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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:
2018-02-02 to 2018-03-29
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)
Version / remarks:
2004
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)
Version / remarks:
2008
Deviations:
no
GLP compliance:
yes (incl. certificate)
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
- Sampling intervals for the parent/transformation products:
Preliminary Test (Tier 1):
pH 4 at 50 °C: sampling at 0, 0.5, 1, 1.5, 2, 3, 3.5 and 4 h;
pH 7 at 50 °C: sampling at 0, 2, 3, 4, 4.5, 5, 5.5, 6 h;
pH 9 at 50 °C: sampling at 0, 1, 2, 2.5, 3, 3.5, 4, 4.5 h.
Main Test (Tier 2):
pH 4 at 20 °C: sampling at 0, 3, 24, 28, 48, 55, 72, 98 h;
pH 7 at 20 °C: sampling at 0, 3, 24, 48, 98, 146, 170, 191 h;
pH 9 at 20 °C: sampling at 0, 3, 24, 28, 48, 72, 98, 144 h;
pH 4 at 35 °C: sampling at 0, 1, 2, 3, 4, 5, 6, 7, 8 h;
pH 7 at 35 °C: sampling at 0, 3, 7, 24, 27, 29, 31, 47.5 h;
pH 9 at 35 °C: sampling at 0, 3, 7, 24, 28, 48, 55 h;
pH 4 at 50 °C: sampling at 0, 0.5, 1, 1.5, 2, 3, 3.5, 4 h;
pH 7 at 50 °C: sampling at 0, 2, 3, 4, 4.5, 5, 5.5, 6 h;
pH 9 at 50 °C: sampling at 0, 1, 2, 2.5, 3, 3.5, 4, 4.5 h;
- Sampling method: At each sampling time 2 mL diluent were added (dilution factor 2). The samples were homogenised by shaking after recrimbing. Two vials were prepared for each pH and each sampling date.
- Sampling intervals/times for pH measurements: same as sampling intervals for content determine
- Sample storage conditions before analysis: directly used for analysis
Buffers:
- Tested pH values: 4, 7, 9
- Type and final molarity of buffer: The citrate buffer (pH 4), the phosphate buffer (pH 7), and the borate buffer (pH 9) were prepared in a concentration of 0.05 M on the basis of the undissociated acids.
- Composition of buffer:
Citrate buffer pH 4 (0.05 M): Per 1 L ultra-pure water about 10.505 g citric acid monohydrate was weighed and about 60 mL of sodium hydroxide solution (1 M) was added to reach pH 4.
Phosphate buffer pH 7 (0.05 M): Per 1 L ultra-pure water about 6.805 g potassium dihydrogenphosphate was weighed and about 30 mL of sodium hydroxide solution (1 M) was added to reach pH 7.
Borate buffer pH 9 (0.05 M): Per 1 L ultra-pure water about 3.902 g boric acid and about 3.728 g potassium chloride were weighed and 21 mL of sodium hydroxide solution (1 M) were added to reach pH 9.
Details on test conditions:
TEST SYSTEM
- Type, material and volume of test flasks: 6 mL crimp vials
- Sterilisation method: Sterile buffer solutions used, sterilised by autoclaving
- Lighting: dark
- Measures taken to avoid photolytic effects: shaking in the dark
- Measures to exclude oxygen: degassing the buffers with argon for at least five minutes and purging the vessels with argon before preparing the test solution
- If no traps were used, is the test system closed/open: closed, with teflon sealed crimp caps

