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Hydrolysis

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Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
November 27th, 2012 - April 7th, 2013
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)
Version / remarks:
(2008)
Deviations:
no
Qualifier:
according to
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Version / remarks:
(2004)
Deviations:
no
Qualifier:
according to
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:
Samples for analysis were taken 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, 0.01 M: solution of 16.7% 0.01 M sodium acetate in water and 83.3% 0.01 M acetic acid in water. The buffer contains 0.0009% (w/v) sodium azide.

Phosphate buffer pH 7, 0.01 M: solution of 0.01 M potassium di-hydrogenphosphate in water adjusted to pH 7 using 1 N sodium hydroxide. The buffer contains 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 1 N sodium hydroxide. The buffer contains 0.0009% (w/v) sodium azide.
Details on test conditions:
Performance of the study:
The rate of hydrolysis of the test substance as a function of pH was determined at pH values normally found in the environment (pH 4-9).

Preliminary test - Tier 1:
The test substance was spiked to the buffer solutions at a target concentration of 20 mg/L using a spiking solution in water. Each solution was 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. 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 concentration of the test substance 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. The samples were diluted with buffer solution to obtain a concentration within the calibration range.

Blank buffer solutions containing a similar content of blank spiking solution were treated similarly as the test samples and analysed at t=0.

The pH of each of the test solutions (except for the blanks) was determined at each sampling time.
Number of replicates:
Two
Positive controls:
no
Negative controls:
no
Preliminary study:
At pH 4, 7 and pH 9, < 10% of hydrolysis was observed after 5 day (half-life time at 25°C is > 1 year). According to the guideline, no further tests were required.
Test performance:
RECOVERIES
- Recovery is the concentration analysed at t=0 relative to the nominal concentration.
- Mean recovery in the table below is the mean of duplicate test samples.
- The mean recoveries of all the buffer solutions fell within he acceptable range of 90-110%; the analytical method was adequate to support the hydrolysis study on the test substance.
Transformation products:
not measured
% Recovery:
107
pH:
4
Temp.:
50 °C
Duration:
5 d
% Recovery:
102
pH:
7
Temp.:
50 °C
Duration:
5 d
% Recovery:
101
pH:
9
Temp.:
50 °C
Duration:
5 d
Key result
Remarks on result:
hydrolytically stable based on preliminary test
Details on results:
The analytical results of the preliminary test are given in the table hereunder.

At pH 4, pH 7 and pH 9 a degree of hydrolysis of < 10% was observed after 5 days. It demonstrated that the half-life time of the test substance at 25°C is > 1 year. According to the guideline, no further tests were required.

No test substance was detected in the blank buffer solutions.

The mean recoveries of the buffer solutions fell within the criterion range of 90-110%. It demonstrated that the analytical method was adequate to support the hydrolysis study on the test substance.

Table. Preliminary test - hydrolysis of the substance at pH 4, pH 7 and pH 9 at 50.0 ±1 °C:

pH code

Sampling time

Analysed concentration
[mg/l]

Degree of hydrolysis
[%]

Actual pH

Individual

Mean

 

 

 

 

 

 

pH 4

0 hours

21.6

 

 

4.1

 

 

21.4

 

 

4.1

 

 

 

 

 

 

 

5 days

20.9

2.8

3.3

4.1

 

 

20.7

3.8

 

4.1

 

 

 

 

 

 

pH 7

0 hours

20.5

 

 

7.0

 

 

20.5

 

 

7.1

 

 

 

 

 

 

 

5 days

19.4

5.1

4.7

7.0

 

 

19.6

4.3

 

7.0

 

 

 

 

 

 

pH 9

0 hours

20.1

 

 

9.0

 

 

20.1

 

 

9.0

 

 

 

 

 

 

 

5 days

19.5

3.0

2.9

9.0

 

 

19.6

2.8

 

9.0

 

 

 

 

 

 

Validity criteria fulfilled:
yes
Conclusions:
A hydrolysis study was carried out according to EC C.7, OECD 111, EPA OPPTS 830.2120 and GLP. At pH 4, 7 and 9 and 50 °C, a degree of < 10% of hydrolysis was observed after 5 days. This corresponds with a half-life time at 25°C of > 1 year; the substance can be considered hydrolytically stable at pH 4, 7 and 9.

Description of key information

In a Tier 1 study (in accordance with EC C.7, OECD 111, EPA OPPTS 830.2120) , < 10% of hydrolysis was observed at pH 4, 7 and 9  after 5 days at 50 °C. Therefore the half-life time at 25°C is > 1 year and the substance can be considered hydrolytically stable at pH 4, 7 and 9.

Key value for chemical safety assessment

Additional information

Half-life for hydrolysis is > 1 year at 25°C.