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Environmental fate & pathways

Hydrolysis

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Administrative data

Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
13.01.2005-15.03.2005
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2005
Report Date:
2005

Materials and methods

Test guidelineopen allclose all
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)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid

Study design

Analytical monitoring:
yes
Details on sampling:
- Sampling intervals for the parent/transformation products: samples were taken at the beginning of the test and after 24, 48, 72, 120, 144, and 168 h at pH 4, 7, and 9 at 50°
- Sampling method: sampling was performed by adding the same volume acetonitrile (5 mL) with 2% glacial acetic acid directly to the incubation vessels and direct injection of the sample
- Sampling intervals/times for pH measurements: pH of test solution was determined at the beginning of the test and after 24, 48, 72, 120, 144, and 168 h at pH 4, 7, and 9 at 50°
Buffers:
- pH: 4, 7, and 9
- Type and final molarity of buffer: 0.05 M citrate buffer (pH 4), 0.05 M phosphate buffer (pH 7), and 0.05 M borate buffer (pH 9) according to EC method C.7 (92/69/EC), OECD guideline 111 and/or BBA Merkblatt Nr. 55, Teil I
- Composition of buffer: not reported, but buffer systems selected according to EC method C.7 (92/69/EC), OECD guideline 111 and/or BBA Merkblatt Nr. 55, Teil I
Details on test conditions:
TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: amber glass vials (volume: 20 mL) closed with PTFE sealed screw caps
- Sterilisation method: not reported
- Measures taken to avoid photolytic effects: photolytic interference was avoided (amber glass vials)
- Measures to exclude oxygen: all suitable precautions were taken to exclude dissolved oxygen: bubbling the solution with helium for five minutes before preparing the test solution
- Details of traps for volatile, if any: no traps used
- If no traps were used, is the test system closed/open: the system was closed with PTFE sealed screw caps
- Is there any indication of the test material adsorbing to the walls of the test apparatus? no
TEST MEDIUM
- Volume used/treatment: 5 mL
- Kind and purity of water: bi-distilled grade
- Preparation of test medium: The test item was dissolved in acetone (100 mg/L). 0.5 mL of this stock solution were transferred to a series of 20 mL glass vials. The solvent was evaporated under a fume hood at ambient temperature overnight. Afterwards, 5 mL of the selected buffer was added to each vial. The vials were closed with PTFE sealed screw caps. The concentration did not exceed 0.01 M at the test temperature. The nominal concentrations were 10 mg/L at pH 4, 7, and 9.
- Renewal of test solution: no
- Identity and concentration of co-solvent: acetone was used to prepare the stock solution (100 mg test item/L); after transferring 0.5 ml of this stock solution to the test vials the solvent was evaporated (no further solvents used in the test)
OTHER TEST CONDITIONS
- Adjustment of pH: no
- Dissolved oxygen: all suitable precautions were taken to exclude dissolved oxygen: bubbling the solution with helium for five minutes before preparing the test solution
Duration of testopen allclose all
Duration:
7 d
pH:
4
Temp.:
50 °C
Initial conc. measured:
7.37 mg/L
Duration:
7 d
pH:
7
Temp.:
50 °C
Initial conc. measured:
7.45 mg/L
Duration:
7 d
pH:
9
Temp.:
50 °C
Initial conc. measured:
8.17 mg/L
Number of replicates:
All measurements were carried out in duplicate (no further informations)

Results and discussion

Preliminary study:
Only the preliminary test was carried out.
Test performance:
In a preliminary test conducted according to OECD Guideline 111 and EU-Method C.7 the hydrolysis of the test item as a function of pH was investigated.
Transformation products:
yes
Identity of transformation productsopen allclose all
No.:
#1
Reference
Reference substance name:
Unnamed
No.:
#2
Reference
Reference substance name:
Unnamed
Details on hydrolysis and appearance of transformation product(s):
- Formation and decline of each transformation product during test: mono-, di-, and triester were detected; the tri-esters were rapidly degraded to di-esters, which sequentially degrade to the mono-esters
- Pathways for transformation: ester cleavage
Dissipation DT50 of parent compoundopen allclose all
pH:
4
Temp.:
50 °C
Hydrolysis rate constant:
0.01 h-1
DT50:
27.3 d
Type:
(pseudo-)first order (= half-life)
pH:
7
Temp.:
50 °C
Hydrolysis rate constant:
0.01 h-1
DT50:
72.3 h
Type:
(pseudo-)first order (= half-life)
pH:
9
Temp.:
50 °C
Hydrolysis rate constant:
0.01 h-1
DT50:
47.8 h
Type:
(pseudo-)first order (= half-life)
pH:
4
Temp.:
25 °C
Hydrolysis rate constant:
0.69 a-1
DT50:
> 1 yr
Type:
(pseudo-)first order (= half-life)
pH:
7
Temp.:
25 °C
Hydrolysis rate constant:
0.01 h-1
DT50:
17 d
Type:
(pseudo-)first order (= half-life)
pH:
9
Temp.:
25 °C
Hydrolysis rate constant:
0.01 h-1
DT50:
11.3 d
Type:
(pseudo-)first order (= half-life)

Any other information on results incl. tables

1. Time course of partially unsaturated TEA-EQ at pH 4, 7, and 9 and 50°C

a. Time course of partially unsaturated TEA-EQ at pH 4 and 50°C

Time (h)

pH

Actual concentration (mg/L)

Actual concentration in (%) of initial conc.

