Registration Dossier

Environmental fate & pathways

Hydrolysis

Currently viewing:

Administrative data

Link to relevant study record(s)

Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
14 June 2007 to 07 August 2007
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)
Deviations:
no
Qualifier:
according to
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
Not applicable.
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
Choice of Concentration
The optimal concentration of the test item required for the analysis is lower than 10.3 g/l. This value is less than half of the solubility in water (project 20060734.01: cs = 396.7 g/l without correction for the purity) and less than 0.01 mol/l for the test item. This complies with the requirements of the guidelines.

Pretests
The pretests were done at 50 ± 0.5 °C with buffers at pH 4, 7 and 9.

Test1 at 50°C
Test 1 at 50 ± 0.5 °C was done with the buffer at pH 7. At least 6 aliquots were taken between a decomposition rate of 10 and 90 %.

Test1 at 20°C
Test 1 at 20 ± 0.5 °C was done with the buffer at pH 7. At least 6 aliquots were taken between a decomposition rate of 10 and 90 %.

Test1 at 60°C
Test 1 at 60 ± 0.5 °C was done with the buffer at pH 7. At least 6 aliquots were taken between a decomposition rate of 10 and 90 %.

Buffers:
Hydrochloric acid, Merck Sodium hydroxide, Riedel de Haen Buffers:
-pH 4: 21.01 g citric acid monohydrate were dissolved in 200 ml sodium hydroxide solution (c= 1 mol/l). This solution was filled up to a volume of 1000 ml with distilled water. 44 ml of hydrochloric acid (c = 1 mol/l) were added to 560 ml of this solution and filled up to a volume of 1000 ml with distilled water. The pH value was adjusted to pH 4 for each hydrolysis temperature.
-pH 7: 13.61 g potassium dihydrogen phosphate were dissolved in 1000 ml distilled water. 30 ml of sodium hydroxide solution (c = 1 mol/l) were added to 500 ml of this solution and filled up to a volume of 1000 ml with distilled water. The pH value was adjusted to pH 7 for each hydrolysis temperature.
-pH 9: 7.46 g potassium chloride and 6.18 g boric acid were dissolved in 1000 ml distilled water. 21 ml of sodium hydroxide solution (c = 1 mol/l) were added to 500 ml of this solution and filled up to a volume of 1000 ml with distilled water. The pH value was adjusted to pH 9 for each hydrolysis temperature.
Estimation method (if used):
Not conducted.
Details on test conditions:
Preparation of the Test Samples
For each test stock solutions of the test item were prepared by weighing about 19.8 mg to 26.5 mg of the test item and dissolving it in 50 ml of the relevant buffers. This preparation was done in a glove box filled with nitrogen.

Hydrolysis Procedure
The flasks containing the hydrolysis mixtures were placed in a thermostatically controlled water bath at the selected temperature for the specified time. Thereafter aliquots of each flask were taken and cooled down. The volumetric flasks were flooded with nitrogen again. The aliquots were stored in the refrigerator until their measurement.
The pH was controlled and the concentration of the unhydrolysed test item (main compound) was measured by HPLC.

Pretests
The pretests were done at 50 ± 0.5 °C with buffers at pH 4, 7 and 9.

Pretests
The pretests were done at 50 ± 0.5 °C with buffers at pH 4, 7 and 9.

Test1 at 50°C
Test 1 at 50 ± 0.5 °C was done with the buffer at pH 7. At least 6 aliquots were taken between a decomposition rate of 10 and 90 %.

Test1 at 20°C
Test 1 at 20 ± 0.5 °C was done with the buffer at pH 7. At least 6 aliquots were taken between a decomposition rate of 10 and 90 %.

