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Hydrolysis

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Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
15 June 2018 to 17 July 2018
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Version / remarks:
2004
Deviations:
no
GLP compliance:
yes
Radiolabelling:
not specified
Analytical monitoring:
yes
Buffers:
Preparation of buffer solution
- pH 4.0: The solution was prepared by mixing 4.5 mL of 1 mol/L sodium hydroxide solution and 50 mL of 0.5 mol/L potassium dihydrogen citrate solution and then filling up to 500 mL with purified water.
- pH 7.0: The solution was prepared by mixing 14 .8 mL of 1 mol/L sodium hydroxide solution and 50 mL of 0.5 mol/L potassium dihydrogenphosphate solution and then filling up to 500 mL with purified water.
- pH 9.0: The solution was prepared by mixing 10.7 mL of 1 mol/L sodium hydroxide solution and 50 mL of 0.5 mol/L potassium chloride and 0.5 mol/L boric acid solution, and then filling up to 500 mL with purified water.
- Each buffer solution was adjusted to nominated pH with 1 mol/L hydrochloric acid and/or 1 mol/L sodium hydroxide solution as necessary.
- The buffer solution was filtrated with a sterile filter (0.2 μm) after the preparation.
Details on test conditions:
TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: 10 mL test tube with glass stopper
- Sterilisation method: The glassware for preparation of test solution in a) and b) were sterilised with ethanol in advance.
- The test material sample (100.3 mg) was precisely weighed with an electronic analytical balance and then filled up to 50 mL with acetonitrile to obtain 2010 mg/L test material solution.
- A portion (2 mL) of the test material solution (test material: 4 mg) was put into a 200-mL volumetric flask and then filled up with each buffer solution which was aerated for about 5 minutes with helium gas to obtain a test solution.
- The test solution (about 7 mL) was divided into some test vessels at each pH
- At initiation, one test solution in each pH was pre-treated and analysed. The remaining test solutions were put into the thermostat and warmed at the test temperature.
- At the measurement point, two test solutions were taken out from the thermostat and were cooled to room temperature, and then were pre-treated and analysed.
- Test concentration: About 20 mg/L
- Measurement point: At initiation and 6 points in test duration (at each temperature and pH)
- Number of test repetitions:
At initiation: 1 (at each temperature and pH)
At each measurement point: 2 (at each temperature and pH)
- Light condition: Protection from light (The test vessels were covered with aluminium foil)
Duration:
8 d
pH:
4
Temp.:
30 °C
Initial conc. measured:
19.2 mg/L
Duration:
3 d
pH:
4
Temp.:
40 °C
Initial conc. measured:
19.1 mg/L
Duration:
26 h
pH:
4
Temp.:
50 °C
Initial conc. measured:
18.1 mg/L
Duration:
13 d
pH:
7
Temp.:
35 °C
Initial conc. measured:
19.4 mg/L
Duration:
90 h
pH:
7
Temp.:
45 °C
Initial conc. measured:
19.8 mg/L
Duration:
34 h
pH:
7
Temp.:
55 °C
Initial conc. measured:
19.4 mg/L
Duration:
14 d
pH:
9
Temp.:
35 °C
Initial conc. measured:
18.5 mg/L
Duration:
4 d
pH:
9
Temp.:
45 °C
Initial conc. measured:
19.5 mg/L
Duration:
34 h
pH:
9
Temp.:
55 °C
Initial conc. measured:
17.7 mg/L
Number of replicates:
At initiation: 1 (at each temperature and pH)
At each measurement point: 2 (at each temperature and pH)
Positive controls:
no
Negative controls:
no
Preliminary study:
The hydrolysis test (Tier 2) was conducted because the test material was hydrolysed in a preliminary test.
Test performance:
The results of hydrolysis rate constant and half-life at 25 °C are considered to be acceptable because the regression equation about logarithm values of the hydrolysis rate constants versus reciprocal number of the respective absolute temperature (1/T) at each pH was confirmed to be a straight line.
As the colony was not counted after the test, it was considered that sterile conditions were maintained. Therefore, the microorganism was not affected the results of the hydrolysis test.
Transformation products:
not specified
Remarks:
Hydrolysis products were observed. Please refer to the attachment for further information on the chemical identity.
Details on hydrolysis and appearance of transformation product(s):
Hydrolysis products were observed (please see attachment). At retention times of around 9 and 9.5-9.7 minutes a hydrolysis product with a presumed molecular weight of 388 was detected. This transformation product was observed with the following detection ions (m/z) [and attributions]: 389 [M1a + H]+, 411 [M1a + Na]+ and 427 [M1a + K]+. At a retention time of around 10.5 minutes a hydrolysis product with a presumed molecular weight of 370 was detected. This transformation product was observed with the following detection ions (m/z) [and attributions]: 371 [M2 + H]+, 388 [M2 + NH4]+, 393 [M2 + Na]+ and 409 [M2 + K]+.
Key result
pH:
4
Temp.:
25 °C
Hydrolysis rate constant:
0.006 h-1
DT50:
5.14 d
Type:
not specified
Key result
pH:
7
Temp.:
25 °C
Hydrolysis rate constant:
0.002 h-1
DT50:
13.7 d
Type:
not specified
Key result
pH:
9
Temp.:
25 °C
Hydrolysis rate constant:
0.002 h-1
DT50:
16.5 d
Type:
not specified

