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Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Experiment start date - 17 February 2005; Experiment completion date - 25 April 2005; Study completion date - 21 June 2006.

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

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Identity: FAT 40819/A
Description: Red brown powder
Batch number: Red ROE 420 BOP 01/04
Purity: approx. 77 %
Stability of test item: Stable under storage condition
Expiry date: 02 November 2009
Stability of test item dilution: Stable in PEG 300 for at least 7 days at room temperature
Storage conditions: At room temperature.

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

Before and after incubation, 10 µL aliquots of the test solutions at each pH value were analysed without dilution by measuring the UV signal of FAT 40819/A after HPLC separation of the injected sample solution.

Buffers:

Buffer pH 4: Biphthalate
Buffer pH 7: Phosphate
Buffer pH 9: Borate

The buffer solutions were sterilized for 25 minutes in an autoclave prior to first use. Nitrogen was passed through the buffer solutions for about 5 minutes except when freshly sterilized.

Estimation method (if used):

The rate constants at 25 °C are calculated using the Arrhenius equation.

Details on test conditions:

GENERAL PROCEDURE:
A preliminary hydrolysis test was performed at 50.0 ± 0.1 °C at pH 4.0, pH 7.0 and pH 9.0, each. Aliquots of each test solution were analysed at the beginning and after 2.4 and 120 hours using the analytical method as described later in this report. Due to the instability of the test item found in the preliminary test at 50.0 °C, further hydrolysis tests were performed at 70 °C and 80 °C in the buffered test solution at pH 4.0 and at 50 °C, 70 °C and 80 °C in the buffered test solution at pH 9.0. At pH 7.0 the test item was found to be stable at 50 °C. Therefore, no further testing was performed at this pH-value.

PREPARATION OF TEST SOLUTIONS:
Hydrolysis at 50 °C:
- pH 4.0, Preliminary and Main Test: 9.99 mg of FAT 40819/A were dissolved in 100 mL buffer solution (pH 4.0) to prepare a test solution of 99.9 µg/mL. Two aliquots of this test solution of approximately 50 mL each were transferred into 50 mL Erlenmeyer flasks in order to perform a duplicate test. To reduce the oxygen in the solution, nitrogen was passed through for 5 minutes.
- pH 7.0, Preliminary Test: 9.72 mg of FAT 40819/A were dissolved in 100 mL buffer solution (pH 7.0) to prepare a test solution of 97.2 µg/mL. Two aliquots of this test solution of approximately 50 mL each were transferred into 50 mL Erlenmeyer flasks in order to perform a duplicate test. To reduce the oxygen in the solution, nitrogen was passed through for 5 minutes.
- pH 9.0, Preliminary Test: 11.02 mg of FAT 40819/A were dissolved in 100 mL buffer solution (pH 9.0) to prepare a test solution of 110.2 µg/mL. Two aliquots of this test solution of approximately 50 mL each were transferred into 50 mL Erlenmeyer flasks in order to perform a duplicate test. To reduce the oxygen in the solution, nitrogen was passed through for 5 minutes.
- pH 9.0, Main Test: 11.57 mg of FAT 40819/A were dissolved in 100 mL buffer solution (pH 9.0) to prepare a test solution of 115.7 µg/mL. Two aliquots of this test solution of approximately 50 mL each were transferred into 50 mL Erlenmeyer flasks in order to perform a duplicate test. To reduce the oxygen in the solution, nitrogen was passed through for 5 minutes.

Hydrolysis at 70 °C:
- pH 4.0, Main Test: 10.99 mg of FAT 40819/A were dissolved in 100 mL buffer solution (pH 4.0) to prepare a test solution of 109.9 µg/mL. Two aliquots of this test solution of approximately 50 mL each were transferred into 50 mL Erlenmeyer flasks in order to perform a duplicate test. To reduce the oxygen in the solution, nitrogen was passed through for 5 minutes.
- pH 9.0, Main Test: 10.01 mg of FAT 40819/A were dissolved in 100 mL buffer solution (pH 9.0) to prepare a test solution of 100.1 µg/mL. Two aliquots of this test solution of approximately 50 mL each were transferred into 50 mL Erlenmeyer flasks in order to perform a duplicate test. To reduce the oxygen in the solution, nitrogen was passed through for 5 minutes.

Hydrolysis at 80 °C:
- pH 4.0, Main Test: 11.38 mg of FAT 40819/A were dissolved in 100 mL buffer solution (pH 4.0) to prepare a test solution of 113.8 µg/mL. Two aliquots of this test solution of approximately 50 mL each were transferred into 50 mL Erlenmeyer flasks in order to perform a duplicate test. To reduce the oxygen in the solution, nitrogen was passed through for 5 minutes.
- pH 9.0, Main Test: 10.04 mg of FAT 40819/A were dissolved in 100 mL buffer solution (pH 9.0) to prepare a test solution of 100.4 µg/mL. Two aliquots of this test solution of approximately 50 mL each were transferred into 50 mL Erlenmeyer flasks in order to perform a duplicate test. To reduce the oxygen in the solution, nitrogen was passed through for 5 minutes.

