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Environmental fate & pathways

Hydrolysis

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Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
from 2018-09-05 to 2019-01-22
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
GLP compliance:
yes (incl. certificate)
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
At each analytical occasion two vials of the test solution were removed from the thermostat and analysed. Samples were 200-fold, 250-fold, or 500-fold diluted with ultra-pure water and then samples were analysed by LC/MS/MS method.
Buffers:
- pH: 7
- Composition of buffer:
pH 7.0: 296 mL 0.2 M Sodium hydroxide and 500 mL 0.2 M Potassium dihydrogen phosphate were diluted to 2000 mL with ultra-pure water. In order to exclude oxygen, nitrogen was bubbled into the water for five minutes before preparation of the solution. Different amounts were prepared keeping this ratio.
Details on test conditions:
TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: glass beakers
- Sterilisation method: using hot air steriliser
- Lighting: no
- Measures taken to avoid photolytic effects: The test was carried out using a dark thermostat to avoid photolytic effects.
- Measures to exclude oxygen: Nitrogen was bubbled into the water for five minutes before preparation of the solution.

TEST MEDIUM
- Kind and purity of water: ultrapure, sterile
- Preparation of test medium: Buffer solutions were preapred using reagent grade chemicals and ultrapure, sterile water.
- Renewal of test solution: not performed

OTHER TEST CONDITIONS
- Adjustment of pH: no
Duration:
30 d
pH:
7
Temp.:
12 °C
Initial conc. measured:
987 mg/L
Duration:
30 d
pH:
7
Temp.:
25 °C
Initial conc. measured:
975 mg/L
Duration:
30 d
pH:
7
Temp.:
50 °C
Initial conc. measured:
948 mg/L
Duration:
12 d
pH:
7
Temp.:
60 °C
Initial conc. measured:
2 140 mg/L
Duration:
7 d
pH:
7
Temp.:
70 °C
Initial conc. measured:
2 205 mg/L
Duration:
6 d
pH:
7
Temp.:
80 °C
Initial conc. measured:
2 197 mg/L
Number of replicates:
2
Positive controls:
no
Negative controls:
yes
Remarks:
buffer control
Preliminary study:
In a preliminary test was determined that the test item is not stable at pH 7 and 50 °C. Therefore, this main test was perfomed.
Transformation products:
yes
Key result
pH:
7
Temp.:
12 °C
Hydrolysis rate constant:
0 h-1
Type:
(pseudo-)first order (= half-life)
pH:
7
Temp.:
25 °C
Hydrolysis rate constant:
0 h-1
Type:
(pseudo-)first order (= half-life)
pH:
7
Temp.:
50 °C
Hydrolysis rate constant:
0.001 h-1
DT50:
654 h
Type:
(pseudo-)first order (= half-life)
pH:
7
Temp.:
60 °C
Hydrolysis rate constant:
0.002 h-1
DT50:
322 h
Type:
(pseudo-)first order (= half-life)
pH:
7
Temp.:
70 °C
Hydrolysis rate constant:
0.004 h-1
DT50:
165 h
Type:
(pseudo-)first order (= half-life)
pH:
7
Temp.:
80 °C
Hydrolysis rate constant:
0.005 h-1
DT50:
151 h
Type:
(pseudo-)first order (= half-life)
Other kinetic parameters:
Second-order kinetics
Temperature Slope kobs, L/g·h t1/2 Regression Coefficient
50 °C 0.00153 0.00153 644 h 0.81
60 °C 0.00154 0.00154 303 h 0.73
70 °C 0.00305 0.00305 149 h 0.75
80 °C 0.00359 0.00359 127 h 0.72
Details on results:
Hydrolysis could not be observed at 12 °C and 25 °C after 30 days.

Sterility confirmation test

At the end of the experiments samples of the test solutions originated from 12 °C, 25 °C and 50 °C were submitted for sterility confirmation. Samples were investigated by plating experiment on Columbia blood agar plates. These agar plates were incubated at 37 °C, for 24 hours, thereafter at 20 °C for further 24 hours, at the end evaluated. No microbial growth was obtained, the plates remained clear.