TEST PROCEDURE
- Test item preparation: At pH 4 and 9 about 100 mg and at pH 7 about 15 mg were given into a 100 mL volumetric flask. Afterwards the flask was brought to volume with the corresponding buffer solutions.
- Test concentration: 1000 mg/L at pH 4 and pH 9, 150 mg/L at pH 7
- Preliminary Test (Tier 1): performed at 50 ± 0.5 °C at three pH values 4, 7 and 9,
- Main Test (Tier 2): performed at pH 4, 7 and 9 at 20 °C, 35°C and 50°C
Duration:
4 h
pH:
4
Temp.:
50 °C
Initial conc. measured:
978.2 mg/L
Remarks:
Preliminary Test (Tier 1)
Duration:
6 h
pH:
7
Temp.:
50 °C
Initial conc. measured:
194.4 mg/L
Remarks:
Preliminary Test (Tier 1)
Duration:
4.5 h
pH:
9
Temp.:
50 °C
Initial conc. measured:
920.3 mg/L
Remarks:
Preliminary Test (Tier 1)
Duration:
98 h
pH:
4
Temp.:
20 °C
Initial conc. measured:
951.7 mg/L
Remarks:
Main Test (Tier 2)
Duration:
191 h
pH:
7
Temp.:
20 °C
Initial conc. measured:
102.2 mg/L
Remarks:
Main Test (Tier 2)
Duration:
144 h
pH:
9
Temp.:
20 °C
Initial conc. measured:
1 018.7 mg/L
Remarks:
Main Test (Tier 2)
Duration:
8 h
pH:
4
Temp.:
35 °C
Initial conc. measured:
1 014.8 mg/L
Remarks:
Main Test (Tier 2)
Duration:
47.5 h
pH:
7
Temp.:
35 °C
Initial conc. measured:
102.2 mg/L
Remarks:
Main Test (Tier 2)
Duration:
55 h
pH:
9
Temp.:
35 °C
Initial conc. measured:
1 018.7 mg/L
Remarks:
Main Test (Tier 2)
Duration:
4 h
pH:
4
Temp.:
50 °C
Initial conc. measured:
978.2 mg/L
Remarks:
Main Test (Tier 2)
Duration:
6 h
pH:
7
Temp.:
50 °C
Initial conc. measured:
194.4 mg/L
Remarks:
Main Test (Tier 2)
Duration:
4.5 h
pH:
9
Temp.:
50 °C
Initial conc. measured:
920.3 mg/L
Remarks:
Main Test (Tier 2)
Number of replicates:
2
Positive controls:
no
Negative controls:
no
Preliminary study:
More than 10 % of the test item were hydrolysed within 4 hours (for pH 4), respectively 6 hours (for pH 7) and 4.5 hours (for pH 9) at 50 °C. The Tier 2 test was performed for each pH value.
Transformation products:
not measured
pH:
4
Temp.:
20 °C
Hydrolysis rate constant:
-0.013 h-1
DT50:
22 h
Type:
(pseudo-)first order (= half-life)
Key result
pH:
7
Temp.:
20 °C
Hydrolysis rate constant:
-0.003 h-1
DT50:
94 h
Type:
(pseudo-)first order (= half-life)
pH:
9
Temp.:
20 °C
Hydrolysis rate constant:
-0.003 h-1
DT50:
105 h
Type:
(pseudo-)first order (= half-life)
pH:
4
Temp.:
35 °C
Hydrolysis rate constant:
-0.057 h-1
DT50:
5.1 h
Type:
(pseudo-)first order (= half-life)
pH:
7
Temp.:
35 °C
Hydrolysis rate constant:
-0.019 h-1
DT50:
18 h
Type:
(pseudo-)first order (= half-life)
pH:
9
Temp.:
35 °C
Hydrolysis rate constant:
-0.016 h-1
DT50:
18 h
Type:
(pseudo-)first order (= half-life)
pH:
4
Temp.:
50 °C
Hydrolysis rate constant:
-0.185 h-1
DT50:
1.5 h
Type:
(pseudo-)first order (= half-life)
pH:
7
Temp.:
50 °C
Hydrolysis rate constant:
-0.059 h-1
DT50:
5.4 h
Type:
(pseudo-)first order (= half-life)
pH:
9
Temp.:
50 °C
Hydrolysis rate constant:
-0.076 h-1
DT50:
4.1 h
Type:
(pseudo-)first order (= half-life)
Details on results:
TEST CONDITIONS
- pH, temperature maintained throughout the study: Yes

Main test Tier 2:

Time course of test item concentration at pH 4 at 20 °C:

Sampling time [h]

Concentration in 2 independent samples [mg/L]

Mean Concentration from 2 independent samples [mg/L]

