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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:
29 June 2017 - 07 November 2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)
Version / remarks:
2008
Deviations:
no
Qualifier:
according to guideline
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Version / remarks:
2004
Deviations:
no
Qualifier:
according to guideline
Guideline:
EPA OPPTS 835.2120 (Hydrolysis of Parent and Degradates as a Function of pH at 25°C)
Version / remarks:
2008
Deviations:
no
GLP compliance:
yes
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
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.
Buffers:
- Acetate buffer pH 4, 0.1 M: Solution of 16.7% 0.1 M sodium acetate in water and 83.3% 0.1 M acetic acid in water. Buffer contained 0.0009% (w/v) sodium azide.
- Phosphate buffer pH 7, 0.1 M: Solution of 0.1 M potassium di-hydrogen-phosphate in water adjusted to pH 7 using 10N sodium hydroxide. Buffer contained 0.0009% (w/v) sodium azide.
- Borate buffer pH 9, 0.1 M: Solution of 0.1 M boric acid in water and 0.1 M potassium chloride in water adjusted to pH 9 using 10N sodium hydroxide. Buffer contained 0.0009% (w/v) sodium azide
Details on test conditions:
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 40 mg/L using a spiking solution in 50/50 (v/v) THF/water. For each sampling time, duplicate sterile vessels under vacuum were filled with 6 mL test solution and placed in the dark in a temperature controlled environment at 49.9°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 500 µL. The samples were diluted in a 1:1 (v:v) ratio with THF and analyzed. The blank buffer solutions were diluted in a 1:1 (v:v) ratio with THF 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.
Duration:
5 d
pH:
4
Temp.:
50 °C
Initial conc. measured:
ca. 40.1 mg/L
Remarks:
peak 1
Duration:
5 d
pH:
7
Temp.:
50 °C
Initial conc. measured:
ca. 40 mg/L
Remarks:
peak 1
Duration:
5 d
pH:
9
Temp.:
50 °C
Initial conc. measured:
ca. 39.4 mg/L
Remarks:
peak 1
Duration:
5 d
pH:
4
Temp.:
50 °C
Initial conc. measured:
ca. 39.8 mg/L
Remarks:
peak 2
Duration:
5 d
pH:
7
Temp.:
50 °C
Initial conc. measured:
ca. 40 mg/L
Remarks:
peak 2
Duration:
5 d
pH:
9
Temp.:
50 °C
Initial conc. measured:
ca. 41.8 mg/L
Remarks:
peak 2
Number of replicates:
Two
Positive controls:
no
Negative controls:
yes
Remarks:
Blank buffer solutions containing a similar content of blank spiking solution were treated similarly as the test samples and analyzed at t=0.
Preliminary study:
PEAK 1
- At pH 4, pH 7, and pH 9, a degree of hydrolysis of < 10% was observed after 5 days at 50°C. 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.

PEAK 2
- At pH 4, and pH 9, a degree of hydrolysis of < 10% was observed after 5 days at 50°C. 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.
- At pH 7, a degree of hydrolysis of > 10% was observed after 5 days. Since hydrolysis is not observed at pH 4 and pH 9, hydrolysis is not expected at pH 7. A possible explanation might be a limited solubility since at pH 7 later eluting peaks also have a lower response.
Based on this, it was decided not to perform the main study at pH 7 based on peak 2.
Test performance:
RECOVERY

PEAK 1
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.

PEAK 2
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.
Transformation products:
not measured
% Recovery:
100
pH:
4
Temp.:
50 °C
Duration:
5 d
Remarks on result:
other: peak1
% Recovery:
100
pH:
7
Temp.:
50 °C
Duration:
5 d
Remarks on result:
other: peak 1
% Recovery:
99
pH:
9
Temp.:
50 °C
Duration:
5 d
Remarks on result:
other: peak 1
% Recovery:
99
pH:
4
Temp.:
50 °C
Duration:
5 d
Remarks on result:
other: peak 2
% Recovery:
100
pH:
7
Temp.:
50 °C
Duration:
5 d
Remarks on result:
other: peak 2
% Recovery:
105
pH:
9
Temp.:
50 °C
Duration:
5 d
Remarks on result:
other: peak 2
Key result
pH:
4
Temp.:
50 °C
DT50:
> 1 yr
Type:
not specified
Remarks on result:
other: peak 1
Key result
pH:
7
Temp.:
50 °C
DT50:
> 1 yr
Type:
not specified
Remarks on result:
other: peak 1
Key result
pH:
9
Temp.:
50 °C
DT50:
> 1 yr
Type:
not specified
Remarks on result:
other: peak 1
Key result
pH:
4
Temp.:
50 °C
DT50:
> 1 yr
Type:
not specified
Remarks on result:
other: peak 2
Key result
pH:
7
Temp.:
50 °C
DT50:
> 1 yr
Type:
not specified
Remarks on result:
other: peak 2
Remarks:
expected result
Key result
pH:
9
Temp.:
50 °C
DT50:
> 1 yr
Type:
not specified
Remarks on result:
other: peak 2
Details on results:
At pH 7, a degree of hydrolysis of > 10% was observed after 5 days at 50°C for peak 2. Since hydrolysis is not observed at pH 4 and pH 9, hydrolysis is not expected at pH 7. A possible explanation might be a limited solubility since at pH 7 later eluting peaks also have a lower response. Based on this, it was decided not to perform the main study at pH 7 based on peak 2.