0

24

48

72

120

144

168

4.02

4.00

4.02

4.00

4.00

4.00

4.00

7.37

7.24

6.85

7.09

3.58*

7.03

5.69

100

98.3

92.9

96.2

48.7*

95.5

77.2

Mean

Std. Deviation

RSD

4.01

0.01

0.25

*discarded as an outliner

b. Time course of partially unsaturated TEA-EQ at pH 7 and 50°C

Time (h)

pH

Actual concentration (mg/L)

Actual concentration in (%) of initial conc.

0

24

48

72

120

144

168

7.06

7.03

7.00

7.00

6.99

6.99

6.98

7.45

4.37

3.12

3.38

0.887*

1.59

1.25

100

58.7

41.9

45.3

11.9*

21.3

16.7

Mean

Std. Deviation

RSD

7.01

0.03

0.43

*discarded as an outliner

c. Time course of partially unsaturated TEA-EQ at pH 9 and 50°C

Time (h)

pH

Actual concentration (mg/L)

Actual concentration in (%) of initial conc.

0

24

48

72

120

144

168

9.03

9.01

9.04

9.04

9.03

9.01

9.03

8.17

3.54

2.89

1.84

0.486*

0.767

0.590

100

43.3

35.4

22.5

5.9*

9.4

7.2

Mean

Std. Deviation

RSD

9.03

0.01

0.11

*discarded as an outliner

The temperature during the entire period of the test was measured to be 50.0 to 50.2°C

The results from the 120 h sampling were regarded as artefact, and therefore excluded from the analysis. As a consequence, the measurement was extended to 168 h test duration.

2. Rate constants and half-lives at 50 and 25°C

pH 4

pH 7

pH 9

50°C

Kobs (h)

0.00106

0.00958

0.01449

t1/2 (h)

654

72.3

47.8

t1/2 (d)

27.3

3.01

1.99

25°C

Kobs (h)

0.000187

0.00169

0.00256

t1/2 (h)

3700

409

271

t1/2 (d)

154.2

17.0

11.3

The degradation rate was calculated according to the assumption of Arrhenius.

At pH 4 and 50°C, the degradation of the main component of partially unsaturated TEA-EQ was less than 10% over a period of 120 h. The corresponding half-life at 25°C is therefore assumed to be above one year (default assumption acc. to guidelines). In contrast, at pH 7 and 9 and 50°C, more than 10% of the test item were hydrolysed within 120 h. Based on the results half-lives of 17 (pH 7) and 11.3 d (pH 9) were deduced from the reaction rate constants at 25°C.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Conclusions:
The hydrolysis of partially unsaturated TEA-EQ as a function of pH was investigated in a study conducted according to OECD Guideline 111 and EU-method C.7. (Preliminary test; main test not conducted due to the pronounced biodegradability of the test substance). At pH 4 and 50°C, the degradation of the main component of partially unsaturated TEA-EQ was less than 10% over a period of 120 h. The corresponding half-life at 25°C is therefore assumed to be above one year (default assumption acc. to guidelines). In contrast, at pH 7 and 9 and 50°C, more than 10% of the test item were hydrolysed within 120 h. Based on the results half-lives of 17 (pH 7) and 11.3 d (pH 9) were deduced from the reaction rate constants at 25°C. Di- and mono-ester were detected as degradation products.
Executive summary:

The hydrolysis of partially unsaturated TEA-EQ as a function of pH was investigated in a study conducted according to OECD Guideline 111 and EU-method C.7. (Preliminary test; main test not conducted due to the pronounced biodegradability of the test substance).

The following results were obtained:

Hydrolysis of partially unsaturated TEA-EQ at 50°C

pH

Temperature (°C)

Rate constant

t1/2

4

50

0.00106 1/h

27.3 d

7

50

0.00958 1/h

72.3 h

9

50

0.01449 1/h

47.8 h

Hydrolysis of partially unsaturated TEA-EQ at 25°C

pH

Temperature (°C)

Rate constant

t1/2

4

25*

0.693 1/a

>1 a*

7

25

0.00169 1/h

17.0 d

9

25

0.00256 1/h

11.3 d

* default assumption acc. to guideline

At pH 4 and 50°C, the degradation of the main component of partially unsaturated TEA-EQ was less than 10% over a period of 120 h. The corresponding half-life at 25°C is therefore assumed to be above one year (default assumption acc. to guidelines). In contrast, at pH 7 and 9 and 50°C, more than 10% of the test item were hydrolysed within 120 h. Based on the results half-lives of 17 (pH 7) and 11.3 d (pH 9) were deduced from the reaction rate constants at 25°C. Di- and mono-ester were detected as degradation products.