Results

Table 1. Measured data at pH 7

Temperature

Sampling time (days)

Concentration
(mg/L)
n=2

Hydrolysis
(%)

Measured pH

TMD content*

12 °C

Control buffer

-

-

7.00

-

Start

987 (n=3)

-

7.13

7 %

0.8

957

3

7.12

-

1.8

1017

-3

7.15

-

2.8

986

0

7.12

-

3.8

1011

-2

7.13

-

6.8

980

1

7.11

-

9.8

1037

-5

7.16

-

15.8

851

14

7.14

-

29.8

1049

-6

7.13

8 %

25 °C

Control buffer

-

-

7.00

-

Start

975 (n=3)

-

7.13

7 %

0.8

923

5

7.13

-

1.8

995

-2

7.13

-

2.8

942

3

7.14

-

3.8

986

-1

7.12

-

6.8

919

6

7.12

-

9.8

975

0

7.12

-

15.8

858

12

7.14

-

29.8

951

2

7.12

9 %

50 °C

Control buffer

-

-

7.00

-

Start

990 (n=3)

-

7.13

7 %

0.8

948

4

7.11

-

1.8

911

8

7.12

-

2.8

834

16

7.14

-

3.8

807

19

7.12

-

6.8

670

32

7.11

18 %

9.8

649

34

7.12

-

15.8

486

51

7.16

-

29.8

504

49

7.11

31 %

60 °C

Control buffer

-

-

7.05

-

Start

2140 (n=3)

-

7.09

7 %

0.8

1743

19

7.13

 

1.8

1430

33

7.11

 

2.8

1279

40

7.14

 

4.1

1127

47

7.11

 

5.8

1143

47

7.18

 

7.7

1152

46

7.18

 

11.8

1041

51

7.14

23 %

70 °C

Control buffer

-

-

7.01

-

Start

2205 (n=3)

-

7.10

6 %

0.8

1589

28

7.13

-

1.8

1218

45

7.09

-

2.1

1232

44

7.11

-

2.7

1163

47

7.12

-

3.1

1144

48

7.11

-

3.8

1058

52

7.12

-

6.8

1003

55

7.10

23 %

80 °C

Control buffer

-

-

7.02

-

Start

2197 (n=3)

-

7.13

7 %

0.3

1523

31

7.15

-

1

1196

46

7.16

-

1.3

1212

45

7.13

-

1.8

1179

46

7.13

-

2.3

1121

49

7.11

-

3

989

55

7.10

-

6

931

58

7.11

25 %

* Trimethyl-1,6-hexanediamine (TMD) content was calculated on the basis of the chromatographic peak areas. TMD peak was excluded from the calculation of the hydrolysis rate.

Test item did not decompose at 12 °C and at 25 °C after 30 days incubation. Decomposition up to 58 % was observed at temperatures above 50 °C.

Based on the results obtained, test substance cannot be considered as hydrolytically unstable at pH 7. Increase of TMD peak was observed on the chromatograms measured at the end of the experiments at 50, 60, 70 and 80 °C. According to experience in handling and use of the test item, at temperatures above 50 °C, the test item starts to decompose to the starting materials (TMD and acrylonitrile ACN) which led to an increase in the TMD concentration and decrease in the concentration of the TMD-ACN adducts. Decrease of concentration stopped after an equilibrium composition was reached. Therefore, correlation between the time and the decrease of concentration of test substance was not significant. Regression coefficients of the linearized data were in the range of 0.6 – 0.8. Slightly better in case of second-order approximation.

Validity criteria fulfilled:
yes
Conclusions:
Based on the result of the test, the test item is considered to be hydrolytically stable at room temperature.
Executive summary:

The hydrolysis of the test item was assessed in accordance with the OECD guideline 111 and the EU method C.7 in a Tier 2 test. The hydrolysis of the test item in aqueous buffer solutions (pH = 7) at 12, 25, 50, 60, 70 and 80 °C was investigated using LC-MS. The content of test item in the pH buffer samples was determined at the beginning, the end of the test period and at each analytical occasion. Three samples of the test item solutions were analysed at the start of the study. Samples were 200-fold, 250-fold, or 500-fold diluted with ultra-pure water and then samples were analysed by LC/MS/MS method. The test item did not decompose at 12 °C and at 25 °C after 30 days incubation and no hydrolysis could be observed. Decomposition up to 58 % was observed at temperatures above 50 °C. Based on the results obtained, test substance cannot be considered as hydrolytically unstable at pH 7. Increase of TMD peak was observed on the chromatograms measured at the end of the experiments at 50, 60, 70 and 80 °C. According to experience in handling and use of the test item, at temperatures above 50 °C, the test item starts to decompose to the starting materials (TMD and acrylonitrile ACN) which led to an increase in the TMD concentration and decrease in the concentration of the TMD-ACN adducts. Decrease of concentration stopped after an equilibrium composition was reached. Therefore, correlation between the time and the decrease of concentration of test substance was not significant. Based on the result of the test, the test item is considered to be hydrolytically stable at room temperature.

Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
from 2018-08-16 to 2019-01-22
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
GLP compliance:
yes (incl. certificate)
Radiolabelling:
no
Analytical monitoring:
yes
Buffers:
- pH: 4, 7 and 9
- Composition of buffer:
pH 4.0: 1 mL 0.2 M Sodium hydroxide and 125 mL 0.2 M Potassium hydrogen phthalate was diluted to 500 mL with ultra-pure water.
pH 7.0: 74 mL 0.2 M Sodium hydroxide and 125 mL 0.2 M Potassium dihydrogen phosphate was diluted to 500 mL with ultra-pure water.
pH 9.0: 54 mL 0.2 M Sodium hydroxide and 125 mL 0.2 M Boric acid and Potassium chloride was diluted to 500 mL with ultra-pure water.
Details on test conditions:
TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: glass beakers
- Sterilisation method: using hot air steriliser
- Lighting: no
- Measures taken to avoid photolytic effects: The test was carried out using a dark thermostat to avoid photolytic effects.

TEST MEDIUM
- Kind and purity of water: ultrapure, sterile
- Preparation of test medium: Buffer solutions were preapred using reagent grade chemicals and ultrapure, sterile water.
- Renewal of test solution: not performed

OTHER TEST CONDITIONS
- Adjustment of pH: no
Duration:
5 d
pH:
4
Temp.:
50 °C
Duration:
5 d
pH:
7
Temp.:
50 °C
Duration:
5 d
pH:
9
Temp.:
50 °C
Preliminary study:
The preliminary test was performed at 50 ± 0.5 °C and pH 4, 7 and 9. More than 10 per cent of hydrolysis was observed after 5 days at pH 7. After the test period 1 % hydrolysis was calculated at pH 4, 23 % at pH 7 and 8 % at pH 9. Based on the results obtained, the test substance can be considered as hydrolytically stable at pH 4 and pH 9; and hydrolytically unstable at pH 7 under the conditions investigated.
Transformation products:
not measured
% Recovery:
99
pH:
4
Temp.:
50 °C
Duration:
5 d
% Recovery:
77
pH:
7
Temp.:
50 °C
Duration:
5 d
% Recovery:
92
pH:
9
Temp.:
50 °C
Duration:
5 d
Validity criteria fulfilled:
yes
Conclusions:
In the preliminary test was determined that the test item is hydroytically stable at pH 4 and 9 and hydrolytically unstable at pH 7.
Executive summary:

A preliminary test according to OECD 111 and EU Method C.7 was performed to determine the hydolysis potential of the test item. The preliminary test was performed at 50 ± 0.5 °C and pH 4, 7 and 9. After 5 days hydrolysis of more than 10 % was observed at pH 7 - in total 23 %. At pH 4 only 1 % hydrolysis and at pH 9 only 8 % were observed. Based on the results, the test substance can be considered as hydrolytically stable at pH 4 and 9, and hydrolytically unstable at pH 7 under the conditions investigated.

Description of key information

The test item is considered to be hydrolytically stable at room temperature.

Key value for chemical safety assessment

Additional information

Key study

The hydrolysis of the test item was assessed in accordance with the OECD guideline 111 and the EU method C.7 in a Tier 2 test. The hydrolysis of the test item in aqueous buffer solutions (pH = 7) at 12, 25, 50, 60, 70 and 80 °C was investigated using LC-MS. The content of test item in the pH buffer samples was determined at the beginning, the end of the test period and at each analytical occasion. Three samples of the test item solutions were analysed at the start of the study.Samples were 200-fold, 250-fold, or 500-fold diluted with ultra-pure water and then samples were analysed by LC/MS/MS method.The test item did not decompose at 12 °C and at 25 °C after 30 days incubation and no hydrolysis could be observed. Decomposition up to 58 % was observed at temperatures above 50 °C. Based on the results obtained, test substance cannot be considered as hydrolytically unstable at pH 7. Increase of TMD peak was observed on the chromatograms measured at the end of the experiments at 50, 60, 70 and 80 °C. According to experience in handling and use of the test item, at temperatures above 50 °C, the test item starts to decompose to the starting materials (TMD and acrylonitrile ACN) which led to an increase in the TMD concentration and decrease in the concentration of the TMD-ACN adducts. Decrease of concentration stopped after an equilibrium composition was reached. Therefore, correlation between the time and the decrease of concentration of test substance was not significant. Based on the result of the test, the test item is considered to be hydrolytically stable at room temperature.

Supporting study

A preliminary test according to OECD 111 and EU Method C.7 was performed to determine the hydolysis potential of the test item. The preliminary test was performed at 50 ± 0.5 °C and pH 4, 7 and 9. After 5 days hydrolysis of more than 10 % was observed at pH 7 - in total 23 %. At pH 4 only 1 % hydrolysis and at pH 9 only 8 % were observed. Based on the results, the test substance can be cosidered as hydrolytically stable at pH 4 and 9, and hydrolytically unstable at pH 7 under the conditions investigated.