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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
Study period:
13.02-30.04.2013
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
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:
no
Details on sampling:
- Sampling method: The samples were taken from the water bath at various times and the pH of each sample recorded.
- Sampling methods for the volatile compounds, if any: no
- Sampling intervals/times for pH measurements: 0, 24, 120 hours
- Other observation, if any (e.g.: precipitation, colour change etc.): no
Buffers:
-ph 4:
Potassium hydrogen phthalate 5 mmol dm-3
pH 7:
Disodium hydrogen orthophosphate (anhydrous) 3 mmol dm-3
Potassium dihydrogen orthophosphate 2 mmol dm-3
Sodium chloride 2 mmol dm-3
pH 9:
Disodium tetraborate 1 mmol dm-3
Sodium chloride 2 mmol dm-3
Details on test conditions:
TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: stoppered glass vessels
- Lighting: the solutions were shielded from light whilst maintained at the test temperature
- Measures taken to avoid photolytic effects: not reported
- Measures to exclude oxygen: ultrasonication and degassing with nitrogen
- Details on test procedure for unstable compounds: not applicable
- Details of traps for volatile, if any: not applicable
- If no traps were used, is the test system closed/open: closed
- Is there any indication of the test material adsorbing to the walls of the test apparatus? no
TEST MEDIUM
- Volume used/treatment: not reported
- Kind and purity of water: sterile buffer solution
- Preparation of test medium: Sample solutions were prepared in stoppered glass vessels at a nominal concentration of 400 mg/L in the three buffer solutions. The solutions were then adjusted to the respective nominal buffer solution pH, as necessary, with 0.1 M sodium hydroxide solution. The test solutions were split into individual vessels for each data point.
- Renewal of test solution: no
OTHER TEST CONDITIONS
- Adjustment of pH: adjusted to the respective nominal buffer solution pH, as necessary, with 0.1 M sodium hydroxide solution
- Dissolved oxygen: solutions were subjected to ultrasonication and degassing with nitrogen to minimize dissolved oxygen content
Duration:
0 h
pH:
4
Temp.:
50
Initial conc. measured:
0.378 mg/L
Duration:
0 h
pH:
4
Temp.:
50
Initial conc. measured:
0.391 mg/L
Duration:
0 h
pH:
7
Temp.:
50
Initial conc. measured:
0.4 mg/L
Duration:
0 h
pH:
7
Temp.:
50
Initial conc. measured:
0.421 mg/L
Duration:
0 h
pH:
9
Temp.:
50
Initial conc. measured:
0.407 mg/L
Duration:
0 h
pH:
9
Temp.:
50
Initial conc. measured:
0.349 mg/L
Number of replicates:
2 per pH and per sampling date
Positive controls:
not specified
Negative controls:
not specified
Statistical methods:
no
Preliminary study:
Preliminary Test/Tier 1: Sample solutions at pH 4, 7 and 9 were maintained at 50.0 ± 0.5 °C for a period of 5 days.
Test Tier 2: Results from the Preliminary Test/Tier 1 showed it was not necessary to undertake further testing at pH 4, 7 and 9.
Transformation products:
not specified
% Recovery:
99.6
St. dev.:
2
pH:
4
Temp.:
50 °C
Duration:
24 h
% Recovery:
98.2
St. dev.:
0.4
pH:
4
Temp.:
50 °C
Duration:
120 h
% Recovery:
98
St. dev.:
0.2
pH:
7
Temp.:
50 °C
Duration:
24 h
% Recovery:
92.3
St. dev.:
3.2
pH:
7
Temp.:
50 °C
Duration:
120 h
% Recovery:
104.5
St. dev.:
2.1
pH:
9
Temp.:
50 °C
Duration:
24 h
% Recovery:
102
St. dev.:
2.8
pH:
9
Temp.:
50 °C
Duration:
120 h
pH:
4
Temp.:
50 °C
DT50:
> 1 yr
Type:
not specified
pH:
7
Temp.:
50 °C
DT50:
> 1 yr
Type:
not specified
pH:
9
Temp.:
50 °C
DT50:
> 1 yr
Type:
not specified
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: not the purpose of the study

MINOR TRANSFORMATION PRODUCTS: not the purpose of the study

Table 1 Mean recovery of the test item in different pH buffer solutions (recalculated)

pH Time (Hours) Concentration (g/L) % of initial
A B mean SD
4 24 98.2 101 99.6 2.0
4 120 98.4 97.9 98.15 0.4
7 24 98.1 97.8 97.95 0.2
7 120 94.6 90.1 92.35 3.2
9 24 106 103 104.5 2.1
9 120 100 104 102 2.8
Validity criteria fulfilled:
yes
Conclusions:
In a valid, reliable and conclusive study according to OECD TG 111 (2004), the hydrolysis behaviour of Methyl phosphonic acid 70 % has been determined. The results are summarized as follows:
pH 4: estimated half-life at 25 °C >1 year
pH 7: estimated half-life at 25 °C >1 year
pH 9: estimated half-life at 25 °C >1 year
Executive summary:

In a valid, reliable and conclusive study, the hydrolysis behaviour of Methyl phosphonic acid 70 % has been determined. Assessment of hydrolytic stability was carried out using a procedure designed to be compatible with Method 111 of the OECD Guidelines for Testing of Chemicals, 13 April 2004. The results are summarized below:

pH 4: estimated half-life at 25 °C >1 year

pH 7: estimated half-life at 25 °C >1 year

pH 9: estimated half-life at 25 °C >1 year

Description of key information

With estimated half-lives at pH 4, 7, and 9 of >1 year (at 25 °C), the substance is considered as hydrolytically stable under environmental conditions.

Key value for chemical safety assessment

Half-life for hydrolysis:
1 yr
at the temperature of:
25 °C

Additional information

In a valid, reliable and conclusive study, the hydrolysis behaviour of Methyl phosphonic acid 70 % has been determined. Assessment of hydrolytic stability was carried out using a procedure designed to be compatible with Method 111 of the OECD Guidelines for Testing of Chemicals. The results are summarized below:

pH 4: estimated half-life at 25 °C >1 year

pH 7: estimated half-life at 25 °C >1 year

pH 9: estimated half-life at 25 °C >1 year