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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:
13 September 2012 to 12 December 2012
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:
not specified
Analytical monitoring:
yes
Details on sampling:
Dupicate aliquots of test material were sampled for each buffer. The sample solutions were taken from the waterbath at various times and the pH of each solution recorded before concentration was determined.
Buffers:
- pH: 4, 7 and 9
- Composition of pH 4 buffer: Citric acid 6 mmol/dm³, sodium chloride 4 mmol/dm³ and sodium hydroxide 7 mmol/dm³.
- Composition of pH 7 buffer: Disodium hydrogen orthophosphate 3 mmol/dm³, potassium dihydrogen orthophosphate 2 mmol/dm³ and sodium chloride 2 mmol/dm³.
- Composition of pH 9 buffer: Disodium tetraborate 1 mmol/dm³ and sodium chloride 2 mmol/dm³.
Details on test conditions:
TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: Stoppered glass flasks
- Measures taken to avoid photolytic effects: The test solutions were shielded from light whilst maintained at test temperature.
- Measures to exclude oxygen: The buffer solutions were subjected to ultrasonication and degassing with nitrogen to minimise dissolved oxygen content.
- If no traps were used, is the test system closed/open: Closed (stoppered flasks)
- Is there any indication of the test material adsorbing to the walls of the test apparatus?: Not reported

PREPARATION OF THE TEST SOLUTIONS
Sample solutions were prepared in stoppered glass flasks at a nominal concentration of 200 mg/L in the three buffer solutions. A 1 % co-solvent of methanol was used to aid solubility. The concentration of each solution did not exceed the lesser of 0.01 mol/L or half the water solubility. The test solutions were split into individual vessels for each data point.

PRELIMINARY TEST - TIER 1
Sample solutions at pH 4, 7 and 9 were maintained at 50.0 ± 0.5 °C for a period of 120 hours.

TIER 2
Results from the Preliminary Test/Tier 1 showed it was not necessary to undertake any further testing.
Duration:
120 h
pH:
4
Temp.:
50 °C
Initial conc. measured:
0.203 g/L
Duration:
120 h
pH:
7
Temp.:
50 °C
Initial conc. measured:
0.203 g/L
Duration:
120 h
pH:
9
Temp.:
50 °C
Initial conc. measured:
0.206 g/L
Number of replicates:
Two replicates per pH
Positive controls:
no
Negative controls:
no
Preliminary study:
In the Tier 1 preliminary test less than 10 % hydrolysis was seen after 5 days at 50 °C, equivalent to a half-life greater than 1 year at 25 °C, for all three buffer solutions.
Therefore no further testing was required.
Transformation products:
no
Key result
pH:
4
Temp.:
25 °C
DT50:
> 1 yr
Remarks on result:
hydrolytically stable based on preliminary test
Key result
pH:
7
Temp.:
25 °C
DT50:
> 1 yr
Remarks on result:
hydrolytically stable based on preliminary test
Key result
pH:
9
Temp.:
25 °C
DT50:
> 1 yr
Remarks on result:
hydrolytically stable based on preliminary test

Table 1: Results at pH 4 (50.0 ± 0.5 °C)

Time (Hours)

Concentration

(g/L)

% of Mean Initial Concentration

A

B

A

B

0

0.202

0.203

-

-

24

0.196

0.197

96.5

97.3

120

0.193

0.194

95.3

96.0

Less than 10 % hydrolysis after 5 days at 50 °C, equivalent to a half-life greater than 1 year at 25 °C.

Table 2: Results at pH 7 (50.0 ± 0.5 °C)

Time (Hours)

Concentration

(g/L)

% of Mean Initial Concentration

A

B

A

B

0

0.203

0.202

-

-

24

0.201

0.200

99.3

98.9

120

0.200

0.199

98.7

98.2

Less than 10 % hydrolysis after 5 days at 50 °C, equivalent to a half-life greater than 1 year at 25 °C.

Table 3: Results at pH 9 (50.0 ± 0.5 °C)

Time (Hours)

Concentration

(g/L)

% of Mean Initial Concentration

A

B

A

B

0

0.205

0.206

-

-

24

0.210

0.209

102

102

120

0.212

0.210

103

102

Less than 10 % hydrolysis after 5 days at 50 °C, equivalent to a half-life greater than 1 year at 25 °C.

Validity criteria fulfilled:
not specified
Conclusions:
Under the conditions of this study, the test material was estimated to have a half-life >1 year at pH 4, 7 and 9 at 25 °C.
Executive summary:

A study was conducted to investigate the potential hydrolysis as a function of pH of the test material in accordance with the standardised guidelines OECD 111 and EU Method C.7 under GLP conditions.

The potential of the test material to undergo hydrolysis was investigated at buffer solutions prepared at pH 4, 7 and 9 at 50 °C in the dark for a period of five days. The buffer solutions were subjected to ultrasonication and degassing with nitrogen to minimise dissolved oxygen content.

Changes in the concentration of test material were monitored after 24 and 120 h using HPLC analysis with UV detection at 288 nm.

Less than 10 % hydrolysis was seen after 120 hours at 50 °C for all three buffers.

Under the conditions of this study, the test material was estimated to have a half-life >1 year at pH 4, 7 and 9 at 25 °C.

Description of key information

The test material was estimated to have a half-life >1 year at pH 4, 7 and 9 at 25 °C.

Key value for chemical safety assessment

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

Additional information

A study was conducted to investigate the potential hydrolysis as a function of pH of the test material in accordance with the standardised guidelines OECD 111 and EU Method C.7 under GLP conditions. The study was assigned a reliability score of 1 in accordance with the criteria for assessing data quality set forth by Klimisch et al. (1997).

The potential of the test material to undergo hydrolysis was investigated at buffer solutions prepared at pH 4, 7 and 9 at 50 °C in the dark for a period of five days. The buffer solutions were subjected to ultrasonication and degassing with nitrogen to minimise dissolved oxygen content.

Changes in the concentration of test material were monitored after 24 and 120 h using HPLC analysis with UV detection at 288 nm.

Less than 10 % hydrolysis was seen after 120 hours at 50 °C for all three buffers.

Under the conditions of this study, the test material was estimated to have a half-life >1 year at pH 4, 7 and 9 at 25 °C.