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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
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
Qualifier:
according to
Guideline:
EPA OPPTS 835.2120 (Hydrolysis of Parent and Degradates as a Function of pH at 25°C)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Specific details on test material used for the study:
Appearance: Colourless liquid
Batch: ZMG-197685
Purity/Composition: See Certificate of Analysis
Test item storage: At room temperature container flushed with nitrogen
Stable under storage conditions until: 29 December 2018 (expiry date)
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
Prelimniary test: For each sampling time, duplicate sterile glass vessels of 20 mL were filled under nitrogen for approximately ¾ with test solution and placed in the dark in a temperature controlled environment at 50.2°C +- 0.1°C.
The concentration of the test item in the test samples was determined immediately after preparation (t=0) and after 5 days. The samples taken at t=5 days were cooled to room temperature using running tap water.
Analysis was performed on subsamples of 9 mL. The samples were extracted in a 3:1 (v:v) ratio with ethylacetate and analyzed.
Blank buffer solutions containing a similar content of blank spiking solution were treated similarly as the test samples and analyzed at t=0.
The pH of each of the test solutions (except for the blanks) was determined at each sampling time.
Mian test: Test samples were prepared and treated similarly as during the preliminary test. The concentrations of the test item were determined immediately after preparation (t=0) and at several sampling points after t=0.
The samples not analyzed on the sampling day were stored in the freezer. Storage stability under these conditions was determined by the analysis of additional quality control (QC) samples prepared at half the nominal concentration of the test samples. On the day of analysis, the frozen samples were defrosted at room temperature, treated and analyzed. The stored samples were found to be stable if the mean accuracy was in the range 70-110%. Based on the results obtained the samples of pH 7 were stable when stored in the freezer for 15 days. The samples of pH 9 were found to be not stable when stored in the freezer for 4 days, i.e. mean accuracy of 61% (results are archived in the raw data). Therefore, a QC correction was applied for the results of pH 9 samples that were stored in the freezer. Since the result of hydrolysis (intercept and slope) did not change significantly when corrected values were used, the results were only used as confirmation while the uncorrected values were used for the calculation of the degree of hydrolysis.
Blank buffer solutions were treated similarly as the test samples and analyzed at t=0.
The pH of each of the test solutions (except for the blanks) was determined at least at the beginning and at the end of the test.
Buffers:
Acetate buffer pH 4, 0.01 M Solution of 16.7% 0.01 M sodium acetate in water and 83.3% 0.01 M acetic acid in water. Buffer contained 0.0009% (w/v) sodium azide.
Phosphate buffer pH 7, 0.01 M Solution of 0.01 M potassium di-hydrogen-phosphate in water adjusted to pH 7 using 1N sodium hydroxide. Buffer contained 0.0009% (w/v) sodium azide.
Borate buffer pH 9, 0.01 M Solution of 0.01 M boric acid in water and 0.01 M potassium chloride in water adjusted to pH 9 using 1N sodium hydroxide. Buffer contained 0.0009% (w/v) sodium azide.
Details on test conditions:
8.3.1. Preliminary Test - Tier 1
The buffer solutions were filter-sterilised through a 0.2 µm FP 30/0.2 CA-S filter (Whatman, Dassel, Germany) and transferred into a sterile vessel. To exclude oxygen, nitrogen gas was purged through the solution for 5 minutes. The test item was spiked to the solutions at a target concentration of 5 mg/L using a spiking solution in acetone. For each sampling time, duplicate sterile glass vessels of 20 mL were filled under nitrogen for approximately ¾ with test solution and placed in the dark in a temperature controlled environment at 50.2°C  0.1°C.
The spiking volume was < 1% of the sample volume. Nominal concentrations were not corrected for the spiking volume.
The concentration of the test item in the test samples was determined immediately after preparation (t=0) and after 5 days. The samples taken at t=5 days were cooled to room temperature using running tap water.
Analysis was performed on subsamples of 9 mL. The samples were extracted in a 3:1 (v:v) ratio with ethylacetate and analyzed.
Blank buffer solutions containing a similar content of blank spiking solution were treated similarly as the test samples and analyzed at t=0.
The pH of each of the test solutions (except for the blanks) was determined at each sampling time.
8.3.2. Main Study - Tier 2
Test samples were prepared and treated similarly as during the preliminary test. The concentrations of the test item were determined immediately after preparation (t=0) and at several sampling points after t=0.
The samples not analyzed on the sampling day were stored in the freezer. Storage stability under these conditions was determined by the analysis of additional quality control (QC) samples prepared at half the nominal concentration of the test samples. On the day of analysis, the frozen samples were defrosted at room temperature, treated and analyzed. The stored samples were found to be stable if the mean accuracy was in the range 70-110%. Based on the results obtained the samples of pH 7 were stable when stored in the freezer for 15 days. The samples of pH 9 were found to be not stable when stored in the freezer for 4 days, i.e. mean accuracy of 61% (results are archived in the raw data). Therefore, a QC correction was applied for the results of pH 9 samples that were stored in the freezer. Since the result of hydrolysis (intercept and slope) did not change significantly when corrected values were used, the results were only used as confirmation while the uncorrected values were used for the calculation of the degree of hydrolysis.
Blank buffer solutions were treated similarly as the test samples and analyzed at t=0.
The pH of each of the test solutions (except for the blanks) was determined at least at the beginning and at the end of the test.

