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Hydrolysis

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Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2015
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:
SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: MC-20/2014 (China)
- Expiration date of the lot/batch: 28 October 2019

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Frozen in the dark
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
The sample solutions were taken from the waterbath at various times and the pH of each solution were recorded.
Buffers:
The test system uses sterile buffer solutions at pH’s 4.0, 7.0 and 9.0.
Details on test conditions:
Performance of the Test:
Preparation of the Test Solutions:
Sample solutions were prepared in stoppered glass flasks at a nominal concentration of 1 g/L in the three buffer solutions. The concentration of each solution did not exceed the lesser of 0.01 mol/L or half the water solubility.

The test solutions were split into individual vessels for each data point. The solutions were shielded from light whilst maintained at the test temperature.

Preliminary Test:
Sample solutions were prepared at a nominal concentration of 1 g/L at pH 4, 7 and 9 and maintained at 50.0 ± 0.5 °C for a period of 120 hours.

Tier 2:
Results from the Preliminary test showed it was necessary to undertake further testing at pH 9, with solutions being maintained at 50.0 ± 0.5 °C, 60.0 ± 0.5 °C and 70.0 ± 0.5 °C for a period of 576, 288 and 144 hours respectively.
Duration:
48 h
pH:
9
Temp.:
50 °C
Initial conc. measured:
0.766 - 0.796 g/L
Duration:
72 h
pH:
9
Temp.:
50 °C
Initial conc. measured:
0.739 - 0.749 g/L
Duration:
168 h
pH:
9
Temp.:
50 °C
Initial conc. measured:
0.488 - 0.504 g/L
Duration:
240 h
pH:
9
Temp.:
50 °C
Initial conc. measured:
0.419 - 0.445 g/L
Duration:
336 h
pH:
9
Temp.:
50 °C
Initial conc. measured:
0.304 - 0.31 g/L
Duration:
432 h
pH:
9
Temp.:
50 °C
Initial conc. measured:
0.426 - 0.486 g/L
Duration:
576 h
pH:
9
Temp.:
50 °C
Initial conc. measured:
0.378 - 0.404 g/L
Duration:
4 h
pH:
9
Temp.:
60 °C
Initial conc. measured:
0.912 - 0.954 g/L
Duration:
24 h
pH:
9
Temp.:
60 °C
Initial conc. measured:
0.719 - 0.776 g/L
Duration:
72 h
pH:
9
Temp.:
60 °C
Initial conc. measured:
0.446 - 0.45 g/L
Number of replicates:
2
Positive controls:
no
Negative controls:
no
Preliminary study:
Preliminary pH 4 Test at 50.0 ± 0.5 ºC
Less than 10 % hydrolysis after 5 days at 50.0 ± 0.5 °C, equivalent to a half-life greater than 1 year at 25 °C.

Preliminary pH 7 Test at 50.0 ± 0.5 ºC
Less than 10% hydrolysis after 5 days at 50.0 ± 0.5 °C, equivalent to a half-life greater than 1 year at 25 °C.

Preliminary pH 9 Test at 50.0 ± 0.5 ºC
The extent of hydrolysis after 120 hours indicated that further tests (Tier 2), conducted at 50.0 ± 0.5°C, 60.0 ± 0.5°C and 70.0 ± 0.5 °C, were required to estimate the rate constant and half-life.
Test performance:
The kinetics of the study have been determined to be consistent with that of a pseudo-first order reaction as the graphs of log10 concentration versus time are straight lines.
Transformation products:
not measured
pH:
4
Temp.:
25 °C
DT50:
> 1 yr
pH:
7
Temp.:
25 °C
DT50:
> 1 yr
pH:
9
Temp.:
25 °C
Hydrolysis rate constant:
0 h-1
DT50:
222 d
Details on results:
pH 9 Test at 50.0 ± 0.5 ºC - Tier 2
Slope = -7.06E-04
kobs = 1.63E-03 hour-1
= 4.51E-07 second-1
t½ = 427 hours
= 17.8 days

pH 9 Test at 60.0 ± 0.5 ºC - Tier 2
Slope = -2.19E-03
kobs = 5.03E-03 hour-1
= 1.40E-06 second-1
t½ = 138 hours
= 5.74 days

pH 9 Test at 70.0 ± 0.5 ºC - Tier 2
Slope = -4.26E-03
kobs = 9.81E-03 hour-1
= 2.73E-06 second-1
t½ = 70.6 hours
= 2.94 days

pH 9 Arrhenius Data
From the graph of the data, the rate constant and half-life at 25 °C have been estimated to be as follows:
kobs = 1.30E-04 hour-1
3.61E-08 second-1
t½ = 5.34E+03 hours
= 222 days
Validity criteria fulfilled:
yes
Conclusions:
The half-life owing to hydrolysis at pH 4 and 7 was estimated to be >1 year, while at pH 9, it was estimated to be 222 days.
Executive summary:

Assessment of hydrolytic stability was carried out using a procedure designed to be compatible with Method C7 Abiotic Degradation, Hydrolysis as a Function of pH of Commission Regulation (EC) No 440/2008 of 30 May 2008 and Method 111 of the OECD Guidelines for Testing of Chemicals, 13 April 2004.

During the preliminary testing at pH 4 and pH 7, less than 10 % hydrolysis was seen after 5 days at 50.0 ± 0.5 °C, equivalent to a half-life greater than 1 year at 25 °C. At pH 9, the extent of hydrolysis (33.6 % with sample A and 36.3 % with sample B) after 120 hours indicated that further tests (Tier 2), conducted at 50.0 ± 0.5 °C, 60.0 ± 0.5 °C and 70.0 ± 0.5 °C, were required to estimate the rate constant and half-life. Based on the results obtained for tier 2 testing, the half-life for the test item was estimated to be 222 days at pH 9 and at 25 °C.

The kinetics of the study have been determined to be consistent with that of a pseudo-first order reaction as the graphs of log10 concentration versus time are straight lines. No significant peaks were observed at the approximate retention time of the test item on analysis of any matrix blank solutions. It has been observed that the rate of hydrolysis increases with an increase in pH.

Description of key information

Assessment of hydrolytic stability was carried out using a procedure designed to be compatible with Method C7 Abiotic Degradation, Hydrolysis as a Function of pH of Commission Regulation (EC) No 440/2008 of 30 May 2008 and Method 111 of the OECD Guidelines for Testing of Chemicals, 13 April 2004. During the preliminary testing at pH 4 and pH 7, less than 10 % hydrolysis was seen after 5 days at 50.0 ± 0.5 °C, equivalent to a half-life greater than 1 year at 25 °C. At pH 9, the extent of hydrolysis (33.6 % with sample A and 36.3 % with sample B) after 120 hours indicated that further tests (Tier 2), conducted at 50.0 ± 0.5 °C, 60.0 ± 0.5 °C and 70.0 ± 0.5 °C, were required to estimate the rate constant and half-life. Based on the results obtained for tier 2 testing, the half-life for the test item was estimated to be 222 days at pH 9 and at 25 °C.

Key value for chemical safety assessment

Half-life for hydrolysis:
1 yr
at the temperature of:
25 °C

Additional information