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Hydrolysis

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Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Experiment start date - 16 July 2003; Experiment completion date - 30 July 2003; Study completion date - 22 September 2003.
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 40812/A
Batch: WP 8/03
Purity: approx. 75 %
Appearance: Solid, dark red-brownish powder
Expiration date: 23 April 2010
Storage: At room temperature at about 20 °C
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
After incubation, 10 µL aliquots of the test solutions at each pH value were analysed without dilution by measuring the UV signal of FAT 40'812/A after HPLC separation of the injected sample solution.
Buffers:
Buffer pH 4: Biphthalate: Baker Art. No. 5657
Buffer pH 7: Phosphate: Baker Art. No. 5656
Buffer pH 9: Borate: Baker Art. No. 7145

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 constant at 25 °C is estimated by the use of the Arrhenius relationship.
Details on test conditions:
General Procedure:
A preliminary hydrolysis test was performed at 50.0°C ± 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. At pH 4.0, the test item was found to be stable at 50°C. Therefore, no further testing was performed at this pH. Due to the instability of the test item observed during the preliminary test at 50°C at pH 7.0, further hydrolysis tests were performed at 50°C, 60°C and 70°C in the buffered test solutions. At pH 9.0, the test item was found to be very unstable at 50°C. Therefore, no further testing was performed at this pH.

PREPARATION OF TEST SOLUTIONS
Hydrolysis at 50°C:
- pH 4.0: A 8.63 mg sample of FAT40812/A was dissolved in 100 mL buffer solution (pH 4.0) to prepare a test solution of 86.3 µg/mL. Two aliquots from the test solution, approximately 50 mL each were transferred into 50 mL Erlenmeyer flasks in order to perform a duplicate test.
- pH 7.0, Preliminary Test: A 9.53 mg sample of FAT40812/A was dissolved in 100 mL buffer solution (pH 7.0) to prepare a test solution of 95.3 µg/mL. Two aliquots from the test solution, approximately 50 mL each were transferred into 50 mL Erlenmeyer flasks in order to perform a duplicate test.
- pH 7.0, Main Test: A 8.86 mg sample of FAT40812/A was dissolved in 100 mL buffer solution (pH 7.0) to prepare a test solution of 88.6 µg/mL. Two aliquots from the test solution, approximately 50 mL each were transferred into 50 mL Erlenmeyer flasks in order to perform a duplicate test.
- pH 9.0: A 9.86 mg sample of FAT40812/A was dissolved in 100 mL buffer solution (pH 9.0) to prepare a test solution of 98.6 µg/mL. Two aliquots from the test solution, approximately 50 mL each were transferred into 50 mL Erlenmeyer flasks in order to perform a duplicate test.

Hydrolysis at 60 °C:
- pH 7.0: A 10.16 mg sample of FAT40812/A was dissolved in 100 mL buffer solution (pH 7.0) to prepare a test solution of 101.6 µg/mL. Two aliquots from the test solution, approximately 50 mL each were transferred into 50 mL Erlenmeyer flasks in order to perform a duplicate test.

