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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:
2011-11-22 to 2012-09-04
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)
Version / remarks:
13 April 20
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)
Version / remarks:
31 May 2008
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Radiolabelling:
no
Analytical monitoring:
yes
Buffers:
- pH: 4, 7, and 9
- Composition of buffer: Buffer solution pH = 4: 4 mL 0.2 M sodium hydroxide and 500 mL 0.2 M potassium hydrogen phthalate were diluted to 2000 mL with ultra-pure water. Buffer solution pH = 7: 295.6 mL 0.2 M sodium hydroxide and 500 mL 0.2 M potassium dihydrogen phosphate were diluted to 2000 mL with ultra-pure water. Buffer solution pH = 9: 214 mL 0.2 M sodium hydroxide and 500 mL 0.2 M boric acid and potassium chloride were diluted to 2000 mL with ultra-pure water.
Details on test conditions:
TEST SYSTEM AND CONDITIONS:
The hydrolysis was examined at three different pH values (pH = 4, 7 and 9) in the dark.
Temperature: 50 °C +/-0.5 °C, 37 °C +/- 0.5 °C and 15 °C +/- 0.5 °C.
Light and oxygen: The hydrolysis reaction was carried out using a dark thermostat to avoid photolytic effects. Nitrogen was bubbled into the water before the preparation of the solutions in order to exclude oxygen. All glassware, water and buffer solution were sterilised.
The sterile buffer solutions were prepared using reagent grade chemicals and sterile ultra-pure water.
The pH of each buffer solution was checked with a calibrated pH meter.
The samples were analysed directly after preparation.
Sterility confirmation tests were performed at each pH level at the end of the hydrolysis experiments.

Sample preparation for identification of transformation products (tier 3 study):
- HPLC-MS analysis: Solution 1 mg test item/mL in acetonitrile : water at a ratio 1:1 (Storage: 4 hours at 40 °C)
- GC-FID analysis: Solution 100 μg test item/mL in water (Storage: 8 hours at 50°C)
Duration:
1 200 min
pH:
4
Temp.:
15 °C
Initial conc. measured:
10.9 mg/L
Duration:
960 min
pH:
4
Temp.:
37 °C
Initial conc. measured:
10.9 mg/L
Duration:
140 min
pH:
4
Temp.:
50 °C
Initial conc. measured:
9.06 mg/L
Duration:
4 380 min
pH:
7
Temp.:
15 °C
Initial conc. measured:
9.09 mg/L
Duration:
580 min
pH:
7
Temp.:
37 °C
Initial conc. measured:
9.09 mg/L
Duration:
170 min
pH:
7
Temp.:
50 °C
Initial conc. measured:
9.09 mg/L
Duration:
5 760 min
pH:
9
Temp.:
15 °C
Initial conc. measured:
10.7 mg/L
Duration:
1 300 min
pH:
9
Temp.:
37 °C
Initial conc. measured:
10.7 mg/L
Duration:
720 min
pH:
9
Temp.:
50 °C
Initial conc. measured:
10.7 mg/L
Number of replicates:
Two-three samples were analysed at the start of the study at each pH value. Two separate tubes were analysed at each analytical occasion of hydrolysis test.
One sample was taken from the control vessel.
Negative controls:
yes
Remarks:
control buffer samples
Statistical methods:
The TBPND concentrations were calculated applying the calibration equations (linear regression curves).
For the calculation of the half lives of reactions at the different pH values the ln-transformed data of TBPND concentrations were plotted against time. Linear regression lines were fitted on the data. The rate constant and the half live of the reactions were obtained from the slope of this linear regression lines.
Calculation of the half lives of reactions at 20 and 25 °C: Applying Arrhenius equation the rate constant and half-live at pH = 4, 7 and 9 were calculated at 20 and 25°C. The ln-transformed data of rate constants at three temperatures of the hydrolysis test were plotted against 1/T (T= t+273.15 °C). A line was fitted on the data and the rate constants at 20 and 25 °C were calculated from the constants and slopes of linear regression lines
Preliminary study:
In the course of the preliminary test TBPND proved to be hydrolytically unstable at pH = 4, pH = 7 and pH = 9.
Transformation products:
yes
No.:
#1
No.:
#2
% Recovery:
41
pH:
4
Temp.:
15 °C
Duration:
1 200 min
% Recovery:
11
pH:
4
Temp.:
37 °C
Duration:
960 min
% Recovery:
19
pH:
4
Temp.:
50 °C
Duration:
140 min
% Recovery:
8
pH:
7
Temp.:
15 °C
Duration:
4 380 min
% Recovery:
13
pH:
7
Temp.:
37 °C
Duration:
580 min
% Recovery:
17
pH:
7
Temp.:
50 °C
Duration:
170 min
% Recovery:
49
pH:
9
Temp.:
15 °C
Duration:
5 760 min
% Recovery:
12
pH:
9
Temp.:
37 °C
Duration:
1 300 min
% Recovery:
0
pH:
9
Temp.:
50 °C
Duration:
720 min
Key result
pH:
4
Temp.:
15 °C
Hydrolysis rate constant:
0.001 min-1
DT50:
17 h
Type:
(pseudo-)first order (= half-life)
Key result
pH:
4
Temp.:
37 °C
Hydrolysis rate constant:
0.002 min-1
DT50:
5.1 h
Type:
(pseudo-)first order (= half-life)
Key result
pH:
4
Temp.:
50 °C
Hydrolysis rate constant:
0.013 min-1
DT50:
0.9 h
Type:
(pseudo-)first order (= half-life)
Key result
pH:
7
Temp.:
15 °C
Hydrolysis rate constant:
0.001 min-1
DT50:
21 h
Type:
(pseudo-)first order (= half-life)
Key result
pH:
7
Temp.:
37 °C
Hydrolysis rate constant:
0.003 min-1
DT50:
3.3 h
Type:
(pseudo-)first order (= half-life)
Key result
pH:
7
Temp.:
50 °C
Hydrolysis rate constant:
0.011 min-1
DT50:
1.1 h
Type:
(pseudo-)first order (= half-life)
Key result
pH:
9
Temp.:
15 °C
Hydrolysis rate constant:
0 min-1
DT50:
127 h
Type:
(pseudo-)first order (= half-life)
Key result
pH:
9
Temp.:
37 °C
Hydrolysis rate constant:
0.002 min-1
DT50:
7.3 h
Type:
(pseudo-)first order (= half-life)
Key result
pH:
9
Temp.:
50 °C
Hydrolysis rate constant:
0.009 min-1
DT50:
1.3 h
Type:
(pseudo-)first order (= half-life)
Other kinetic parameters:
Applying Arrhenius equation the rate constant and half-live at pH = 4, 7 and 9 were calculated at 20 °C and 25°C:
- Temperature: 20 °C, pH = 4: half-live 13 hours (771 minutes),
- Temperature: 20 °C, pH = 7: half-live 14 hours (817 minutes),
- Temperature: 20 °C, pH = 9: half-live 64 hours (3846 minutes),
- Temperature: 25 °C, pH = 4: half-live 8 hours (501 minutes),
- Temperature: 25 °C, pH = 7: half-live 9 hours (520 minutes),
- Temperature: 25 °C, pH = 9: half-live 32 hours (1924 minutes).
Details on results:
Applying Arrhenius equation the rate constant and half-live at pH = 4, 7 and 9 were calculated at 20 °C and 25°C. Results of the sterility confirmation test: There were no microorganisms detected by the sterility confirmation tests.

