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Hydrolysis

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Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
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)
Deviations:
no
GLP compliance:
yes
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
- Sampling intervals for the parent/transformation products:
- Sampling method: Samples were taken directly from vessels. Samples were taken and filtered using a pretreatment filter. These samples were then cooled and analysed via HPLC.
- Sampling intervals/times for pH measurements:
20°C pH 7: days 0, 13, 17, 21, 24, 27 and 30 (7 in total).
20°C pH 9: All measurements (7 in total) taken on the first day.
40°C pH7: days 0, 1, 2 and 3 (7 samples taken in total).
40°C pH9: All measurements (7 in total) taken on the first day.
50°C pH7: days 0 and 1(7 in total).
50°C pH9: All measurements (7 in total) taken on the first day.

- Sampling intervals/times for sterility check: Not conducted
- Sample storage conditions before analysis: analysed soon after sampling
- Other observation, if any (e.g.: precipitation, color change etc.): None noted
Buffers:
- pH: 7 and 9
- Composition of buffer: pH7 (Mixture of 0.1N NaOH and 0.1 M KH2PO4 diluted in ultrapure water. pH 9 (Mixture of 0.1N NaOH and 0.1M KCl/0.1M H3BO3 diluted in ultrapure water. pH 9 (Mixture of 0.1N NaOH and 0.1M KCl/0.1M H3BO3 diluted with ultra-pure water.
Estimation method (if used):
Not applicable
Details on test conditions:
TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: Glass culture bottle or glass flask with a test volume of 300 mL
- Sterilisation method: Not specified
- Lighting: shielded from light
- Is there any indication of the test material adsorbing to the walls of the test apparatus? No
TEST MEDIUM
- Volume used/treatment: 300 mL of test solution (10 mg/L)
- Kind and purity of water: Ultra-pure water
- Preparation of test medium: The test substance was weighed then dissolved and diluted with acetonitrile to prepare a stock solution. Aliquots of this stock solution were sampled and added to appropriate buffer solutions in a flask for shaking or culture bottle.
- Renewal of test solution: Not conducted
- Identity and concentration of co-solvent: Acetonitrile (concentration not specified)
OTHER TEST CONDITIONS
- Adjustment of pH: Not specified
- Dissolved oxygen: Not specified
Duration:
30 d
pH:
7
Temp.:
20 °C
Initial conc. measured:
ca. 10 mg/L
Duration:
0 d
pH:
9
Temp.:
20 °C
Initial conc. measured:
ca. 10 mg/L
Duration:
3 d
pH:
7
Temp.:
40 °C
Initial conc. measured:
ca. 10 mg/L
Duration:
0 d
pH:
9
Temp.:
40 °C
Initial conc. measured:
ca. 10 mg/L
Duration:
1 d
pH:
7
Temp.:
50 °C
Initial conc. measured:
ca. 10 mg/L
Duration:
0 d
pH:
9
Temp.:
50 °C
Initial conc. measured:
ca. 10 mg/L
Number of replicates:
7 Replicates were used for each pH/temperature.
Positive controls:
no
Negative controls:
yes
Remarks:
Buffer solutions
Statistical methods:
Not applicable
Preliminary study:
In the Tier 1 test, the substance was added to buffer solutions of pH 4, 7 and 9. After 5 days of treatment at 50°C a concentration of the test substance was measured in the buffer solutions. As a result, the test substance was considered hydrolytically stable at pH 4 because the hydrolysis of the test substance was less than 10%. The test substance was considered hydrolytically unstable at pH 7 and 9 as hydrolysis was greater than 10%. Accordingly the Tier 2 assesment was conducted at pH 7 and 9.
Test performance:
The test was considered valid if recovery of the test item was between 90 and 110% and the method is suitably sensitive. These criteria were met indicating the validity of the test.
Transformation products:
no
Remarks:
Hydrolysis of the test substance was observed at pH 7 and 9 with multiple peaks detected on the HPLC chromatogram. Attempts were made using LC/MS to identify these although this was not possible.
Details on hydrolysis and appearance of transformation product(s):
Molecular weights of around 170 to 500 were inferred to the molecular weight of the test substance (158.16), so that a change in the quinone structure of the test substance and polymerisation were presumed, but the structural formulas themselves could not be identified.
% Recovery:
99.7
pH:
7
Temp.:
20 °C
Duration:
30 d
% Recovery:
100
pH:
7
Temp.:
40 °C
Duration:
3 d
% Recovery:
100
pH:
7
Temp.:
50 °C
Duration:
1 d
% Recovery:
96.7
pH:
9
Temp.:
20 °C
Duration:
0 d
% Recovery:
100
pH:
9
Temp.:
40 °C
Duration:
0 d
% Recovery:
98.7
pH:
9
Temp.:
50 °C
Duration:
0 d
pH:
7
Temp.:
25 °C
Hydrolysis rate constant:
0.002 h-1
DT50:
12 d
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: Result extrapolated from graph using Arrhenius data
pH:
9
Temp.:
25 °C
Hydrolysis rate constant:
0.159 h-1
DT50:
4 h
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: Result extrapolated from graph using Arrhenius data
pH:
7
Temp.:
20 °C
Hydrolysis rate constant:
0.001 h-1
DT50:
21 d
Type:
(pseudo-)first order (= half-life)
pH:
7
Temp.:
40 °C
Hydrolysis rate constant:
0.01 h-1
DT50:
2.9 d
Type:
(pseudo-)first order (= half-life)
pH:
7
Temp.:
50 °C
Hydrolysis rate constant:
0.03 h-1
DT50:
23 h
Type:
(pseudo-)first order (= half-life)
pH:
9
Temp.:
20 °C
Hydrolysis rate constant:
0.096 h-1
DT50:
7.3 h
Type:
(pseudo-)first order (= half-life)
pH:
9
Temp.:
40 °C
Hydrolysis rate constant:
0.618 h-1
DT50:
1.1 h
Type:
(pseudo-)first order (= half-life)
pH:
9
Temp.:
50 °C
Hydrolysis rate constant:
1.37 h-1
DT50:
0.5 h
Type:
(pseudo-)first order (= half-life)
Details on results:
TEST CONDITIONS
- pH, sterility, temperature, and other experimental conditions maintained throughout the study: Yes
- Anomalies or problems encountered (if yes): No

MAJOR TRANSFORMATION PRODUCTS
Could not be conclusively identified although a change in test structure and polymerisation were presumed.

PATHWAYS OF HYDROLYSIS
- Description of pathways: Not identified.

Results with reference substance:
Not applicable
Validity criteria fulfilled:
yes
Conclusions:
The test substance is considered hydrolytically unstable at pH 7 and 9. It is assumed based on the results that the substance would be more readily hydrolysed in alkaline conditions as opposed to acidic conditions.

Description of key information

A GLP, guideline OECD 111 study is available providing hydrolysis data on the substance. The key value is interpolated from values at 20, 40 and 50°C using the Arrhenius equation to 25°C and pH 7.

The substance is more hydrolytically unstable at a higher alkaline pH although will hydrolyse at environmentally relevant temperatures and pH values.

Key value for chemical safety assessment

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

Additional information