Hydrolysis at 70 °C
- pH 7.0: A 12.10 mg sample of FAT40812/A was dissolved in 100 mL buffer solution (pH 7.0) to prepare a test solution of 121.0 µg/mL. Two aliquots from the test solution, approximately 50 mL each were transferred into 50 mL Erlenmeyer flasks in order to perform a duplicate test.
Duration:
8.5 h
pH:
7
Temp.:
50
Initial conc. measured:
> 91.1 - < 91.5 mg/L
Duration:
2.5 h
pH:
7
Temp.:
60
Initial conc. measured:
> 97.9 - < 98.1 mg/L
Duration:
1 h
pH:
7
Temp.:
70
Initial conc. measured:
> 116.8 - < 117.8 mg/L
Number of replicates:
2
Preliminary study:
The hydrolysis preliminary test was performed with FAT 40812A 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 40812/A were tempered to 50.0 °C and analysed in time intervals.
- pH 4.0: The results of pH 4.0 showed no significant degradation for both components of FAT 40812/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 40812/A can be considered to be hydrolytically stable at pH 4.0, and no further testing was necessary at this pH.
- pH 7.0: The results of the preliminary test show, that FAT 40812/A is not stable at pH 7. Therefore, the test was repeated at 50 °C in the range of 20 % to 70 % degradation.
- pH 9.0: The results of pH 9.0 show that FAT 40812/A is very unstable at 50 °C. The degradation of FAT 40812/A at pH 9.0 was determined to be >50 % after 2.4 hours of incubation. The analytical results indicate that at pH 9.0, FAT 40812/A already starts to hydrolyse immediately after being dissolved in the buffer solution. According to the EEG Directive 92/69, Section C.7, it can be concluded, that the estimated half-life time at pH 9.0 is shorter than one day under representative environmental conditions (25 °C). Therefore, no further testing was necessary at this pH.
Transformation products:
not measured
pH:
7
Temp.:
25 °C
Hydrolysis rate constant:
0.003 h-1
DT50:
212 h
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: as calculated using the Arrhenius equation.
pH:
7
Temp.:
50 °C
Hydrolysis rate constant:
0.102 h-1
DT50:
7 h
Type:
(pseudo-)first order (= half-life)
pH:
7
Temp.:
60 °C
Hydrolysis rate constant:
0.441 h-1
DT50:
2 h
Type:
(pseudo-)first order (= half-life)
pH:
7
Temp.:
70 °C
Hydrolysis rate constant:
1.16 h-1
DT50:
1 h
Type:
(pseudo-)first order (= half-life)
Validity criteria fulfilled:
yes
Conclusions:
The test substance is stable at pH 4.0. Its half-life time is longer than one year at 25 °C. The test substance at pH 7.0 has a half-life time of 212 hours (9 days) at 25 °C. The test substance is unstable at pH 9.0. Its half-life time is shorter than one day at 25 °C.
Executive summary:

A GLP-compliant hydrolysis test was performed according to OECD guideline 111. 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 4.0 at 50 °C. Therefore, no further testing was performed at this pH-value. The test substance was not stable at pH 7.0 and further testing was performed at elevated temperatures in order to calculate the rate constant and the half-life time of the hydrolysis at 25 °C (by means of the Arrhenius equation). At pH 9.0, the test substance was very unstable at 50 °C.  Therefore, no further testing was performed at this pH. In conclusion, The test substance is stable at pH 4.0. Its half-life time is longer than one year at 25 °C. The test substance at pH 7.0 has a half-life time of 212 hours at 25 °C. The test substance at pH 9.0 has a half-life time shorter than one day at 25 °C.

Description of key information

The test substance is stable at pH 4.0. Its half-life time is longer than one year at 25 °C. The test substance at pH 7.0 has a half-life time of 212 hours at 25 °C. The test substance at pH 9.0 has a half-life time shorter than one day at 25 °C.

Key value for chemical safety assessment

Half-life for hydrolysis:
212 h
at the temperature of:
25 °C

Additional information

A GLP-compliant hydrolysis test was performed according to OECD guideline 111. 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 4.0 at 50 °C. Therefore, no further testing was performed at this pH-value. The test substance was not stable at pH 7.0 and further testing was performed at elevated temperatures in order to calculate the rate constant and the half-life time of the hydrolysis at 25 °C (by means of the Arrhenius equation). At pH 9.0, the test substance was very unstable at 50°C. Therefore, no further testing was performed at this pH. In conclusion, the test substance is stable at pH 4.0. Its half-life time is longer than one year at 25 °C. At pH 7.0 the test substance has a half-life time of 212 hours at 25 °C. At pH 9.0 it has a half-life time shorter than one day at 25 °C.

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