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Environmental fate & pathways

Hydrolysis

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Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Nov. 08, 1996 to Feb. 20, 1997
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Deviations:
no
Qualifier:
according to
Guideline:
other: EC Guideline C.7 (Official Journal of the European Communities L 383 A), 1992
GLP compliance:
yes (incl. certificate)
Remarks:
Swiss GLP
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: WP 2/96
- Expiration date of the lot/batch: November, 2004

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: The test substance can be stored at room temperature
Radiolabelling:
not specified
Analytical monitoring:
yes
Buffers:
pH 4.0: Ciba-Geigy Code No. P07: 0.1 mole acetic add + 0.1 mole sodium acetate diluted to 1000 ml with water + 60.0 ml 1.0 N HCI.
pH 7.0: Ciba-Geigy Code No, P10: 0.041 mole disodium hydrogen phosphate + 0.028 mole potassium dihydrogen phosphate diluted to 1000 ml with water,
pH 9.0: Ciba-Geigy Code No, P12: 0,043 mole disodium tetraborate + 0.017 mole potassium dihydrogen phosphate diluted to 1000 ml with water.
Details on test conditions:
300.0 to 330.0 mg test substance were dissolved and diluted to 100.0 ml with water. 10.0 ml of this solution were pipetted into a 100 ml measuring flask, which was then filled up to the mark with the respective buffer solution.
Calibration solutions: Three different calibration solutions were prepared (immediately before use), which had approximately the same concentrations of acid and alkali, respectively, and buffer as the corresponding test solutions.
Duration:
59.6 h
pH:
4
Temp.:
80 °C
Duration:
113.4 h
pH:
7
Temp.:
25 °C
Duration:
160.2 h
pH:
4
Temp.:
70 °C
Duration:
41.1 h
pH:
4
Temp.:
80 °C
Number of replicates:
2 replicates
Positive controls:
not specified
Negative controls:
not specified
Statistical methods:
no data
Preliminary study:
This test was performed with the test solutions at pH 4, 7 and 9 at 50 °C for 2.4 hours and 5 days respectively.
The results of this test permit an estimate as to whether the half-life period (t1/2) less than 2.4 h (case I) or lower than 10 % of hydrolysis after 5 days (case II). The corresponding estimates for conditions more representative of the environment (25 °C) are: case I: t1/2 < 1 day; case II: t1/2 > 1 year.
For all cases between those mentioned above, test 1 must be carried out for the individual pH- levels.
Result: The test substance is unstable at pH 9 at 50 °C; it has a half-life period shorter than one day at 25 °C and pH 9.
Test 1 must be carried out at pH 4 and pH 7.
Test performance:
The test substance is dissolved in aqueous buffer solution, the temperature and the pH are checked at pH 4, 7 and 9 respectively.
The decrease of the concentration with time is determined by HPLC, In case of hydrolysis, the logarithms of the concentration are plotted as a function of time, and if the result is a straight line, the reaction is considered to be of (pseudo-) first order. The rate constant and the half-life period are calculated using the slope of the line. When it is not practical to determine a rate constant directly at 25 °C, the half-life period can usually be estimated using the Arrhenius equation.
Transformation products:
not specified
pH:
4
Temp.:
25 °C
Hydrolysis rate constant:
0.002 s-1
DT50:
12 233.9 h
Type:
(pseudo-)first order (= half-life)
pH:
7
Temp.:
25 °C
Hydrolysis rate constant:
0.227 s-1
DT50:
84.8 h
Type:
(pseudo-)first order (= half-life)
pH:
9
Temp.:
25 °C
DT50:
< 1 d
Remarks on result:
other:
Remarks:
Results of preliminary test
Other kinetic parameters:
no data
Validity criteria fulfilled:
yes
Conclusions:
Half-life period of FAT 45176/A at pH 4 and pH 7 were 12233.9 h (about 1.4 years) and 84.8 h (about 3.5 days) at 25 °C respectively.
Executive summary:

Hydrolysis as a function of pH was performed with FAT 45176/A under GLP compliance according to OECD 111and EU C.7 guideline. Based on the study results, test substance at pH 4 has a half-life period of 12233.9 h (about 1.4 years) at 25 °C, at pH 7 has a half-life period of 84.8 h (about 3.5 days) at 25 °C, and is unstable at pH 9 with a half-life period of shorter than one day at 25 °C.

Description of key information

Half-life period of Reactive Orange 136 at pH 4 and pH 7 were 12233.9 h (about 1.4 years) and 84.8 h (about 3.5 days) at 25 °C respectively.

Key value for chemical safety assessment

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

Additional information

Hydrolysis as a function of pH was performed with FAT 45176/A under GLP compliance according to OECD 111and EU C.7 guideline. Based on the study results, test substance at pH 4 has a half-life period of 12233.9 h (about 1.4 years) at 25 °C, at pH 7 has a half-life period of 84.8 h (about 3.5 days) at 25 °C, and is unstable at pH 9 with a half-life period of shorter than one day at 25 °C.