Concentration in % of initial concentration [%]

log[c(t)/c(0)]

pH

0

956.0

951.7

100

0.00000

4.12

 

947.4

 

 

 

 

3

841.4

841.8

88

-0.05329

4.10

 

842.2

 

 

 

 

24

447.6

446.1

47

-0.32907

4.14

 

444.6

 

 

 

 

28

398.0

395.9

42

-0.38091

4.14

 

393.8

 

 

 

 

48

223.4

221.8

23

-0.63254

4.16

 

220.2

 

 

 

 

55

177.0

176.7

19

-0.73126

4.17

 

176.4

 

 

 

 

72

103.4

102.8

11

-0.96651

4.15

 

102.2

 

 

 

 

98

59.2

59.5

6

-1.20398

4.17

 

59.8

 

 

 

 

Time course of Test item concentration at pH 7 at 20 °C:

Sampling time [h]

Concentration in 2 independent samples [mg/L]

Mean Concentration from 2 independent samples [mg/L]

Concentration in % of initial concentration [%]

log[c(t)/c(0)]

pH

0

102.4

102.2

100

0.00000

7.10

 

102.0

 

 

 

 

3

100.0

100.2

98

-0.00858

7.05

 

100.4

 

 

 

 

24

87.6

87.7

86

-0.06645

7.04

 

87.8

 

 

 

 

48

75.2

75.0

73

-0.13439

7.05

 

74.8

 

 

 

 

98

61.4

61.3

60

-0.22199

7.05

 

61.2

 

 

 

 

146

35.0

35.1

34

-0.46414

7.05

 

35.2

 

 

 

 

170

26.6

26.5

26

-0.58621

7.06

 

26.4

 

 

 

 

191

21.8

21.8

21

-0.67099

7.05

 

21.8

 

 

 

 

Time course of Test item concentration at pH 9 at 20 °C:

Sampling time [h]

Concentration in 2 independent samples [mg/L]

Mean Concentration from 2 independent samples [mg/L]

Concentration in % of initial concentration [%]

log[c(t)/c(0)]

pH

0

1025.2

1018.7

100

0.00000

9.07

 

1012.2

 

 

 

 

3

1003.6

986.8

97

-0.01382

8.97

 

970.0

 

 

 

 

24

838.6

835.6

82

-0.08605

9.04

 

832.6

 

 

 

 

28

815.8

817.5

80

-0.0956

9.08

 

819.2

 

 

 

 

48

739.2

737.5

72

-0.1403

9.09

 

735.8

 

 

 

 

72

629.4

630.5

62

-0.2084

9.09

 

631.6

 

 

 

 

98

536.8

538.5

53

-0.2769

9.09

 

540.2

 

 

 

 

144

396.2

395.1

39

-0.4113

9.08

 

394.0

 

 

 

 

Time course of Test item concentration at pH 4 at 35 °C:

Sampling time [h]

Concentration in 2 independent samples [mg/L]

Mean Concentration from 2 independent samples [mg/L]

Concentration in % of initial concentration [%]

log[c(t)/c(0)]

pH

0

1017.0

1014.8

100

0.0000

4.10

 

1012.6

 

 

 

 

1

863.2

861.9

85

-0.07092

4.07

 

860.6

 

 

 

 

2

740.6

743.4

73

-0.13516

4.09

 

746.2

 

 

 

 

3

662.6

660.3

65

-0.18664

4.09

 

658.0

 

 

 

 

4

587.2

587.2

58

-0.23759

4.09

 

587.2

 

 

 

 

5

513.4

508.7

50

-0.29992

4.09

 

506.4

 

 

 

 

6

451.6

449

44

-0.35413

4.12

 

449.6

 

 

 

 

7

390.6

393.4

39

-0.41155

4.12

 

401.0

 

 

 

 

8

353.0

351.1

35

-0.46095

4.14

 

352.4

 

 

 

 

Time course of Test item concentration at pH 7 at 35 °C:

Sampling time [h]

Concentration in 2 independent samples [mg/L]

Mean Concentration from 2 independent samples [mg/L]