Test1 at 60°C
Test 1 at 60 ± 0.5 °C was done with the buffer at pH 7. At least 6 aliquots were taken between a decomposition rate of 10 and 90 %.
Duration:
5 d
pH:
4
Temp.:
50
Initial conc. measured:
498.3 - 505.5 mg/L
Duration:
5 d
pH:
9
Temp.:
50
Initial conc. measured:
218.1 - 330 mg/L
Duration:
30.3 h
pH:
7
Temp.:
50
Initial conc. measured:
400.7 mg/L
Duration:
839.7 h
pH:
7
Temp.:
20
Initial conc. measured:
435.4 mg/L
Duration:
4 h
pH:
7
Temp.:
60
Initial conc. measured:
397.9 mg/L
Number of replicates:
2
Positive controls:
no
Negative controls:
no
Statistical methods:
The concentrations of the standards were calculated from the sample weights. The initial concentrations Co of the test item and the concentrations during the test process Ct were calculated from the HPLC software.
In the case of pseudo first order reaction, according to the following relationships a linear dependence on the time (t) is expected for log (Ct/Co): log (Ct/Co) = t * (-kobs) / 2.303
The experimental data of test 1 were checked graphically for the approximate fulfillment of this relationship. The constant kobs was determined by linear regression of - log (Ct/Co) to t.
The half-life period t½ was calculated according to: t½ = In2 / Kobs
The Arrhenius-equation was used to extrapolate the rate constants at higher temperature to room
temperature: In kT = - E/R * 1/T + const.
The constant "E/R" and "const." were determined by linear regression of 1/T to in Kobs
Preliminary study:
The decomposition at pH 4 is below 50 % after 2.4 hours and below 10 % after 5 days at 50 °C. According to Guideline 67/548/EEC Annex V no additional tests have to be performed for pH 4.

The decomposition at pH 9 is above 50 % after 2.4 hours at 50 °C. According to Guideline 67/548/EEC Annex V no additional tests have to be performed for pH 9.

The decomposition at pH 7 is below 50 % after 2.4 hours at 50 °C and above 10 % after 5 days at 50 °C. The pretest at pH 7 indicates that an examination of the hydrolysis kinetics is essential.
Test performance:
The test performed within the parameters of the guideline.
Transformation products:
not measured
Details on hydrolysis and appearance of transformation product(s):
Not applicable.
pH:
7
Temp.:
25 °C
DT50:
18.9 d
Type:
(pseudo-)first order (= half-life)
pH:
4
Temp.:
50 °C
DT50:
> 1 yr
Remarks on result:
other: Hydrolytically stable
pH:
9
Temp.:
50 °C
DT50:
< 2.4 h
Remarks on result:
other: Hydrolytically unstable
Other kinetic parameters:
None measured.
Details on results:
At pH 7 the half-life period was determined by extrapolation of the results of the experiments at 50 °C, 20 °C and 60 °C to a temperature of 25 °C. It was found to be 18.9 days.

At pH 4 less than 10 % of the reaction is observed after 5 days at 50 °C (t1/2 at 25 °C > 1 year). Thus the test substance may be considered hydrolytically stable and according to Guideline 67/548/EEC Annex V no additional testing is required.

At pH 9 more than 50 % of the reaction is observed after 2.4 hours at 50 °C. Thus the test substance may be considered hydrolytically unstable and according to Guideline 67/548/EEC Annex V no additional testing is required.

Summary of the hydrolysis results and extrapolation

Temperature in ⁰C

t½

in h

K

in h-1

Experiment

50

12.0

0.0576

Experiment 7

50

12.5

0.0555

Experiment 8

20

1003

0.0007

Experiment 9

20

1003

0.0007

Experiment 10

60

3.7

0.1893

Experiment 11

60

3.6

0.1923

Experiment 12

25⁰C

453

0.0015

Extrapolation

Regression: In kobs= -E/R * 1/T+const with – E/R = b and T in K

                                        b = -13771

                                        const = 39.7

                                        coefficient of determination r2= 0.9999

                                        t½at 25⁰C = 453 hours = 18.9 days

 

Results of the hydrolysis pre-tests (experiments 1 to 6)