Table 1: Hydrolysis rate constant and half life at test temperatures

pH

Temperature (°C)

Rate Constant (hour^-1)

Half Life (hours)

Measured Value

Average

Measured Value

Average

4.0

30

9.97 x 10^-3

9.87 x 10^-3

69.5

70.2

9.78 x 10^-3

70.8

40

2.51 x 10^-2

2.50 x 10^-2

27.6

27.7

2.49 x 10^-2

27.9

50

7.20 x 10^-2

7.12 x 10^-2

9.63

9.73

7.05 x 10^-2

9.83

7.0

35

6.72 x 10^-3

6.72 x 10^-3

103

103

6.72 x 10^-3

103

45

1.55 x 10^-2

1.52 x 10^-2

44.8

45.6

1.50 x 10^-2

46.3

55

4.87 x 10^-2

4.91 x 10^-2

14.2

14.1

4.94 x 10^-2

14.0

9.0

35

5.34 x 10^-3

5.34 x 10^-3

130

130

5.34 x 10^-3

130

45

1.64 x 10^-2

1.65 x 10^-2

42.3

42.1

1.65 x 10^-2

42.0

55

4.24 x 10^-2

4.20 x 10^-2

16.3

16.5

4.16 x 10^-2

16.7

Validity criteria fulfilled:
not specified
Conclusions:
Under the conditions of this study the half-life of the test material at 25 °C was 5.14, 13.7 and 16.5 days at pH 4, 7 and 9, respectively. The rate constant was 5.62 x 10^-3, 2.11 x 10^-3 and 1.75 x 10^-3 hours^-1 at pH 4, 7 and 9, respectively.
Executive summary:

 Hydrolysis as a function of pH of the test material was investigated in accordance with the standardised guideline OECD 111, under GLP conditions.

The hydrolysis test (Tier 2) was conducted because the test material was hydrolysed in a preliminary test. The test was performed at pH 4.0 at 30, 40 and 50 °C for 8 days, 3 days and 26 hours, respectively. The test was performed at pH 7.0 at 35, 45 and 55 °C for 13 days, 90 hours and 34 hours, respectively. The test was performed at pH 9.0 at 35, 45 and 55 °C for 14 days, 4 days and 34 hours, respectively. The initial concentrations of the test material used were about 20 mg/L.

The results of hydrolysis rate constant and half-life at 25 °C are considered to be acceptable because the regression equation about logarithm values of the hydrolysis rate constants versus reciprocal number of the respective absolute temperature (1/T) at each pH was confirmed to be a straight line.

As the colony was not counted after the test, it was considered that sterile conditions were maintained. Therefore, the microorganism was not affected the results of the hydrolysis test.

Hydrolysis products were observed but not identified. At retention times of around 9 and 9.5-9.7 minutes a hydrolysis product with a presumed molecular weight of 388 was detected and at a retention time of around 10.5 minutes a hydrolysis product with a presumed molecular weight of 370 was detected.

Under the conditions of this study the half-life of the test material at 25 °C was 5.14, 13.7 and 16.5 days at pH 4, 7 and 9, respectively. The rate constant was 5.62 x 10^-3, 2.11 x 10^-3 and 1.75 x 10^-3 hours^-1 at pH 4, 7 and 9, respectively.

Description of key information

Under the conditions of this study the half-life of the test material at 25 °C was 5.14, 13.7 and 16.5 days at pH 4, 7 and 9, respectively. The rate constant was 5.62 x 10^-3, 2.11 x 10^-3 and 1.75 x 10^-3 hours^-1 at pH 4, 7 and 9, respectively.

Key value for chemical safety assessment

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

Additional information

 Hydrolysis as a function of pH of the test material was investigated in accordance with the standardised guideline OECD 111, under GLP conditions. The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).

The hydrolysis test (Tier 2) was conducted because the test material was hydrolysed in a preliminary test. The test was performed at pH 4.0 at 30, 40 and 50 °C for 8 days, 3 days and 26 hours, respectively. The test was performed at pH 7.0 at 35, 45 and 55 °C for 13 days, 90 hours and 34 hours, respectively. The test was performed at pH 9.0 at 35, 45 and 55 °C for 14 days, 4 days and 34 hours, respectively. The initial concentrations of the test material used were about 20 mg/L.

The results of hydrolysis rate constant and half-life at 25 °C are considered to be acceptable because the regression equation about logarithm values of the hydrolysis rate constants versus reciprocal number of the respective absolute temperature (1/T) at each pH was confirmed to be a straight line.

As the colony was not counted after the test, it was considered that sterile conditions were maintained. Therefore, the microorganism was not affected the results of the hydrolysis test.

Hydrolysis products were observed but not identified. At retention times of around 9 and 9.5-9.7 minutes a hydrolysis product with a presumed molecular weight of 388 was detected and at a retention time of around 10.5 minutes a hydrolysis product with a presumed molecular weight of 370 was detected.

Under the conditions of this study the half-life of the test material at 25 °C was 5.14, 13.7 and 16.5 days at pH 4, 7 and 9, respectively. The rate constant was 5.62 x 10^-3, 2.11 x 10^-3 and 1.75 x 10^-3 hours^-1 at pH 4, 7 and 9, respectively.