Concentration in % of initial concentration [%]

log[c(t)/c(0)]

pH

0

102.4

102.2

100

0.0000

7.10

 

102.0

 

 

 

 

3

95.4

95.4

93

-0.0299

7.05

 

95.4

 

 

 

 

7

87.0

86.7

85

-0.0714

7.07

 

86.4

 

 

 

 

24

41.8

41.7

41

-0.3893

7.03

 

41.6

 

 

 

 

27

35.6

35.9

35

-0.4544

7.05

 

36.2

 

 

 

 

29

33.0

32.8

32

-0.4936

7.04

 

32.6

 

 

 

 

31

30.0

29.9

29

-0.5338

7.03

 

29.8

 

 

 

 

47.5

13.2

13.2

13

-0.8889

7.04

 

13.2

 

 

 

 

Time course of Test item concentration at pH 9 at 35 °C:

Sampling time [h]

Concentration in 2 independent samples [mg/L]

Mean Concentration from 2 independent samples [mg/L]

Concentration in % of initial concentration [%]

log[c(t)/c(0)]

pH

0

1025.2

1018.7

100

0.00000

9.07

 

1012.2

 

 

 

 

3

904.8

906.0

89

-0.05092

9.02

 

907.2

 

 

 

 

7

777.8

773.2

76

-0.11975

9.03

 

768.6

 

 

 

 

24

409.0

409.8

40

-0.39547

9.03

 

410.6

 

 

 

 

28

350.6

349.6

34

-0.4645

9.05

 

348.6

 

 

 

 

48

160.8

161.9

16

-0.7988

9.02

 

163.0

 

 

 

 

55

128.2

128.2

13

-0.9002

9.03

 

128.2

 

 

 

 

Time course of Test item concentration at pH 4 at 50 °C:

Sampling time [h]

Concentration in 2 independent samples [mg/L]

Mean Concentration from 2 independent samples [mg/L]

Concentration in % of initial concentration [%]

log[c(t)/c(0)]

pH

0

984.6

978.2

100

0.0000

4.14

 

971.8

 

 

 

 

0.5

743.6

746.6

76

-0.1173

4.10

 

749.6

 

 

 

 

1

595.8

593.6

61

-0.2169

4.16

 

591.4

 

 

 

 

1.5

476.2

477.6

49

-0.3114

4.13

 

479.0

 

 

 

 

2

377.4

376.5

38

-0.4147

4.14

 

375.6

 

 

 

 

3

261.4

261.5

27

-0.5730

4.18

 

261.6

 

 

 

 

3.5

211.2

211.9

22

-0.6643

4.16

 

212.6

 

 

 

 

4

172.2

172.3

18

-0.7541

4.15

 

172.4

 

 

 

 

Time course of Test item concentration at pH 7 at 50 °C:

Sampling time [h]

Concentration in 2 independent samples [mg/L]

Mean Concentration from 2 independent samples [mg/L]

Concentration in % of initial concentration [%]

log[c(t)/c(0)]

pH

0

194.0

194.4

100

0.0000

7.13

 

194.8

 

 

 

 

2

157.8

157.7

81

-0.0909

7.13

 

157.6

 

 

 

 

3

136.4

136.4

70

-0.1539

7.13

 

136.4

 

 

 

 

4

118.2

118.2

61

-0.2161

7.14

 

118.2

 

 

 

 

4.5

109.4

109.4

56

-0.2497

7.14

 

109.4

 

 

 

 

5

102.2

102.2

53

-0.2792

7.13

 

102.2

 

 

 

 

5.5

94.0

94.1

48

-0.3151

7.13

 

94.2

 

 

 

 

6

88.2

88.3

45

-0.3427

7.14

 

88.4

 

 

 

 

Time course of Test item concentration at pH 9 at 50 °C:

Sampling time [h]

Concentration in 2 independent samples [mg/L]

Mean Concentration from 2 independent samples [mg/L]

Concentration in % of initial concentration [%]

log[c(t)/c(0)]

pH

0

920.2

920.3

100

0.0000

9.07

 

920.4

 

 

 

 

1

800.2

799.3

87

-0.0612

8.97

 

