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Environmental fate & pathways

Hydrolysis

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Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
SUB-C-2114439301-60-01/F
Qualifier:
according to
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
- Sampling intervals for the parent substance: Samples taken immediately, and then after 2.4, 24 and 120 hours.
- Sampling method: At each sampling time, two samples were removed from the oven and an aliquot (2 mL) of each was diluted to volume (20 mL) with acetone. The samples were filtered (0.45 μm, PTFE) before analysis by gas chromatography (GC).
- Sampling methods for the volatile compounds, if any: Not applicable
- Sampling intervals/times for pH measurements: pH and temperature measured at the start and end of test.
- Sampling intervals/times for sterility check: Not required as only preliminary phase conducted and no evidence of hydrolysis was observed.
- Sample storage conditions before analysis: Samples analysed immediately.
- Other observation, if any (e.g.: precipitation, color change etc.): None specified.
Buffers:
pH 4: 0.2M aqueous potassium dihydrogen orthophosphate (110 mL) was mixed with 0.07M aqueous disodium hydrogen orthophosphate dodecahydrate (250 mL) and purified water (640 mL). The pH was adjusted to 4.0 ± 0.05 with orthophosphoric acid.

pH 7: 0.2M aqueous potassium dihydrogen orthophosphate (500 mL) was mixed with 1M sodium hydroxide (60 mL) and purified water (1440 mL). The pH was measured as 7.0 ± 0.05.

pH 9: 0.1M boric acid in 0.1M aqueous potassium chloride (1000 mL) was mixed with 1M sodium hydroxide (42 mL) and purified water (958 mL). The pH was adjusted to 9.0 ± 0.05 with 1M sodium hydroxide.
Estimation method (if used):
Not applicable
Details on test conditions:
TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: Glass wheaton vials (10 mL)
- Sterilisation method: Standard cleaning practices
- Lighting: Samples incubated in darkness
- Measures taken to avoid photolytic effects: Samples incubated in darkness
- Measures to exclude oxygen: Buffer solutions purged with Nitrogen before use.
- If no traps were used, is the test system closed/open: Test system closed with crimp-seals. Stock solutions and samples taken through the septum to minimise volatilisation.
- Is there any indication of the test material adsorbing to the walls of the test apparatus? None noted.

TEST MEDIUM
- Volume used/treatment: 1 mL of a stock solution (8 g/L) of the substance in water.
- Kind and purity of water: Purified water.
- Preparation of test medium: Not applicable
- Renewal of test solution: Not applicable
- Identity and concentration of co-solvent: No co-solvent used.

OTHER TEST CONDITIONS
- Adjustment of pH: The pH of the buffer solutions were adjusted before use as required. No pH adjusment was required after test solutions added.
- Dissolved oxygen: Not specified
Duration:
5 d
pH:
4
Temp.:
50 °C
Initial conc. measured:
>= 738.1 - <= 763.6 mg/L
Duration:
5 d
pH:
7
Temp.:
50 °C
Initial conc. measured:
>= 832 - <= 842.8 mg/L
Duration:
5 d
pH:
9
Temp.:
50 °C
Initial conc. measured:
>= 759.9 - <= 804.9 mg/L
Number of replicates:
Sampled in duplicate
Positive controls:
no
Negative controls:
no
Statistical methods:
Not a guideline requirement
Preliminary study:
The preliminary study showed that at each of pH 4, 7 and 9 and 50 ± 0.5ºC, less than 10% hydrolysis had occurred after 120 hours (5 days), equivalent to a half-life of greater than 1 year under environmental conditions (25°C). No further testing was considered necessary.
Test performance:
The test was adequately performed meeting the OECD 111 Guideline requirements.
Transformation products:
no
Details on hydrolysis and appearance of transformation product(s):
Substance was hydrolytically stable and therefore transformation products not considered.
pH:
4
Temp.:
50 °C
Duration:
5 d
Remarks on result:
hydrolytically stable based on preliminary test
pH:
7
Temp.:
50 °C
Duration:
5 d
Remarks on result:
hydrolytically stable based on preliminary test
pH:
9
Temp.:
50 °C
Duration:
5 d
Remarks on result:
hydrolytically stable based on preliminary test
pH:
4
Temp.:
25 °C
DT50:
> 1 yr
Remarks on result:
hydrolytically stable based on preliminary test
pH:
7
Temp.:
25 °C
DT50:
> 1 yr
Remarks on result:
hydrolytically stable based on preliminary test
pH:
9
Temp.:
25 °C
DT50:
> 1 yr
Remarks on result:
hydrolytically stable based on preliminary test
Details on results:
TEST CONDITIONS
- pH, sterility, temperature, and other experimental conditions maintained throughout the study: Yes
- Anomalies or problems encountered (if yes): None encountered.

No transformation products (major or minor) observed and test sample recoveries within the range of 90 to 110% of nominal.


Results with reference substance:
Not applicable

Preliminary test results:

 

Ct (mg/L)

pH

t0h

t2.4h

t24h

t120h

 

Measured

Mean

Measured

Mean

Measured

Mean

Measured

Mean

 

 

 

 

 

 

 

 

 

4

760, 740

750

770, 820

790

800, 740

770

810, 790

800

 

 

 

 

 

 

 

 

 

7

840, 830

840

840, 770

810

790, 800

790

770, 790

780

 

 

 

 

 

 

 

 

 

9

800, 760

780

780, 740

760

780, 870

830

770, 840

810

 

 

 

 

 

 

 

 

 

 

where Ctis the concentration of MTBE in solution at time th(in hours)

Values in the summary table are presented to 2 significant figures. The mean values were calculated from unrounded data.

Validity criteria fulfilled:
yes
Conclusions:
The test substance was determined to be hydrolytically stable under acidic, neutral and basic conditions as determined in a preliminary test. The half-life is considered to be greater than 1 year under environmental conditions (25°C) and accordingly no further testing was deemed necessary.

Description of key information

The test substance was determined to be hydrolytically stable under acidic, neutral and basic conditions as determined in a preliminary test conducted in accordance with the OECD guideline (Key study). The half-life is considered to be greater than 1 year under environmental conditions (25°C) and accordingly no further testing was deemed necessary. No key value for chemical safety assessment is appropriate.

A supporting publication also shows that the substance is hydrolytically stable under environmentally relevant conditions.

Key value for chemical safety assessment

Additional information