Duration:

600 h

pH:

4

Temp.:

50 °C

Initial conc. measured:

> 95.5 - < 95.8 mg/L

Duration:

102.8 h

pH:

4

Temp.:

70 °C

Initial conc. measured:

> 108.3 - < 110.6 mg/L

Duration:

62 h

pH:

4

Temp.:

80 °C

Initial conc. measured:

> 106.1 - < 107.4 mg/L

Duration:

167.6 h

pH:

9

Temp.:

50 °C

Initial conc. measured:

> 115.4 - < 121.6 mg/L

Duration:

11.2 h

pH:

9

Temp.:

70 °C

Initial conc. measured:

> 98.2 mg/L

Duration:

5.5 h

pH:

9

Temp.:

80 °C

Initial conc. measured:

> 97.7 - < 97.9 mg/L

Number of replicates:

2

Preliminary study:

The hydrolysis preliminary test was performed with FAT 40819/A at 50.0 °C ± 0.1 °C at each of pH 4.0, pH 7.0, and pH 9.0 in duplicate. The test solutions of FAT 40819/A were thermostated to 50.0 °C and analysed in time intervals.
- pH 4.0: The results of the preliminary test show, that FAT 40819/A is not stable at pH 4. Therefore, the test at 50°C was prolonged to the range of 20 % to 70 % degradation. The half-life time of FAT 40819/A at 50.0°C and pH 4.0 was calculated to be 370 hours (15 days).
- pH 7.0: The results of pH 7.0 showed no significant degradation of FAT 40819/A at 50 °C. According to the EEC Directive 92/69, Section C.7, it can be concluded, that the estimated half-life time is higher than one year under representative environmental conditions (25 °C). Therefore, FAT 40819/A can be considered to be hydrolytically stable at pH 7.0 and no further testing was necessary at this pH-value.
- pH 9.0: The results of the preliminary test show, that FAT 40819/A is not stable at pH 9. Therefore, the test at 50 °C was repeated in the range of 20 % to 70 % degradation. The half-life time of FAT 40819/A at 50.0 °C and pH 9.0 was calculated to be 116 hours (5 days).

Transformation products:

not measured

pH:

4

Temp.:

25 °C

Hydrolysis rate constant:

0 h-1

DT50:

3 912 h

Type:

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

Remarks on result:

other: as calculated with the Arrhenius equation

pH:

4

Temp.:

50 °C

Hydrolysis rate constant:

0.002 h-1

DT50:

370 h

Type:

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

pH:

4

Temp.:

70 °C

Hydrolysis rate constant:

0.01 h-1

DT50:

69 h

Type:

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

pH:

4

Temp.:

80 °C

Hydrolysis rate constant:

0.02 h-1

DT50:

34 h

Type:

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

pH:

9

Temp.:

25 °C

Hydrolysis rate constant:

0 h-1

DT50:

4 704 h

Type:

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

Remarks on result:

other: as calculated with the Arrhenius equation

pH:

9

Temp.:

50 °C

Hydrolysis rate constant:

0.006 h-1

DT50:

116 h

Type:

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

pH:

9

Temp.:

70 °C

Hydrolysis rate constant:

0.078 h-1

DT50:

9 h

Type:

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

pH:

9

Temp.:

80 °C

Hydrolysis rate constant:

0.258 h-1

DT50:

3 h

Type:

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

Validity criteria fulfilled:

yes

Conclusions:

The test substance is stable at pH 7.0. Its calculated half-life time is longer than one year at 25 °C.
The test substance at pH 4.0 has a calculated half-life time of 3912 hours (163 days) at 25 °C.
The test substance at pH 9.0 has a calculated half-life time of 4704 hours (196 days) at 25 °C.

Executive summary:

A GLP-compliant hydrolysis test was performed according to OECD guideline 111 and EEC Directive 92/59, C.7. The hydrolysis of the test item was performed at 50.0 ± 0.1 °C at each of pH 4.0, pH 7.0 and pH 9.0. The test substance was found to be stable at pH 7.0 and 50 °C. Therefore, no further testing was performed at this pH-value. The test substance was not stable at pH 4.0 and at pH 9.0, further testing was performed at elevated temperatures in order to calculate the rate constant and the half-life time of the hydrolysis at pH 4.0, pH 9.0 at 25 °C. In conclusion, The test substance is stable at pH 7.0. Its half-life time is longer than one year at 25 °C. The test substance at pH 4.0 has a half-life time of 3912 hours (163 days) at 25 °C. The test substance at pH 9.0 has a half-life time of 4704 hours (196 days) at 25 °C.

Description of key information

The test substance is hydrolytically stable under environmental conditions.

Key value for chemical safety assessment

Half-life for hydrolysis:

1 yr

at the temperature of:

25 °C

Additional information

A GLP-compliant hydrolysis test was performed according to OECD guideline 111 and EEC Directive 92/59, C.7. The hydrolysis of the test item was performed at 50.0 ± 0.1 °C at each of pH 4.0, pH 7.0 and pH 9.0. The test substance was found to be stable at pH 7.0 and 50 °C. Therefore, no further testing was performed at this pH-value. The test substance was not stable at pH 4.0 and at pH 9.0, further testing was performed at elevated temperatures in order to calculate the rate constant and the half-life time of the hydrolysis at pH 4.0, pH 9.0 at 25 °C. In conclusion, the test substance is stable at pH 7.0. Its half-life time is longer than one year at 25 °C. The test substance at pH 4.0 has a half-life time of 3912 hours (163 days) at 25 °C. The test substance at pH 9.0 has a half-life time of 4704 hours (196 days) at 25 °C.