798.4

 

 

 

 

2

672.4

669.4

73

-0.1382

8.94

 

666.4

 

 

 

 

2.5

610.4

610.0

66

-0.1786

8.95

 

609.6

 

 

 

 

3

560.4

556.3

60

-0.2186

8.98

 

552.2

 

 

 

 

3.5

515.4

515.3

56

-0.2519

8.95

 

515.2

 

 

 

 

4

463.4

462.6

50

-0.2987

8.92

 

461.8

 

 

 

 

4.5

416.4

419.0

46

-0.3417

8.97

 

421.6

 

 

 

Validity criteria fulfilled:
yes
Conclusions:
The determined degradation half-life values are 22, 94, 105 h at 20°C for pH 4, 7, 9; 5.1, 18, 18 h at 35°C for pH 4, 7, 9; 1.5, 5.4, 4.1 h at 50°C for pH 4, 7, 9, respectively.
Executive summary:

The abiotic degradation of test item as a function of pH in aqueous solution was determined according to OECD guideline 111 and EC method C.7 (440/2008). 

A preliminary test was performed at 50 ± 0.5 °C at three pH values 4, 7 and 9. A sufficient number of measurements were made, in order to be able to estimate whether for each pH value and at 50 °C, less than 10 % of hydrolysis is observed after 120 hours or not. The hydrolysis of test item was more than 10 % at pH 4, 7 and 9 at 50 °C over a period of 2 hours.

The main test (Tier 2) was performed at pH 4, 7 and 9. The buffered solution of the test substance was tempered at 20 °C ± 0.5 °C, 35 °C ± 0.5 °C and 50 °C ± 0.5 °C. To test for first-order behaviour, each reaction solution was analysed in time intervals which provide at least six spaced data points normally between 10 % and 90 % hydrolysis of the substance.

The determined degradation half-life values are 22, 94, 105 h at 20°C for pH 4, 7, 9; 5.1, 18, 18 h at 35°C for pH 4, 7, 9; 1.5, 5.4, 4.1 h at 50°C for pH 4, 7, 9, respectively.

Description of key information

For this endpoint one test is available, in which theabiotic degradation of test item as a function of pH in aqueous solution was determined according to OECD guideline 111 and EC method C.7 (440/2008). 

The main test (Tier 2) was performed at pH 4, 7 and 9. The buffered solution of the test substance was tempered at 20 °C ± 0.5 °C, 35 °C ± 0.5 °C and 50 °C ± 0.5 °C. The determined degradation half-life values are 22, 94, 105 h at 20°C for pH 4, 7, 9; 5.1, 18, 18 h at 35°C for pH 4, 7, 9; 1.5, 5.4, 4.1 h at 50°C for pH 4, 7, 9, respectively.

The reported key value is the half-life at 20°C and at pH 7.

Key value for chemical safety assessment

Half-life for hydrolysis:
94 h
at the temperature of:
20 °C

Additional information

For this endpoint one test is available, in which theabiotic degradation of test item as a function of pH in aqueous solution was determined according to OECD guideline 111 and EC method C.7 (440/2008). 

A preliminary test was performed at 50 ± 0.5 °C at three pH values 4, 7 and 9. A sufficient number of measurements were made, in order to be able to estimate whether for each pH value and at 50 °C, less than 10 % of hydrolysis is observed after 120 hours or not. The hydrolysis of test item was more than 10 % at pH 4, 7 and 9 at 50 °C over a period of 2 hours.

The main test (Tier 2) was performed at pH 4, 7 and 9. The buffered solution of the test substance was tempered at 20 °C ± 0.5 °C, 35 °C ± 0.5 °C and 50 °C ± 0.5 °C. To test for first-order behaviour, each reaction solution was analysed in time intervals which provide at least six spaced data points normally between 10 % and 90 % hydrolysis of the substance.

The determined degradation half-life values are 22, 94, 105 h at 20°C for pH 4, 7, 9; 5.1, 18, 18 h at 35°C for pH 4, 7, 9; 1.5, 5.4, 4.1 h at 50°C for pH 4, 7, 9, respectively.