Duration:
5 d
pH:
4
Temp.:
50.2 °C
Initial conc. measured:
ca. 5 mg/L
Remarks:
preliminary tier 1
Duration:
5 d
pH:
7
Temp.:
50.2 °C
Initial conc. measured:
ca. 5 mg/L
Remarks:
preiminary-tier 1
Duration:
5 d
pH:
9
Temp.:
50.2 °C
Initial conc. measured:
ca. 5 mg/L
Remarks:
preliminary - tier 1
Duration:
746 h
pH:
7
Temp.:
20 °C
Initial conc. measured:
ca. 5 mg/L
Duration:
311 h
pH:
7
Temp.:
40 °C
Initial conc. measured:
ca. 5 mg/L
Duration:
143 h
pH:
7
Temp.:
50 °C
Initial conc. measured:
ca. 5 mg/L
Duration:
98 h
pH:
9
Temp.:
20 °C
Initial conc. measured:
ca. 5 mg/L
Duration:
4 h
pH:
9
Temp.:
40 °C
Initial conc. measured:
ca. 5 mg/L
Duration:
1 h
pH:
9
Temp.:
50 °C
Initial conc. measured:
ca. 5 mg/L
Number of replicates:
duplicates
Positive controls:
no
Negative controls:
yes
Statistical methods:
Linear regression analysis on the logarithm of the relative concentration between 10% and 90% of hydrolysis and time will be performed to investigate the pseudo-first order behavior of the test item.
If the test item shows a pseudo-first order behavior, the half-life times (t0.5) of the test item will be determined according to the model for pseudo-first order reactions. Linear regression analysis on the logarithm of all relative concentrations and time will be performed. The rate constants kobs and half-life time at each test temperature and at 25°C will be determined from the relationships and the Arrhenius equation.
Preliminary study:
At pH 7 and pH 9, a degree of hydrolysis of ≥ 10% was observed after 5 days. According to the guideline, the higher Tier test was required to determine the half-life time of the test item.
A degree of hydrolysis of < 10% was observed at pH 4 after 5 days. It demonstrated that the half-life time of the test item at 25°C is > 1 year. According to the guideline, no further tests were required.
No test item was detected in the blank buffer solutions.
The mean recoveries of the of the test item containing buffer solutions at t=0 fell within the criterion range of 90-110%. It demonstrated that the analytical method was adequate to support the hydrolysis study on the test item.
Test performance:
No test item was detected in the blank buffer solutions.
