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Hydrolysis

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Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
28 July 2014 to 04 February 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:
not specified
GLP compliance:
yes
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
- Sampling method: The test was sampled at intervals designed to give at least six spaced points between 10% and 90% hydrolysis.
- Sampling intervals/times for pH measurements: pH was measured at each sample taken for hydrolysis measurement.
- Sample storage conditions before analysis: ambient
Buffers:
- pH: 4
- Type and final molarity of buffer: The buffers were made in autoclaved DI maxima water and sterilised by filtering to 0.45μm
- Composition of buffer: 1640ml 0.1M acetic acid + 360ml 0.1M sodium acetate

- pH: 7
- Type and final molarity of buffer: The buffers were made in autoclaved DI maxima water and sterilised by filtering to 0.45μm
- Composition of buffer: 612ml 0.1M NaOH + 1200ml 0.1M monopotassium phosphate

- pH: 9
- Type and final molarity of buffer: The buffers were made in autoclaved DI maxima water and sterilised by filtering to 0.45μm
- Composition of buffer: 426ml 0.1M NaOH + 1200ml 0.1M boric acid
Details on test conditions:
TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: 0.0125g of test material made up to 250ml with filtered buffer solution. 100ml of this solution was added to each of two wheaton bottles labelled with the test pH, temperature and replicate number. The bottles were then sealed with aluminium crimp caps with butyl rubber septa.
Duration:
4 h
pH:
4
Temp.:
50 °C
Initial conc. measured:
14.05 g/L
Duration:
3.5 h
pH:
7
Temp.:
50 °C
Initial conc. measured:
20.57 g/L
Duration:
25.13 h
pH:
7
Temp.:
25 °C
Initial conc. measured:
20.94 g/L
Duration:
55.38 h
pH:
7
Temp.:
15 °C
Initial conc. measured:
20.34 g/L
Duration:
55.27 h
pH:
9
Temp.:
50 °C
Initial conc. measured:
20.57 g/L
Duration:
241.93 h
pH:
9
Temp.:
15 °C
Initial conc. measured:
20.94 g/L
Duration:
242.05 h
pH:
9
Temp.:
25 °C
Initial conc. measured:
20.94 g/L
Number of replicates:
2
Positive controls:
no
Negative controls:
no
Preliminary study:
A preliminary test was performed on the test substance at 50 ± 0.5°C at each of pH 4.0, 7.0 and 9.0 using appropriate buffer solutions. Two blank solutions were made by adding 100ml of buffer to each of two Wheaton bottles, the headspace was then purged with nitrogen and the bottles sealed with aluminium crimp caps with butyl rubber septa.
0.0250g of test material made up to 500ml with filtered buffer solution. 100ml of this solution was added to each of four Wheaton bottles labelled 4T1, 4T2, 4T3 and 4T4. The headspace was then purged with nitrogen and the bottles sealed with aluminium crimp caps with butyl rubber septa.
The test was sampled at 2.4 hours and 5 days. For each buffered system if less than 10% hydrolysis is observed after 5 days the chemical is considered to be hydrolytically stable (t½>1 year) and no further testing is required.
The results of the preliminary test showed that the test substance had hydrolysed more than 10% after 5 days hence there is a requirement for higher tier tests at all three pH conditions.
Transformation products:
not specified
Key result
pH:
4
Temp.:
15 °C
DT50:
0.5 h
Type:
(pseudo-)first order (= half-life)
Key result
pH:
4
Temp.:
25 °C
DT50:
0.5 h
Type:
(pseudo-)first order (= half-life)
Key result
pH:
4
Temp.:
50 °C
DT50:
0.17 h
Type:
(pseudo-)first order (= half-life)
Key result
pH:
7
Temp.:
15 °C
DT50:
8.2 h
Type:
(pseudo-)first order (= half-life)
Key result
pH:
7
Temp.:
25 °C
DT50:
3.75 h
Type:
(pseudo-)first order (= half-life)
Key result
pH:
7
Temp.:
50 °C
DT50:
> 0.25 - < 0.5 h
Type:
(pseudo-)first order (= half-life)
Key result
pH:
9
Temp.:
15 °C
DT50:
168.7 h
Type:
(pseudo-)first order (= half-life)
Key result
pH:
9
Temp.:
25 °C
DT50:
47.2 h
Type:
(pseudo-)first order (= half-life)
Key result
pH:
9
Temp.:
50 °C
DT50:
4.433 h
Type:
(pseudo-)first order (= half-life)
Validity criteria fulfilled:
not specified
Conclusions:
During the preliminary study Epofloc L-1R was observed to hydrolyse rapidly at pH4, 7 and 9. The hydrolysis was noticeably more rapid under lower pH conditions.
The premise of the test is that the hydrolysis reaction is pseudo first order hence rate of reaction is not proportional to concentration however when plotting the results from the definitive test it was noted that a plot of time against ln[a] gave a logarithmic curve indicating the hydrolysis is second order. To confirm this second order behaviour the results were replotted as time vs 1/[a], these graphs gave a more linear fit for the results.
Due to the second order nature of the hydrolysis reaction the rate constant is proportional to concentration therefore a generalised form for the rate of reaction is concentration dependant.

Description of key information

During the preliminary study Epofloc L-1R was observed to hydrolyse rapidly at pH 4, 7 and 9.

Key value for chemical safety assessment

Additional information

During the preliminary study Epofloc L-1R was observed to hydrolyse rapidly at pH4, 7 and 9. The hydrolysis was noticeably more rapid under lower pH conditions.

The premise of the test is that the hydrolysis reaction is pseudo first order hence rate of reaction is not proportional to concentration however when plotting the results from the definitive test it was noted that a plot of time against ln[a] gave a logarithmic curve indicating

the hydrolysis is second order. To confirm this second order behaviour the results were replotted as time vs 1/[a], these graphs gave a more linear fit for the results.

Due to the second order nature of the hydrolysis reaction the rate constant is proportional to concentration therefore a generalised form for the rate of reaction is concentration dependant.