Experiment

pH

Duration

Coin mg/l

Ctin mg/l

Ct/ Co

Decomposition in %

1

4

2.4h

498.3

497.4

0.9982

0.2

5d

454.4

0.9118

8.8

2

4

2.4h

505.5

506.4

1.0017

-0.2

5d

461.1

0.9120

8.8

3

7

2.4h

526.4

462.5

0-8785

12.2

5d

45.2

0.0858

91.4

4

7

2.4h

485.5

427.1

0.8798

12.0

5d

41.6

0.0857

91.4

5

9

2.4h

330.0

42.9

0.1300

87.0

5d

30.9

0.0938

90.6

6

9

2.4h

218.1

41.1

0.1882

81.2

5d

39.4

0.1805

82.0

 

Validity criteria fulfilled:
yes
Conclusions:
At pH 7 the half-life period was determined by extrapolation of the results of the experiments at 50 °C, 20 °C and 60 °C to a temperature of 25 °C. It was found to be 18.9 days.

At pH 4 less than 10 % of the reaction is observed after 5 days at 50 °C (t y2 at 25 °C > 1 year). Thus the test substance may be considered hydrolytically stable and according to Guideline 67/548/EEC Annex V no additional testing is required.

At pH 9 more than 50 % of the reaction is observed after 2.4 hours at 50 °C. Thus the test substance may be considered hydrolytically unstable and according to Guideline 67/548/EEC Annex V no additional testing is required.
Executive summary:

The objective of this study was the determination of the abiotic degradation of the test item, the determination of the hydrolysis rate as a function of the pH-value according to the consolidated version of Guideline 67/548/EEC Annex V (Council Directive 92/69/EEC) Part C: Methods for determination of ecotoxicity. C.7. abiotic degradation: hydrolysis as a function of pH and OECD test guidelines No. 111 (2004), Hydrolysis as a function of pH. Study performed in accordance with the Principles of Good Laboratory Practice (GLP) and reported with a GLP certificate.

 

At pH 7the half-life period was determined by extrapolation of the results of the experiments at 50 °C, 20 °C and 60 °C to a temperature of 25 °C. It was found to be18.9 days.

 

At pH 4 less than 10 % of the reaction is observed after 5 days at 50 °C (t y2 at 25 °C > 1 year). Thus the test substance may be considered hydrolytically stable and according to Guideline 67/548/EEC Annex V no additional testing is required.

 

At pH 9 more than 50 % of the reaction is observed after 2.4 hours at 50 °C. Thus the test substance may be considered hydrolytically unstable and according to Guideline 67/548/EEC Annex V no additional testing is required.

Description of key information

At pH 7 the half-life period was determined by extrapolation of the results of the experiments at 50 °C, 20 °C and 60 °C to a temperature of 25 °C. It was found to be 18.9 days. At pH 4, a half-life can be estimated to > 1 year and at pH 9 < 1day at 25°C.

Key value for chemical safety assessment

Half-life for hydrolysis:
18.9 d
at the temperature of:
25 °C

Additional information

The objective of this study was the determination of the abiotic degradation of the test item, the determination of the hydrolysis rate as a function of the pH-value according to the consolidated version of Guideline 67/548/EEC Annex V (Council Directive 92/69/EEC) Part C: Methods for determination of ecotoxicity. C.7. abiotic degradation: hydrolysis as a function of pH and OECD test guidelines No. 111 (2004), Hydrolysis as a function of pH. Study performed in accordance with the Principles of Good Laboratory Practice (GLP) and reported with a GLP certificate.

At pH 7, the half-life period was determined by extrapolation of the results of the experiments at 50 °C, 20 °C and 60 °C to a temperature of 25 °C. It was found to be18.9 days.

At pH 4, less than 10 % of the reaction is observed after 5 days at 50 °C (t1/2at 25 °C > 1 year). Thus the test substance may be considered hydrolytically stable.

At pH 9, more than 50 % of the reaction is observed after 2.4 hours at 50 °C. Thus the test substance may be considered hydrolytically unstable.