The mean recoveries of the test item containing buffer solutions at t=0 fell within the criterion range of 90-110% for 20°C and 50°C. The mean recovery for 40°C fell slightly out of range (i.e. 85%). Since the degree of hydrolysis was calculated relative to initial, this had no impact on the results. It demonstrated that the analytical method was adequate to support the hydrolysis study on the test item.
Transformation products:
not measured
pH:
4
Temp.:
50.2 °C
Duration:
ca. 0 h
Remarks on result:
hydrolytically stable based on preliminary test
% Recovery:
ca. 99
pH:
7
Temp.:
50.2 °C
Duration:
ca. 0 h
% Recovery:
ca. 98
pH:
9
Temp.:
50.2 °C
Duration:
ca. 0 h
% Recovery:
> 100
pH:
7
Temp.:
20 °C
Duration:
ca. 0 h
% Recovery:
ca. 85
pH:
7
Temp.:
40 °C
Duration:
ca. 0 h
% Recovery:
ca. 95
pH:
7
Temp.:
50 °C
Duration:
ca. 0 h
% Recovery:
ca. 94
pH:
9
Temp.:
20 °C
Duration:
ca. 0 h
% Recovery:
> 100
pH:
9
Temp.:
40 °C
Duration:
ca. 0 h
% Recovery:
ca. 92
pH:
9
Temp.:
50 °C
Duration:
ca. 0 h
pH:
4
Temp.:
25 °C
DT50:
> 1 yr
Type:
other: result from tier 1 assessment
Remarks on result:
hydrolytically stable based on preliminary test
Key result
pH:
7
Temp.:
20 °C
Hydrolysis rate constant:
ca. 0 h-1
DT50:
ca. 102 d
Type:
(pseudo-)first order (= half-life)
pH:
7
Temp.:
25 °C
Hydrolysis rate constant:
ca. 0.001 h-1
DT50:
ca. 43 d
Type:
(pseudo-)first order (= half-life)
pH:
7
Temp.:
40 °C
Hydrolysis rate constant:
ca. 0.008 h-1
DT50:
ca. 3.7 d
Type:
(pseudo-)first order (= half-life)
pH:
7
Temp.:
50 °C
Hydrolysis rate constant:
ca. 0.047 h-1
DT50:
ca. 15 h
Type:
(pseudo-)first order (= half-life)
pH:
9
Temp.:
20 °C
Hydrolysis rate constant:
ca. 0.029 h-1
DT50:
ca. 24 h
Type:
(pseudo-)first order (= half-life)
pH:
9
Temp.:
25 °C
Hydrolysis rate constant:
ca. 0.064 h-1
DT50:
ca. 11 h
Type:
(pseudo-)first order (= half-life)
pH:
9
Temp.:
40 °C
Hydrolysis rate constant:
ca. 0.597 h-1
DT50:
ca. 1.2 h
Type:
(pseudo-)first order (= half-life)
pH:
9
Temp.:
50 °C
Hydrolysis rate constant:
ca. 2.62 h-1
DT50:
ca. 0.26 h
Type:
(pseudo-)first order (= half-life)
Details on results:
TEST CONDITIONS
- pH, sterility, temperature, and other experimental conditions maintained throughout the study: Yes
- Anomalies or problems encountered (if yes): none

