 0.972 - <= 0.984 g/L
Duration:
120 h
pH:
9
Temp.:
50 °C
Initial conc. measured:
>= 1.01 - <= 1.02 g/L
Number of replicates:
2
Positive controls:
no
Negative controls:
no
Statistical methods:
When the rate constant is known at two or more temperatures, the rate constant at other temperatures can be estimated using an Arrhenius plot. The natural logarithm of the rate constant and the reciprocal of the test temperature (K) for each individual determination were plotted for each pH, if relevant. From the regression line, the natural logarithm of the rate constant at 25 °C (1/T [K] = 3.354 x 10-3) was obtained and used to generate both the estimated rate constant and the half-life.
Preliminary study:
Sample solutions at pH 4, 7 and 9 were maintained at 50.0 ± 0.5 °C for a period of 120 hours.
Results from the Preliminary test/Tier 1 showed it was not necessary to undertake further testing at pH 4, 7 and 9.
Transformation products:
no
% Recovery:
>= 99.1 - <= 99.7
pH:
4
Temp.:
50 °C
Duration:
120 h
Remarks on result:
hydrolytically stable based on preliminary test
% Recovery:
>= 96.2 - <= 98.6
pH:
7
Temp.:
50 °C
Duration:
120 h
Remarks on result:
hydrolytically stable based on preliminary test
% Recovery:
>= 99 - <= 99.8
pH:
9
Temp.:
50 °C
Duration:
120 h
Remarks on result:
hydrolytically stable based on preliminary test
pH:
4
Temp.:
25 °C
DT50:
> 1 yr
Key result
pH:
7
Temp.:
25 °C
DT50:
> 1 yr
pH:
9
Temp.:
25 °C
DT50:
> 1 yr
Validity criteria fulfilled:
yes
Remarks:
No significant peaks were observed at the approximate retention time of the test item on analysis of any matrix blank solutions.
Conclusions:
According to OECD 111, the test substance was found to be hydrolytically stable at pH 4.0, pH 7.0 and pH 9.0 with an estimated half-life time higher than 1 year at 25°C. Therefore, no further testing was performed. The results of the test can be considered reliable without restriction.

Description of key information

One study (Walker, 2019) was performed according to OECD guideline 111 and regarded as a key study (Klimisch score of 1). A half-life time of > 1 year at 25 °C and pH 7 was determined for the test substance.

Key value for chemical safety assessment

Additional information