Cyclopropanecarboxylic acid, 2-[1-(3,3-dimethylcyclohexyl)ethoxy]-2-methylpropyl ester

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

26-08-2005 to 26-10-2005

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 stable 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

Guideline:

EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)

Deviations:

no

Qualifier:

equivalent or similar to guideline

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. QA statement)

Remarks:

inspected: February 2005 ; signature: May 2005

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

- Sampling intervals for the parent/transformation products:
Preliminary test (tier 1): 0 hours, 24, 48, 54, 72, 96 and 120 hours (as appropriate depending on results).
Definitive test (tier 2): In both the tier 1 and tier 2 testing other time periods may have been measured (recorded in the primary data and full study report). This included pH 4: 0, 67, 73, 91, 139, 163, 235.5, 259 hours. pH 7.0: 0, 19, 23, 43, 50, 67, 73 hours and 141 hours (as applicable) and pH 9: 0, 1.5, 2, 3, 4, 5.5, 6, 7.5, 18, 19, 20, 22 hours (as applicable)
- Sampling method: Test samples were analyzed by single injection. No pretreatment. 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). 6 mL or 9 mL was transferred to a 20 mL vial thereafter the relevant sample buffer solution and 1.5 ml internal standard solution was added. Each vial was closed and shaken by hand for 30 seconds. The cyclohexane layer (upper layer) was injected into the GC system.
- 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 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:

- pH: 4
- Type and final molarity of buffer: Acetate buffer pH 4, 0.05 M
- Composition of buffer: sodium acetate/acetic acid/Milli-Q water.
- pH: 7
- Type and final molarity of buffer: Phosphate buffer pH 7, 0.05 M
- Composition of buffer: potassium dihydrogen phosphate/sodium hydroxide/Milli-Q water.
- pH: 9
- Type and final molarity of buffer: borate buffer pH 7, 0.05 M
- Composition of buffer: boric acid/potassium chloride/sodium hydroxide/Milli-Q water.

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 FP 30/0.2 CA-S filter and subject to degassing, to exclude oxygen, nitrogen gas was purged through the solution for 5 minutes. Thereby ensuring sterility of the test system.
- Lighting: Not applicable.
- Measures taken to avoid photolytic effects: All solutions were placed in the dark.
- Measures to exclude oxygen: Degassing with nitrogen gas for 5 minutes. Closed vessels.
- 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: For each sampling time, duplicate sterile vessels under vacuum were filled with 50 mL or 200 mL (definitive test) test solution and placed in the dark in a temperature controlled environment.
- Kind and purity of water: Milli-Q RO Water
- Preparation of test medium: The buffer solutions were filter-sterilised through a 0.2 µm FP 30/0.2 CA-S filter 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 71 microlitre at 704 mg/L in acetone (preliminary test at pH4, pH 7 and pH 9) or 81 microlitre at 820 mg/L in acetone (pH 4) or 0.25 mg/L (definitive test) using a spiking solutions in acetone. For each sampling time, duplicate sterile vessels under vacuum were filled and placed in the dark in a temperature-controlled environment. Nominal concentrations were corrected for the spiking volume.
- Renewal of test solution: No.
- Identity and concentration of co-solvent: Acetone. For further information see above.

OTHER TEST CONDITIONS
- Adjustment of pH: No.
- Dissolved oxygen: Minimised.

Duration:

5 d

pH:

4

Temp.:

50 °C

Initial conc. measured:

0.65 mg/L

Remarks:

Preliminary test 1

Duration:

5 d

pH:

7

Temp.:

50 °C

Initial conc. measured:

0.694 mg/L

Remarks:

Preliminary test 1

Duration:

5 d

pH:

9

Temp.:

50 °C

Initial conc. measured:

0.744 mg/L

Remarks:

Preliminary test 1

Duration:

5 d

pH:

4

Temp.:

50 °C

Initial conc. measured:

0.203 mg/L

Remarks:

Preliminary test 2

Duration:

259 h

pH:

4

Temp.:

90 °C

Initial conc. measured:

0.219 mg/L

Remarks:

Definitive Test 1

Duration:

141 h

pH:

7

Temp.:

75 °C

Initial conc. measured:

0.26 mg/L

Remarks:

Definitive Test 2

Duration:

73 h

pH:

7

Temp.:

90 °C

Initial conc. measured:

0.261 mg/L

Remarks:

Definitive Test 3

Duration:

22 h

pH:

9

Temp.:

75 °C

Initial conc. measured:

0.234 mg/L

Remarks:

Definitive Test 4

Duration:

7.5 h

pH:

9

Temp.:

75 °C

Initial conc. measured:

0.207 mg/L

Remarks:

Definitive Test 5

Duration:

7 h

pH:

9

Temp.:

90 °C

Initial conc. measured:

0.207 mg/L

Remarks:

Definitive Test 6

Number of replicates:

None (duplicate or triplicate vessels, single injection).

