Registration Dossier

Environmental fate & pathways

Hydrolysis

Currently viewing:

Administrative data

Link to relevant study record(s)

Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
24-09-2001 to 24-01-2002
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Guideline study performed under GLP. All relevant validity criteria were met.
Remarks:
GLP; well documented study report following a screening study and method to guideline with acceptable deviations according to the regulatory conclusion that the substance is hydrolytically unstable under specific conditions. The study would not fulfil the EU Method C.7 or OECD TG 111 (2004) Tier 3 requirements.
Qualifier:
according to
Guideline:
EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)
Deviations:
no
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Deviations:
no
Principles of method if other than guideline:
The test followed a method in accordance with EU Method C.7 and equivalent or similar to OECD TG 111 (hydrolysis as a function of pH) - as a screening study (tier 1) for the hydrolysis properties of the test substance and/or determination of hydrolysis rate constants (tier 2). Specific identification of hydrolysis products (tier 3) was not performed.
GLP compliance:
yes (incl. certificate)
Remarks:
inspected: February 2000; signature: April 2000
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
- Sampling intervals for the parent/transformation products:
Preliminary test (tier 1): 0 hours, 2.4, 4, 6, 22.5, 24, 48, 74 and 92.5 hours (as appropriate depending on results).
Definitive test (tier 2): 0 hours, 43.3, 91.5, 92.0, 164, 211 hours.
In both the tier 1 and tier 2 tests other time periods may have been measured (recorded in the primary data but not included in the presented results).
- Sampling method: Aliquots of the sample solutions were taken from the flasks at various times and the pH of each solution recorded. The concentrations were determined by Gas Chromatography (GC). Duplicate aliquots (100 mL) of each sample were extracted with three portions (3 x 25 mL) of dichloromethane, each extract being filtered through anhydrous sodium sulphate. The combined extracts were evaporated to dryness and the residue re-dissolved in acetone (10 mL). For standards: Duplicate standard solutions of test material were prepared in acetone at a nominal concentration of 25 mg/L.
- Sampling methods for the volatile compounds, if any: Not applicable.
- Sampling intervals/times for pH measurements: Not reported.
- Sampling intervals/times for sterility check: The buffer solutions were filtered through a 0.2 µm membrane filter and subject to sonification and degassing. Thereby ensuring sterility of the test system.
- Sample storage conditions before analysis: On the autosampler prior to analysis.
- Other observation, if any (e.g.: precipitation, color change etc.): None reported.
Buffers:
- Type and final molarity of buffer:
• pH 4 :
Potassium hydrogen phthalate: 0.005 mol dm^-3
• pH 7:
1. disodium hydrogen orthophosphate (anhydrous): 0.015 mol dm^-3
2. Potassium dihydrogen orthophosphate: 0.01 mol dm^-3
3. Sodium Chloride: 0.01 mol dm^-3
• pH 9 :
1. disodium tetraborate: 0.005 mol dm^-3
2. Sodium Chloride: 0.01 mol dm^-3
Details on test conditions:
TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: stoppered glass flasks
- Sterilisation method: The buffer solutions were filtered through a 0.2 µm membrane filter and subject to sonification and degassing. Thereby ensuring sterility of the test system.
- Lighting: Not applicable.
- Measures taken to avoid photolytic effects: All solutions shielded from light.
- Measures to exclude oxygen: Ultrasonication and degassing with nitrogen of buffer solutions.
- Details on test procedure for unstable compounds: Not applicable.
- Details of traps for volatile, if any: Not applicable (closed system)
- If no traps were used, is the test system closed/open: Closed system.
- Is there any indication of the test material adsorbing to the walls of the test apparatus?: Not reported.
TEST MEDIUM
- Volume used/treatment: Sample solutions were prepared in stoppered glass flasks at a nominal concentration of 2.5 x 10^-3 g/L in the three buffer solutions using a 1% tetrahydrofuran co-solvent.
- Kind and purity of water: Deionised or double distilled water.
- Preparation of test medium: The buffer solutions were filtered through a 0.2 µm membrane filter and subject to sonification and degassing. Thereby ensuring sterility of the test system. Sample solutions were prepared in stoppered glass flasks at a nominal concentration of 2.5 x 10^-3 g/L in the three buffer solutions using a 1% tetrahydrofuran co-solvent. Aliquots of the sample solutions were taken from the flasks at various times and the pH of each solution recorded.
- Renewal of test solution: No.
- Identity and concentration of co-solvent: 1% tetrahydrofuran
OTHER TEST CONDITIONS
- Adjustment of pH: No.
- Dissolved oxygen: Minimised.
Number of replicates:
None (single vessel, double injection).
Positive controls:
no
Negative controls:
no
Preliminary study:
In the preliminary test (tier 1) at 50 °C:
pH 4: greater than 50% hydrolysis was observed after 2.4 hours. Which is equivalent to a half-life < 1 day at 25 °C.
pH 7: Half-life of 20.8 hours. The extent of hydrolysis after 24 hours indicated a further test at 40 °C would be required to estimate the rate constant and half life.
pH 9: Half-life of 57.0 hours. The extent of hydrolysis after 92.5 hours indicated a further test at 40 °C would be required to estimate the rate constant and half life.
In the definitive test (tier 2) at 40 °C:
pH 7: Half-life of 141 hours.
pH 9: Half-life of 2070 hours.
The kinetics of the study were examined using the Arrhenius Plot Data to extrapolate the 25 °C kinetic and half-life information. As applicable.
Test performance:
No unusual findings were reported in the study.
Transformation products:
not measured
pH:
4
Temp.:
50 °C
DT50:
< 2.4 h
Type:
(pseudo-)first order (= half-life)
pH:
7
Temp.:
50 °C
Hydrolysis rate constant:
ca. 0.033 h-1
DT50:
ca. 20.8 h
Type:
(pseudo-)first order (= half-life)
pH:
9
Temp.:
50 °C
Hydrolysis rate constant:
ca. 0.012 h-1
DT50:
ca. 57 h
Type:
(pseudo-)first order (= half-life)
pH:
7
Temp.:
40 °C
Hydrolysis rate constant:
ca. 0.016 h-1
DT50:
ca. 43.1 h
Type:
(pseudo-)first order (= half-life)
pH:
9
Temp.:
40 °C
Hydrolysis rate constant:
ca. 0.003 h-1
DT50:
ca. 224 h
Type:
(pseudo-)first order (= half-life)
pH:
4
Temp.:
25 °C
DT50:
< 1 d
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: Arrhenius Plot Data: for determination to at 25°C
pH:
7
Temp.:
25 °C
Hydrolysis rate constant:
ca. 0.005 h-1
DT50:
ca. 5.86 d
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: Arrhenius Plot Data: for determination to at 25°C
pH:
9
Temp.:
25 °C
Hydrolysis rate constant:
ca. 0 h-1
DT50:
ca. 86.2 d
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: Arrhenius Plot Data: for determination to at 25°C
Details on results:
TEST CONDITIONS
- pH, sterility, temperature, and other experimental conditions maintained throughout the study: Yes. (No indications in the study of any anomoloies).Yes, by use of appropriate buffers however pH was not continuously monitored throughout the study, sterility was not examined.
- Anomalies or problems encountered (if yes): No.

