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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:
From 2000-12-12 to 2000-02-29
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
test procedure in accordance with national standard methods
Remarks:
Study conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of relevant results.
Qualifier:
according to
Guideline:
EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)
Deviations:
no
Principles of method if other than guideline:
Not applicable.
GLP compliance:
yes (incl. certificate)
Remarks:
1998-07-21
Specific details on test material used for the study:
No additional information
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
- Sampling intervals for the parent/transformation products: 2.4, 5.5, 24, 28, 48, 53, 120 h
- Sampling method: an aliquot (50.0 mL) of each sample was extracted with 3 protions of dichloromethane. Each extract being filtered through anhydrous sodium sulphate. The combined extracts were evaporated to dryness and the residue re-dissolved on methanol.
- Sampling methods for the volatile compounds, if any: not applicable.
- Sampling intervals/times for pH measurements: no data
- Sampling intervals/times for sterility check: no data
- Sample storage conditions before analysis: no data
- Other observation, if any (e.g.: precipitation, color change etc.): none.
Buffers:
- pH: 4, 7, and 9
- Composition of buffer:
pH 4:
- Citric acid 0.05 mol/L
- sodium hydroxide 0.10 mol/L
- hydrochloric acid 0.05 mol/L
pH 7:
- Disodium hydrogen orthophosphate 0.04 mol/L
- Potassium dihydrogen orthophosphate 0.03 mol/L
pH 9:
- Disodium tetraborate 0.05 mol/L
- hydrochloric acid 0.02 mol/L
Estimation method (if used):
Not applicable
Details on test conditions:
TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: glass flasks.
- Sterilisation method: no data
- Lighting: no
- Measures taken to avoid photolytic effects: Test solutions were shielded from light
- Measures to exclude oxygen: Solutions were subjected to ultrasonication and degassing to minimise dissolved oxygen content.
- Details on test procedure for unstable compounds: not applicable
- Is there any indication of the test material adsorbing to the walls of the test apparatus? no
TEST MEDIUM
- Volume used/treatment no data
- Kind and purity of water: no data
- Preparation of test medium: no data
- Renewal of test solution: no data
- Identity and concentration of co-solvent: no data
Positive controls:
yes
Negative controls:
no
Statistical methods:
not applicable
Preliminary study:
Preliminary study demonstrated that hydrolysis of test substance occured only at pH 9 at 50°C.
Transformation products:
not specified
Details on hydrolysis and appearance of transformation product(s):
No data
Key result
pH:
4
Temp.:
25 °C
DT50:
> 1 yr
Type:
not specified
Remarks on result:
other: estimated
Key result
pH:
7
Temp.:
25 °C
DT50:
> 1 yr
Type:
not specified
Remarks on result:
other: estimated
Key result
pH:
9
Temp.:
25 °C
Hydrolysis rate constant:
0.003 h-1
DT50:
228 h
Type:
not specified
Other kinetic parameters:
None
Details on results:
cf. table in "Any other information on results"

Table 1: Hydrolysis at pH 9 at 50°C, from the preliminary test

Time (h)

0

5.5

24

28

48

53

73

96

Concentration (g/L) x10²

9.76

8.82

5.22

4.57

3.21

2.95

1.80

1.18

Log10 [concentration (g/L]

-1.011

-1.054

-1.282

-1.340

-1.493

-1.531

-1.744

-1.928

% of initial

100

90.4

53.5

46.9

32.9

30.2

18.5

12.1

Table 2: Hydrolysis at pH9 at 40°C

Time (h)

0

48

72

96

Concentration (g/L) x10²

10.1

5.84

4.61

3.75

Log10 [concentration (g/L]

-0.996

-1.234

-1.337

-1.426

% of initial

-

58

46

37

Validity criteria fulfilled:
yes
Conclusions:
The rate constant and half-life at 25°C at pH 9 were:
- k= 3.04x10-3 h-1
- t1/2= 228 h
Executive summary:

The experiment conducted under GLP, and following EU guidelines, demonstated that hydrolysis of the test substance is:

pH

Rate constant (s-1)

Half-life at 25°C

4

-

> 1 year (estimated)

7

-

> 1 year (estimated)

9

8.45 x 10-7

228 hours

Description of key information

EU Method C.7, GLP, K, rel. 1:

- Rate constant at 25°C and pH 9 = 8.45x10-7 s-1

- Half-life at 25°C and pH 9 = 228 hours

Key value for chemical safety assessment

Half-life for hydrolysis:
228 h
at the temperature of:
25 °C

Additional information

One key study is available, according to EU Method C.7 with GLP statement, to assess the hydrolysis of the registered substance. The experiment was conducted at three different pH (4, 7 and 9). The half-life at pH 4 and at pH 7 (25°C) are estimated to be greater than 1 year. The rate constant and half-life at pH 9 (25°C) are 8.45 x 10-7s-1and 228 hours, respectively (see table below).

pH

Rate constant (s-1)

Half-life at 25°C

4

-

> 1 year (estimated)

7

-

> 1 year (estimated)

9

8.45 x 10-7

228 hours