Positive controls:

no

Negative controls:

no

Preliminary study:

In the preliminary test (tier 1) at 50 °C:
pH 4: at 5 days the relative concentration of the test item was measured at 84%.
pH 7: at 5 days the relative concentration of the test item was measured at 58%
pH 9: at 5 days the relative concentration of the test item was measured at 38%
At each pH, a sharp initial decrease in test substance concentration was observed, because this decrease was not expected to be due to hydrolysis, it was decided to perform subsequent tests at a lower test substance concentration and to use separate vessels for each sampling point. lt was decided to perform main studies at pH 7 and 9, because a decrease > 10 % was observed in the time period between 2.4 hours and 5 days of incubation and to repeat the preliminary test at pH 4 (no decrease observed between 2.4 hours and 5 days of incubation).

In the preliminary test (tier 1) part 2 at 50 °C:
pH 4: at 5 days the relative concentration of the test item was measured at 75%.

Test performance:

IIn the definitive test (tier 2) at 75 °C and 90 °C:
For testing of pseudo-first order kinetics at pH 4, pH 7 and pH 9, the logarithms of the relative concentrations between 80% and 30% (i.e. between 20% and 70% hydrolysis) were plotted against time. Because at all pH conditions linear relationships were found, the reactions were considered to be (pseudo)-first order. Hence, the half-life times at 25°C were estimated in a subsequent test.

Transformation products:

not measured

pH:

4

Temp.:

89.5 °C

Hydrolysis rate constant:

0.003 h-1

DT50:

276 h

Type:

(pseudo-)first order (= half-life)

pH:

4

Temp.:

79.5 °C

Hydrolysis rate constant:

0.001 h-1

DT50:

552 h

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other: Predicted rate constant and half-life time

pH:

4

Temp.:

25 °C

Hydrolysis rate constant:

0 h-1

DT50:

54 618 h

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other: Predicted rate constant and half-life time

pH:

7

Temp.:

89.7 °C

Hydrolysis rate constant:

0.007 h-1

DT50:

92.7 h

Type:

(pseudo-)first order (= half-life)

pH:

7

Temp.:

75 °C

Hydrolysis rate constant:

0.002 h-1

DT50:

212 h

Type:

(pseudo-)first order (= half-life)

pH:

7

Temp.:

25 °C

Hydrolysis rate constant:

0 h-1

DT50:

7 104 h

Type:

(pseudo-)first order (= half-life)

pH:

9

Temp.:

89.2 °C

Hydrolysis rate constant:

0.149 h-1

DT50:

4.65 h

Type:

(pseudo-)first order (= half-life)

pH:

9

Temp.:

75.3 °C

Hydrolysis rate constant:

0.053 h-1

DT50:

13.1 h

Type:

(pseudo-)first order (= half-life)

pH:

9

Temp.:

25 °C

Hydrolysis rate constant:

0.001 h-1

DT50:

1 226 h

Type:

(pseudo-)first order (= half-life)

Other kinetic parameters:

For pH 4, the rate constant and the corresponding half-life time at 25°C could not be calculated since only the rate constant at one temperature was known. From the results at 90°C it could be concluded that hydrolysis at pH 4 is very slow. Based on the general rule that the reaction rates of chemical reactions increase 2-3 times when the temperature is increased with 10°C (Q10), one can predict the rate constant and half-life time of test item at 25°C, using the data obtained at pH 4 and 89.5°C. Assuming a Q10 of 2 (Le. the worst case situation), a half-life time of > 6 years was calculated. This is presented as predicted rate constants and half life.

At pH 7 and 9, Q10 of 1.78 and 2.10 were determined. Indicating that a Q10 of 2 is a good estimate for the temperature dependence of the degradation of test item. Prediction based on a Q10 of 1.78 would still give a half-life time of 2.5 years at 25°C.

Therefore it was concluded that the pH 9 at 25°C half life was > 1 year.

Details on results:

TEST CONDITIONS
- pH, sterility, temperature, and other experimental conditions maintained throughout the study: Yes. (no indications in the study of any anomalies).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): Where encountered additional preliminary testing and/or appropriate definitive testing was conducted. Prediction modelling was also employed.

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: See above.

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'.

Conclusions:

The substance was found to be hydrolytically stable to hydrolysis in water at 25°C : pH 4 and (t1/2: > 1 year). The substance was found to be unstable to hydrolysis in water at 25°C and pH 7 (t1/2: 7104 hours) and pH 9 (t1/2: 1226 hours).