Tier 3 results (Identification of transformation products):

On the basis of MS spectra (HPLC-MS analysis) and retention times (GC-FID analysis) the hydrolysis degradation products of tert-butyl peroxyneodecanoate (7,7-dimethyloctanoic acid and tert-butanol) were identified successfully.

Validity criteria fulfilled:
yes
Conclusions:
The hydrolysis of tert-butyl peroxyneodecanoate (TBPND) in different aqueous buffer solutions (pH = 4, 7 and 9) at 15, 37 and 50 °C was investigated using HPLC-UV. Measurements revealed a fast hydrolysis of TBPND (half-live: 0.9 hours) at pH = 4 and 50 °C. The degradation products of the hydrolysis of tert-butyl peroxyneodecanoate (TBPND) (7,7-dimethyloctanoic acid and tert-butanol) were identified qualitatively using HPLC-MS and GC-FID, respectively.
Executive summary:

The hydrolysis of tert-butyl peroxyneodecanoate (TBPND) and the identifiaction of the decomposition products was assessed in accordance with the OECD guideline 111 and the EU method C.7. The hydrolysis of tert-butyl peroxyneodecanoate (TBPND) in different aqueous buffer solutions (pH = 4, 7 and 9) at 15, 37 and 50 °C was investigated using HPLC-UV. Measurements revealed a fast hydrolysis of TBPND (half-live: 0.9 hours) at pH = 4 and 50 °C. Applying Arrhenius equation the rate constant and half-live at pH = 4, 7 and 9 were calculated at 20 and 25°C. The half-life at pH = 4, 7 and 9 at 20 °C are 13 hours, 14 hours and 64 hours, respectively. The half-life at pH = 4, 7 and 9 at 25 °C are 8 hours, 9 hours and 32 hours, respectively. It could be shown that the hydrolysis of TBPND was dependent from the pH and the temperature of the aqueous media. The degradation products (7,7-dimethyloctanoic acid and tert-butanol) were successfully identified using HPLC-MS and GC-FID, respectively.

Description of key information

The hydrolysis of tert-butylperoxyneodecanoate(TBPND) in different aqueous buffer solutions (pH = 4, 7 and 9) at 15, 37 and 50 °C was investigated using HPLC-UV. Measurements revealed a fast hydrolysis of TBPND (half-live: 0.9 hours) at pH = 4 and 50 °C. The degradation products of the hydrolysis of tert-butylperoxyneodecanoate(TBPND) (7,7-dimethyloctanoic acid andtert-butanol) were identified qualitatively using HPLC-MS and GC-FID, respectively.

Key value for chemical safety assessment

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

Additional information

The hydrolysis of tert-butyl peroxyneodecanoate (TBPND) and the identifiaction of the decomposition products was assessed in accordance with the OECD guideline 111 and the EU method C.7. The hydrolysis of tert-butyl peroxyneodecanoate (TBPND) in different aqueous buffer solutions (pH = 4, 7 and 9) at 15, 37 and 50 °C was investigated using HPLC-UV. Measurements revealed a fast hydrolysis of TBPND (half-live: 0.9 hours) at pH = 4 and 50 °C. Applying Arrhenius equation the rate constant and half-live at pH = 4, 7 and 9 were calculated at 20 and 25°C. The half-life at pH = 4, 7 and 9 at 20 °C are 13 hours, 14 hours and 64 hours, respectively. The half-life at pH = 4, 7 and 9 at 25 °C are 8 hours, 9 hours and 32 hours, respectively. It could be shown that the hydrolysis of TBPND was dependent from the pH and the temperature of the aqueous media. The degradation products (7,7-dimethyloctanoic acid and tert-butanol) were successfully identified using HPLC-MS and GC-FID, respectively.