Preliminary Test: Hydrolysis of the Test Item at pH 4, pH 7 and pH 9 – Based on peak 1

pH code

Sampling time

Analyzed concentration
[mg/L]

Degree of hydrolysis
[%]

pH

Individual

Mean

pH 4

0 hours

40.1

 

 

3.9

 

 

40.1

 

 

4.0

 

5 days

39.7

1.1

1.1

4.0

 

 

39.7

1.1

 

4.0

pH 7

0 hours

39.7

 

 

7.1

 

 

40.2

 

 

7.1

 

5 days

38.6

3.3

2.6

7.0

 

 

39.2

2.0

 

7.1

pH 9

0 hours

39.6

 

 

9.1

 

 

39.3

 

 

9.1

 

5 days

40.3

-2.2

-1.9

9.1

 

 

40.1

-1.7

 

9.1

Preliminary Test: Hydrolysis of the Test Item at pH 4, pH 7 and pH 9 – Based on peak 2

pH code

Sampling time

Analyzed concentration
[mg/L]

Degree of hydrolysis
[%]

pH

Individual

Mean

pH 4

0 hours

40.5

 

 

3.9

 

 

39.0

 

 

4.0

 

5 days

37.9

4.7

4.7

4.0

 

 

37.8

4.8

 

4.0

pH 7

0 hours

39.9

 

 

7.1

 

 

40.2

 

 

7.1

 

5 days

31.4

22

21

7.0

 

 

31.7

21

 

7.1

pH 9

0 hours

43.8

 

 

9.1

 

 

39.9

 

 

9.1

 

5 days

37.8

9.6

8.2

9.1

 

 

39.0

6.9

 

9.1

Preliminary Test: Recoveries –Based on peak 1

pH code

Nominal concentration
[mg/L]

Analyzed concentration
[mg/L]

Recovery
[%]

Individual

Mean

pH 4

40.0

40.1

100

100

 

40.0

40.1

100

 

pH 7

40.0

39.7

99

100

 

40.0

40.2

100

 

pH 9

40.0

39.6

99

99

 

40.0

39.3

98

 

Preliminary Test: Recoveries – Based on peak 2

pH code

Nominal concentration
[mg/L]

Analyzed concentration
[mg/L]

Recovery
[%]

Individual

Mean

pH 4

40.0

40.5

101

99

 

40.0

39.0

97

 

pH 7

40.0

39.9

100

100

 

40.0

40.2

101

 

pH 9

40.0

43.8

109

105

 

40.0

39.9

100

 

 


 

Validity criteria fulfilled:
yes
Remarks:
It demonstrated that the analytical method was adequate to support the hydrolysis study on the test item
Conclusions:
The rate of the hydrolysis of the test item was determined according to OECD Guideline No 111, EC Guideline No. C.7, EPA OPPTS 835.2120.
A preliminary test (Tier 1) was performed at pH values normally found in the environment (pH 4 - 7 - 9). The degree of hydrolysis was determined after 5 days at 50°C.  The quantification was based on the two major peaks in the chromatogram.
It demonstrated that the half-life time of peak 1 at 25°C is > 1 year, at all the three values of pH. It demonstrated that the half-life time of peak 2 at 25°C is > 1 year at pH 4 and 9. It is expected to be > 1 year at 25°C also at pH 7.
According to the guideline, performance of the main study (Tier 2) was not required.
Executive summary:

The rate of the hydrolysis of the test item was determined according to OECD Guideline No 111, EC Guideline No. C.7, EPA OPPTS 835.2120 and GLP principles.

A preliminary test (Tier 1) was performed at pH values normally found in the environment (pH 4 - 7 - 9). The quantification was based on the two major peaks in the chromatogram.

Based on peak 1, at each pH value a degree of hydrolysis of < 10% was observed after 5 days at 50°C. It demonstrated that the half-life time of the test item at 25°C is > 1 year. According to the guideline, performance of the main study (Tier 2) was not required.

Based on peak 2, at pH 4, and pH 9, a degree of hydrolysis of < 10% was observed after 5 days at 50°C. 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. At pH 7, a degree of hydrolysis of > 10% was observed after 5 days at 50°C. Since hydrolysis was not observed at pH 4 and pH 9, hydrolysis was not expected at pH 7. A possible explanation might be a limited solubility since at pH 7 later eluting peaks also have a lower response. Based on this, it was decided not to perform the main study at pH 7 based on peak 2.

Description of key information

The objective of this study was the determination of the rate of the hydrolysis of the test item, according to OECD Guideline No 111,EC Guideline No. C.7, EPA OPPTS 835.2120 and GLP principles.

A preliminary test (Tier 1) was performed at pH values normally found in the environment (pH 4 - 7 - 9). The quantification was based on the two major peaks in the chromatogram.

Based on peak 1, at each pH value a degree of hydrolysis of < 10% was observed after 5 days at 50°C. It demonstrated that the half-life time of the test item at 25°C is > 1 year. According to the guideline, performance of the main study (Tier 2) was not required.

Based on peak 2, at pH 4, and pH 9, a degree of hydrolysis of < 10% was observed after 5 days at 50°C. 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. 

At pH 7, a degree of hydrolysis of > 10% was observed after 5 days at 50°C. Since hydrolysis was not observed at pH 4 and pH 9, hydrolysis was not expected at pH 7. A possible explanation might be a limited solubility since at pH 7 later eluting peaks also have a lower response. Based on this, it was decided not to perform the main study at pH 7 based on peak 2.

Key value for chemical safety assessment

Half-life for hydrolysis:
1 yr
at the temperature of:
25 °C

Additional information