MAJOR TRANSFORMATION PRODUCTS
Not determined

MINERALISATION (distinguish between dark and irradiated samples)
Not determined

INDICATION OF UNSTABLE TRANSFORMATION PRODUCTS:
Not determined

VOLATILIZATION (at end of study)
Not determined

UNIDENTIFIED RADIOACTIVITY (at end of study)
Not applicable

PATHWAYS OF HYDROLYSIS
Not determined
Results with reference substance:
No reference substance

Preliminary Test: Hydrolysis of the Test Item at pH 4, pH 7 and pH 9

pH code

Sampling time

Analyzed concentration
[mg/L]

Degree of hydrolysis
[%]

pH

Individual

Mean

pH 4

0 hours

5.42

 

 

4.0

 

 

5.34

 

 

4.0

 

5 days

5.16

4.2

4.0

4.1

 

 

5.17

3.8

 

4.1

pH 7

0 hours

4.90

 

 

7.0

 

 

4.99

 

 

7.0

 

5 days

0.0161

10

10

7.1

 

 

0.00561

11

 

7.1

pH 9

0 hours

4.94

 

 

9.0

 

 

4.88

 

 

9.0

 

5 days

n.d.

n.a.

n.a.

9.0

 

 

n.d.

n.a.

 

9.0

1Estimated value, calculated by extrapolation of the calibration curve.

n.d.        not detected

n.a.        not applicable

Main Test pH 7: Hydrolysis of the Test Item at 20°C

Sampling time


[hours]

Analyzed concentration [mg/L]

Relative concentration
[%]

Logarithm relative
concentration

pH

0.00

6.231

129

2.11

7.0

0.00

4.82

100

2.00

7.0

0.00

6.942

126

2.10

7.0

0.00

4.962

90

1.95

7.0

22.68

4.83

100

2.00

7.0

22.68

4.74

98

1.99

7.0

72.12

4.90

102

2.01

7.0

72.12

4.95

103

2.01

7.0

169.85

4.34

90

1.95

6.9

169.85

4.35

90

1.96

6.9

217.90

4.63

96

1.98

6.9

217.90

4.56

95

1.98

6.9

361.27

5.47

113

2.05

6.9

361.27

5.31

110

2.04

6.9

385.68

4.39

91

1.96

7.0

385.68

4.32

90

1.95

7.0

481.10

4.56

95

1.98

7.0

481.10

4.74

98

1.99

7.0

654.82

4.18

87

1.94

7.0

654.82

4.48

93

1.97

7.0

678.07

3.93

82

1.91

7.0

678.07

3.94

82

1.91

7.0

698.30

4.14

86

1.93

7.0

698.30

4.02

83

1.92

7.0

702.00

4.18

87

1.94

7.0

702.00

4.28

89

1.95

7.0

723.88

4.04

84

1.92

7.0

723.88

4.02

83

1.92

7.0

745.83

4.04

84

1.92

7.0

745.83

4.17

87

1.94

7.0

1Result of this sample was not used for calculation of degree of hydrolysis since this result was out of line and would give a not representative outcome.

2The samples of t=0 were reinjected in order to confirm the result of the first injections and they were not used for calculation.

Main Test pH 7: Hydrolysis of the Test Item at 40°C

Sampling time


[hours]

Analyzed concentration [mg/L]

Relative concentration
[%]

Logarithm relative
concentration

pH

0.00

4.23

99

2.00

7.0

0.00

4.31

101

2.00

7.0

24.28

4.49

105

2.02

7.0

24.28

4.38

102

2.01

7.0

47.97

2.97

70

1.84

7.0

47.97

2.95

69

1.84

7.0

69.60

2.44

57

1.76

7.1

69.60

2.62

61

1.79

7.1

70.42

2.49

58

1.77

7.1

70.42

2.39

56

1.75

7.1

71.43

2.57

60

1.78

7.1

71.43

2.41

56

1.75

7.1

72.42

2.53

59

1.77

7.1

72.42

3.26

76

1.88

7.1

73.92

2.47

58

1.76

7.1

73.92

2.44

57

1.76

7.1

143.25

1.36

32

1.50

7.1

143.25

1.42

33

1.52

7.1

165.73

1.15

27

1.43

7.1

165.73

1.21

28

1.45

7.1

194.27

0.90

21

1.32

7.1

194.27

0.92

21

1.33

7.1

311.07

0.46

11

1.03

7.1

311.07

0.43

10

1.00

7.1

 

      
Main Test pH 7: Hydrolysis of the Test Item at 50°C

Sampling time


[hours]

Analyzed concentration [mg/L]

Relative concentration
[%]

Logarithm relative
concentration

pH

0.00

4.98

105

2.02

7.0

0.00

4.47

95

1.98

7.0

2.07

3.97

84

1.92

7.0

2.07

4.08

86

1.94

7.0

4.00

3.49

74

1.87

7.0

4.00

3.73

79

1.90

7.0

4.57

3.62

77

1.88

7.0

4.57

3.51

74

1.87

7.0

5.40

3.50

74

1.87

7.1

5.40

3.50

74

1.87

7.1

25.00

1.92

41

1.61

7.0

25.00

1.86

39

1.60

7.0

27.28

1.54

33

1.51

7.0

27.28

1.65

35

1.54

7.0

49.33

0.500

11

1.02

7.0

49.33

0.525

11

1.05

7.0

143.63

0.00271

0.057

-1.24

7.1

143.63

0.010 1

0.22

-0.66

7.1

1Estimated value, calculated by extrapolation of the calibration curve.


