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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:
09/03/-07/06/17
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)
GLP compliance:
yes (incl. certificate)
Radiolabelling:
no
Analytical monitoring:
yes
Buffers:
- pH: 4
- Type and final molarity of buffer:
- Composition of buffer: citric acid, sodium chloride, sodium hydroxide

- pH: 7
- Type and final molarity of buffer:
- Composition of buffer: phosphate mixture

- pH: 9
- Type and final molarity of buffer:
- Composition of buffer: boric acid, potassium chloride, sodum hydroxide
Number of replicates:
two replicates per temperature, three temperatures per pH
Positive controls:
no
Negative controls:
no
Preliminary study:
observed half-lifes: [pH 4] 4.1 h, [pH 7] 3.2 h, [pH 9] 0.6 h
Transformation products:
yes
No.:
#1
No.:
#2
No.:
#3
Details on hydrolysis and appearance of transformation product(s):
It was found that additional peaks at pH 9 come up from test item + H2O (#1) and from test item + 2 H2O (#2), respectively. Under acidic conditions, the reaction product test item - N2 (#3) has been identified via LC-MS measurement. Therefore, a radical reaction mechanism is supposed. At pH 7, the reaction products test item + H2O and test item - N2 were both identified.
Key result
pH:
4
Temp.:
20 °C
Hydrolysis rate constant:
0.001 h-1
DT50:
516.7 h
Type:
(pseudo-)first order (= half-life)
Key result
pH:
4
Temp.:
25 °C
Hydrolysis rate constant:
0.003 h-1
DT50:
214.9 h
Type:
(pseudo-)first order (= half-life)
Key result
pH:
7
Temp.:
20 °C
Hydrolysis rate constant:
0.002 h-1
DT50:
413.8 h
Type:
(pseudo-)first order (= half-life)
Key result
pH:
7
Temp.:
25 °C
Hydrolysis rate constant:
0.004 h-1
DT50:
171 h
Type:
(pseudo-)first order (= half-life)
Key result
pH:
9
Temp.:
20 °C
Hydrolysis rate constant:
0.028 h-1
DT50:
24.5 h
Type:
(pseudo-)first order (= half-life)
Key result
pH:
9
Temp.:
25 °C
Hydrolysis rate constant:
0.056 h-1
DT50:
12.4 h
Type:
(pseudo-)first order (= half-life)
Validity criteria fulfilled:
yes
Conclusions:
Depending on the pH of the environment a radical reaction mechanism (pH 4 and 7) or a hydrolytical mechanism (pH 9) can be observed.
Executive summary:

The degradation/hydrolysis reaction measured by pH 4, pH 7, and pH 9 can be assumed to be first or pseudo-first order. Due to this the half-lives for 20 °C and 25 °C can be calculated.

It is pointed out that the degradation reaction at pH 4 and partially at pH 7 does not come from hydrolysis, but is supposed to be a radical reaction mechanism.

Description of key information

For the chemical safety assessment, the half-life at pH 7 and 20 °C is selected as key value.

Key value for chemical safety assessment

Half-life for hydrolysis:
413.8 h
at the temperature of:
20 °C

Additional information