Executive summary:

The test followed a method in accordance with EU Method C.7 for abiotic degradation: hydrolysis as a function of pH under GLP. The study served as both a preliminary screening study (tier 1) and rate constant determination (tier 2) for the hydrolysis properties of the item, where applicable. 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 degassing. Thereby ensuring sterility of the test system. The test item was dispersed into the buffer solutions using acetone co-solvent. Aliquots of the sample solutions were taken from the flasks at various times and the pH of each solution recorded at the beginning and end of the study as applicable. The concentrations were determined by Gas Chromatography (GC). In the preliminary test, at each pH, a sharp initial decrease in test substance concentration was observed, because this decrease was not expected to be due to hydrolysis, it was decided to perform subsequent tests at a lower test substance concentration and to use separate vessels for each sampling point. lt was decided to perform main studies at pH 7 and 9, because a decrease > 10 % was observed in the time period between 2.4 hours and 5 days of incubation and to repeat the preliminary test at pH 4 (no decrease observed between 2.4 hours and 5 days of incubation). In the definitive test (tier 2) at 75 °C and 90 °C: for testing of pseudo-first order kinetics at pH 4, pH 7 and pH 9, the logarithms of the relative concentrations between 80% and 30% (i.e. between 20% and 70% hydrolysis) were plotted against time. Because at all pH conditions linear relationships were found, the reactions were considered to be (pseudo)-first order. Hence, the half-life times at 25°C were estimated in a subsequent test. For pH 4, the rate constant and the corresponding half-life time at 25°C could not be calculated since only the rate constant at one temperature was known. From the results at 90°C it could be concluded that hydrolysis at pH 4 is very slow. Based on the general rule that the reaction rates of chemical reactions increase 2-3 times when the temperature is increased with 10°C (Q10), one can predict the rate constant and half-life time of test item at 25°C, using the data obtained at pH 4 and 89.5°C. Assuming a Q10 of 2 (Le. the worst case situation), a half-life time of > 6 years was calculated. This is presented as predicted rate constants and half life at this pH. Comparison with the other data at other pH supplemented the prediction. The substance was found to be hydrolytically stable to hydrolysis in water at 25°C : pH 4 and (t1/2: > 1 year). The substance was found to be unstable to hydrolysis in water at 25°C and pH 7 (t1/2: 7104 hours) and pH 9 (t1/2: 1226 hours).

Description of key information

Hydrolysis: half-life for hydrolysis at 25 °C : pH 4 : t1/2: > 1 year ; pH 7: t1/2: 7104 hours; pH 9: t1/2: 1226 hours, 1 atm, EU Method C.7, 2006

(pseudo-)first order rate constants at 25 °C :

pH 4 (predicted) : 0.0000127 h-1

pH 7 (measured) : 0.0000976 h-1

pH 9 (measured) : 0.000565 h-1

Key value for chemical safety assessment

Half-life for hydrolysis:

7 104 h

at the temperature of:

25 °C

Additional information

Key study : EU Method C.7 , 2006 : The test followed a method in accordance with EU Method C.7 for abiotic degradation: hydrolysis as a function of pH under GLP. The study served as both a preliminary screening study (tier 1) and rate constant determination (tier 2) for the hydrolysis properties of the item, where applicable. 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 degassing. Thereby ensuring sterility of the test system. The test item was dispersed into the buffer solutions using acetone co-solvent. Aliquots of the sample solutions were taken from the flasks at various times and the pH of each solution recorded at the beginning and end of the study as applicable. The concentrations were determined by Gas Chromatography (GC). In the preliminary test, at each pH, a sharp initial decrease in test substance concentration was observed, because this decrease was not expected to be due to hydrolysis, it was decided to perform subsequent tests at a lower test substance concentration and to use separate vessels for each sampling point. lt was decided to perform main studies at pH 7 and 9, because a decrease > 10 % was observed in the time period between 2.4 hours and 5 days of incubation and to repeat the preliminary test at pH 4 (no decrease observed between 2.4 hours and 5 days of incubation). In the definitive test (tier 2) at 75 °C and 90 °C: for testing of pseudo-first order kinetics at pH 4, pH 7 and pH 9, the logarithms of the relative concentrations between 80% and 30% (i.e. between 20% and 70% hydrolysis) were plotted against time. Because at all pH conditions linear relationships were found, the reactions were considered to be (pseudo)-first order. Hence, the half-life times at 25°C were estimated in a subsequent test. For pH 4, the rate constant and the corresponding half-life time at 25°C could not be calculated since only the rate constant at one temperature was known. From the results at 90°C it could be concluded that hydrolysis at pH 4 is very slow. Based on the general rule that the reaction rates of chemical reactions increase 2-3 times when the temperature is increased with 10°C (Q10), one can predict the rate constant and half-life time of test item at 25°C, using the data obtained at pH 4 and 89.5°C. Assuming a Q10 of 2 (Le. the worst case situation), a half-life time of > 6 years was calculated. This is presented as predicted rate constants and half life at this pH. Comparison with the other data at other pH supplemented the prediction. The substance was found to be hydrolytically stable to hydrolysis in water at 25°C : pH 4 and (t1/2: > 1 year). The substance was found to be unstable to hydrolysis in water at 25°C and pH 7 (t1/2: 7104 hours) and pH 9 (t1/2: 1226 hours).