Main Test pH 9: Hydrolysis of the Test Item at 20°C

Sampling time


[hours]

Analyzed concentration [mg/L]

Relative concentration
[%]

Logarithm relative
concentration

pH

0.00

5.25

111

2.05

9.0

0.00

4.17

89

1.95

9.0

0.82

4.97

106

2.02

9.0

0.82

4.39

93

1.97

9.0

1.38

4.04

86

1.93

9.0

1.38

4.35

92

1.97

9.0

2.38

4.64

99

1.99

9.0

2.38

4.66

99

2.00

9.0

5.92

3.56

76

1.88

9.0

5.92

3.58

76

1.88

9.0

24.42

2.28

48

1.68

9.1

24.42

2.24

48

1.68

9.1

24.88

2.07

44

1.64

9.1

24.88

2.10

45

1.65

9.1

25.35

1.48

31

1.50

9.1

25.35

2.13

45

1.66

9.1

26.37

2.11

45

1.65

9.1

26.37

2.14

46

1.66

9.1

27.35

1.99

42

1.63

9.0

27.35

1.26

27

1.43

9.1

28.85

1.26

27

1.43

9.1

28.85

1.83

39

1.59

9.1

98.25

0.28

6.0

0.78

9.0

98.25

0.31

6.6

0.82

9.0


Main Test at pH 9: Hydrolysis of the Test Item at 40°C

Sampling time


[hours]

Analyzed concentration [mg/L]

Relative concentration
[%]

Logarithm relative
concentration

pH

0.00

5.18

101

2.01

9.0

0.00

5.03

99

1.99

9.0

0.72

3.39

66

1.82

9.1

0.72

3.24

64

1.80

9.0

1.55

1.94

38

1.58

9.1

1.55

1.95

38

1.58

9.1

2.15

1.42

28

1.44

9.0

2.15

1.28

25

1.40

9.1

2.27

1.17

23

1.36

9.0

2.27

1.13

22

1.35

9.1

2.43

1.18

23

1.36

9.1

2.43

1.02

20

1.30

9.1

2.60

1.06

21

1.32

9.1

2.60

0.993

19

1.29

9.1

4.03

0.512

10

1.00

9.1

4.03

0.456

8.9

0.95

9.1

 


 

Table 11        
Main Test at pH 9: Hydrolysis of the Test Item at 50°C

Sampling time


[hours]

Analyzed concentration [mg/L]

Relative concentration
[%]

Logarithm relative
concentration

pH

0.00

4.57

99

2.00

9.0

0.00

4.63

101

2.00

9.0

0.17

2.99

65

1.81

9.0

0.17

2.78

60

1.78

9.0

0.25

2.24

49

1.69

9.0

0.25

2.37

51

1.71

9.0

0.33

1.79

39

1.59

9.0

0.42

1.63

36

1.55

9.0

0.42

1.59

35

1.54

9.0

0.53

1.02

22

1.35

9.0

0.53

1.19

26

1.41

9.0

0.62

0.820

18

1.25

9.0

0.62

0.803

17

1.24

9.0

0.72

0.588

13

1.11

9.0

0.72

0.584

13

1.10

9.0

0.87

0.440

10

0.98

9.0

0.87

0.498

11

1.03

9.0

1.03

0.319

6.9

0.84

9.0

1.03

0.340

7.4

0.87

9.0

 


Validity criteria fulfilled:
yes
Conclusions:
The preliminary test (Tier 1) and main study (Tier 2) were performed for the determination of the rate of hydrolysis of 1,3-dichloro-2-propanol at pH values normally found in the environment (pH 4-9).
At pH 4 a degree of hydrolysis of < 10% was observed after 5 days. According to the guideline, performance of the main study (Tier 2) was not required.
The half-lives of the substance under the variable environmental conditions are as follows- 20 celsius: pH 7 102 days, pH 9 24 hours; 25 celsius: pH 4 > 1year, pH 7 43 days, pH 9 11 hours; 40 celsius: pH 7 3.7 days, pH 9 1.2 hours; 50 celsius: pH 7 15 hours, pH 9 0.26 hours.

Description of key information

The preliminary test (Tier 1) and main study (Tier 2) were performed for the determination of the rate of hydrolysis of 1,3-dichloro-2-propanol at pH values normally found in the environment (pH 4-9).

At pH 4 a degree of hydrolysis of < 10% was observed after 5 days.  According to the guideline, performance of the main study (Tier 2) was not required.

The half-lives of the substance under the variable environmental conditions are as follows- 20 celsius: pH 7 102 days, pH 9 24 hours; 25 celsius: pH 4 > 1year, pH 7 43 days, pH 9 11 hours; 40 celsius: pH 7 3.7 days, pH 9 1.2 hours; 50 celsius: pH 7 15 hours, pH 9 0.26 hours.

Key value for chemical safety assessment

Half-life for hydrolysis:
102 d
at the temperature of:
20 °C

Additional information