MAJOR TRANSFORMATION PRODUCTS
Not examined.

MINOR TRANSFORMATION PRODUCTS
No examined.

MINERALISATION (distinguish between dark and irradiated samples)
Not examined.

INDICATION OF UNSTABLE TRANSFORMATION PRODUCTS:
Not examined.
VOLATILIZATION (at end of study)
Not examined.

UNIDENTIFIED RADIOACTIVITY (at end of study)
Not examined.

PATHWAYS OF HYDROLYSIS
Not examined.

SUPPLEMENTARY EXPERIMENT (if any): RESULTS:
In the preliminary test (tier 1) at 50 °C:
pH 4: greater than 50% hydrolysis was observed after 2.4 hours. Which is equivalent to a half-life < 1 day at 25 °C.
pH 7: Half-life of 20.8 hours. The extent of hydrolysis after 24 hours indicated a further test at 40 °C would be required to estimate the rate constant and half life.
pH 9: Half-life of 57.0 hours. The extent of hydrolysis after 92.5 hours indicated a further test at 40 °C would be required to estimate the rate constant and half life.
In the definitive test (tier 2) at 40 °C:
pH 7: Half-life of 141 hours.
pH 9: Half-life of 2070 hours.
The kinetics of the study were examined using the Arrhenius Plot Data to extrapolate the 25 °C kinetic and half-life information. As applicable.

The kinetics of the study were determined to be consistent with that of psuedo-first order reaction kinetics. The observed hydrolysis rate increases with decreasing pH (acidity).

Validation recovery samples were high > 90% and < 101%,

Validity criteria fulfilled:
yes
Remarks:
The study meets the tier 1 and tier 2 validity criteria. This is limited as detailed in 'Rationale for reliability incl. deficiencies'. The study is reliable as indicates that the substance is hydrolytically unstable under specific conditions.
Conclusions:
The substance was found to be unstable to hydrolysis in water at pH 5 (t1/2: < 1 day) and pH 7 (t1/2: < 1 week). The substance was found to be stable at pH 9 (t1/2: > 80 days).
Executive summary:

The test followed a method in accordance with EU Method C.7 (abiotic degradation: hydrolysis as a function of pH) under GLP serving as both a screening study (tier 1) and rate constant determination (tier 2) for the hydrolysis properties of the item. The study was conducted with the test vessels protected from light. The pH 4, 7 and 9 buffer solutions were filtered through a 0.2 µm membrane filter and subject to sonification and degassing. Thereby ensuring sterility of the test system. Sample solutions were prepared in stoppered glass flasks at a nominal concentration of 2.5 x 10^-3 g/L in the three buffer solutions using a 1% tetrahydrofuran co-solvent. In the preliminary test (tier 1) sampling was performed at a minimum: 0 hours, 2.4, 4, 6, 22.5, 24, 48, 74 and 92.5 hours (as appropriate depending on results). In the definitive test (tier 2) sampling was performed at a minimum: 0 hours, 43.3, 91.5, 92.0, 164, 211 hours.Aliquots of the sample solutions were taken from the flasks at various times and the pH of each solution recorded. The concentrations were determined by Gas Chromatography (GC). Duplicate aliquots (100 mL) of each sample were extracted with three portions (3 x 25 mL) of dichloromethane, each extract being filtered through anhydrous sodium sulphate. The combined extracts were evaporated to dryness and the residue re-dissolved in acetone (10 mL). For standards: Duplicate standard solutions of test material were prepared in acetone at a nominal concentration of 25 mg/L.Mean procedural recoveries were pH 4: 90.3%, pH 7: 99.3% and pH 9: 101% and therefore the analytical system was validated. In the preliminary test (tier 1) at 50 °C at pH 4: greater than 50% hydrolysis was observed after 2.4 hours. Which is equivalent to a half-life < 1 day at 25 °C. At pH 7: Half-life of 20.8 hours. At pH 9: Half-life of 57.0 hours. The extent of hydrolysis at pH 7 and 9 indicated a further test at 40 °C would be required to estimate the rate constant and half-lives. Therefore in the definitive test (tier 2) at 40 °C: at pH 7 the Half-life of 141 hours was determined. At pH 9: Half-life of 2070 hours was determined. Using Arrhenius plots, the estimated rate constants and pseudo-first order (DT50) rate constants were: pH 4: (not determined) and half-life < 1 day. At pH 7: 1.37x10^-6 per second and half-life of 5.86 days. At pH 9: 9x31x10^-8 per second and half life of 86.2 days. Validation of recovery of analysis of the sample procedure was carried out and proved adequate for the test.

Description of key information

Hydrolysis: half-life for hydrolysis: pH 4: t1/2: < 1 day ; pH 7: t1/2: 5.86 days; pH 9: t1/2: 86.2 days, at 25 °C, 1 atm, EU Method C.7, 2002

Key value for chemical safety assessment

Additional information

Key data: EU Method C.7 , 2002: The test followed a method in accordance with EU Method C.7 (abiotic degradation: hydrolysis as a function of pH) under GLP serving as both a screening study (tier 1) and rate constant determination (tier 2) for the hydrolysis properties of the item. The study was conducted with the test vessels protected from light. The pH 4, 7 and 9 buffer solutions were filtered through a 0.2 µm membrane filter and subject to sonification and degassing. Thereby ensuring sterility of the test system. Sample solutions were prepared in stoppered glass flasks at a nominal concentration of 2.5 x 10^-3 g/L in the three buffer solutions using a 1% tetrahydrofuran co-solvent. In the preliminary test (tier 1) sampling was performed at a minimum: 0 hours, 2.4, 4, 6, 22.5, 24, 48, 74 and 92.5 hours (as appropriate depending on results). In the definitive test (tier 2) sampling was performed at a minimum: 0 hours, 43.3, 91.5, 92.0, 164, 211 hours.Aliquots of the sample solutions were taken from the flasks at various times and the pH of each solution recorded. The concentrations were determined by Gas Chromatography (GC). Duplicate aliquots (100 mL) of each sample were extracted with three portions (3 x 25 mL) of dichloromethane, each extract being filtered through anhydrous sodium sulphate. The combined extracts were evaporated to dryness and the residue re-dissolved in acetone (10 mL). For standards: Duplicate standard solutions of test material were prepared in acetone at a nominal concentration of 25 mg/L.Mean procedural recoveries were pH 4: 90.3%, pH 7: 99.3% and pH 9: 101% and therefore the analytical system was validated. In the preliminary test (tier 1) at 50 °C at pH 4: greater than 50% hydrolysis was observed after 2.4 hours. Which is equivalent to a half-life < 1 day at 25 °C. At pH 7: Half-life of 20.8 hours. At pH 9: Half-life of 57.0 hours. The extent of hydrolysis at pH 7 and 9 indicated a further test at 40 °C would be required to estimate the rate constant and half-lives. Therefore in the definitive test (tier 2) at 40 °C: at pH 7 the Half-life of 141 hours was determined. At pH 9: Half-life of 2070 hours was determined. Using Arrhenius plots, the estimated rate constants and pseudo-first order (DT50) rate constants were: pH 4: (not determined) and half-life < 1 day. At pH 7: 1.37x10^-6 per second and half-life of 5.86 days. At pH 9: 9x31x10^-8 per second and half life of 86.2 days. Validation of recovery of analysis of the sample procedure was carried out and proved adequate for the test.

 

Weight of Evidence: conclusion:

The substance can rapidly hydrolytically degrade under acidic (pH 4) conditions with a half-life of less than 1 day. Under neutral conditions (pH 7) the test item is unstable and can degrade with a half-life of 5.86 days. The substance is hydrolytically stable at basic (pH 9) conditions with a half-life of > 80 days.