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Hydrolysis

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Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Reliable study not performed under GLP
Qualifier:
according to
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Deviations:
yes
Remarks:
see "Principles of method if other than guideline"
Principles of method if other than guideline:
Study procedures were based on OECD guideline 111 (6) with 2 adaptations. Only the screening part (Tier 1) of the hydrolysis study was conducted.

Adaptations from OECD guideline 111:
• The screening test was performed at a test temperature of 12°C instead of the required 50°C according to the guideline because 12°C is a value that is often used in environmental simulation software.

• No Thymol was added to the buffer solutions as, based on microbiological experience, the addition of Thymol as a disinfectant is not necessary because the buffer solutions were also sterilized.
GLP compliance:
no
Remarks:
endpoint could be waived (readily biodegradable), non-GLP screening study conducted to gain general hydrolysis information
Radiolabelling:
no
Analytical monitoring:
yes
Buffers:
- pH:
- Type and final molarity of buffer:
- Composition of buffer:
Sterile test buffer solutions of pH 4, 7 and 9 were prepared according to the description in Annex 3 of OECD 111 and purged with nitrogen for at least 5 minutes. Sterilization of the buffer solutions was performed by autoclaving at 121°C for at least 20 minutes.
Details on test conditions:
TEST SYSTEM
- Type, material and volume of test flasks, other equipment used:
All glassware and buffer solutions were sterilised. Buffer solutions were flushed with nitrogen to minimise oxidation. Test vessels (10 mL glass HPLC vials with crip caps) were kept under dark conditions to avoid eventual photo degradation. A temperature controlled water bath was used; temperature was measured using a calibrated thermometer. pH was measured using a pH meter.
- Sterilisation method:
Sterilization of glassware was performed by heating at 180°C for at least 30 minutes.
- Lighting: dark
- Measures taken to avoid photolytic effects: samples were kept in water bath in the dark
- Measures to exclude oxygen: samples were ppurged with nitrgen for at least 5 min.

TEST MEDIUM
- Volume used/treatment: 10 mL
- Kind and purity of water: HPLC water
- Preparation of test medium:
Sterile glass test vials were filled with 9.925 mL of buffer solutions pH 4 and 9 and 9.7 mL of the buffer solution pH 7. The vials were closed tightly and placed in the dark in a thermostatically controlled water bath at a temperature of 12°C.
A stock solution with a test substance concentration of about 500 mg/L in acetonitrile was prepared. Diluted stock solutions with a concentration of 20 mg/L (pH 4, 9) and 5 mg/L (pH 7) in acetonitrile were prepared. An amount of 75 µL (pH 4, 9) and 300 µL (pH 7) of the diluted stock solution was added to the buffer solutions to reach a test substance concentration in the buffer solutions of about 150 µg/L
- Renewal of test solution: no
- Identity and concentration of co-solvent: 0.75 - 3% Acetonitrile
Preliminary study:
pH value of 4
The temperature during the test varied between 11.9 and 12.1°C. It was observed that about 75% of the test substance was hydrolyzed after 1 day. Using the information gathered during the screening hydrolysis test also a calculation of the half-life (t ½) was determined by applying the Arrhenius relationship, the relation between the logarithmic value of the concentration of the test substance and the time. The half-life for the test substance was calculated to be 11 hours.

pH value of 7
The temperature during the test varied between 11.8 and 12.0°C. It was observed that about 71% of the test substance was hydrolyzed after 1 day. Using the information gathered during the screening hydrolysis test also a calculation of the half-life (t ½) was determined by applying the Arrhenius relationship, the relation between the logarithmic value of the concentration of the test substance and the time. The half-life for the test substance was calculated to be 11 hours.

pH value of 9
The temperature during the test varied between 11.8 and 12.0°C. It was observed that about 76% of the test substance was hydrolyzed in 1 day. Using the information gathered during the screening hydrolysis test also a calculation of the half-life (t ½) was determined by applying the Arrhenius relationship, the relation between the logarithmic value of the concentration of the test substance and the time. The half-life for the test substance was calculated to be 13 hours.
Transformation products:
not measured
pH:
4
Temp.:
12 °C
Hydrolysis rate constant:
0.001 min-1
DT50:
11 h
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: equation: y=-0.0005x-1.097, r2=0.9782
pH:
7
Temp.:
12 °C
Hydrolysis rate constant:
0.001 min-1
DT50:
11 h
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: Equation: y=-0.0005x-0.877, r2=0.9939
pH:
9
Temp.:
12 °C
Hydrolysis rate constant:
0.001 min-1
DT50:
13 h
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: Equation: y=-0.0004x-0.885, r2=0.9869
Details on results:
TEST CONDITIONS
- pH, sterility, temperature, and other experimental conditions maintained throughout the study: Yes

Table II: Results screening hydrolysis, pH 4

Sample

Time
 from start test

Conc.
(Ct)

Hydrolysis

Log Ct

 

min.

mg/L

%

 

t=0 min.

0

0.093

0.0

-1.03

t=30 min.

30

0.079

14.1

-1.10

t= 60 min.

60

0.077

15.7

-1.11

t= 90 min.

90

0.070

23.0

-1.15

t= 120 min.

120

0.066

27.2

-1.18

t=180 min.

180

0.062

30.8

-1.21

t= 270 min.

270

0.055

37.7

-1.26

t= 1440 min.

1440

0.018

75.1

-1.76

Table III: Results screening hydrolysis, pH 9

Sample

Time
 from start test

Conc.
(Ct)

Hydrolysis

Log Ct

 

min.

mg/L

%

 

t=0 min.

0

0.141

0.0

-0.85

t= 30 min.

30

0.129

7.5

-0.89

t= 60 min.

60

0.124

10.9

-0.91

t= 90 min.

90

0.124

11.3

-0.91

t= 120 min.

120

0.112

18.4

-0.95

t= 180 min.

180

0.109

20.2

-0.96

t= 240 min.

240

0.095

29.2

-1.02

t= 1440 min.

1440

0.028

71.4

-1.55

Table IV: Results screening hydrolysis, pH 9

Sample

Time
 from start test

Conc.
(Ct)

Hydrolysis

Log Ct

 

min.

mg/L

%

 

t=0 min.

0

0.141

0.0

-0.85

t= 30 min.

30

0.135

4.0

-0.87

t= 60 min.

60

0.125

11.3

-0.90

t= 90 min.

90

0.113

19.9

-0.95

t= 120 min.

120

0.111

20.9

-0.95

t= 180 min.

180

0.107

23.9

-0.97

t= 1560 min.

1560

0.034

75.8

-1.47

Validity criteria fulfilled:
yes
Conclusions:
The screening hydrolysis test was performed separately for each pH value tested. The test substance showed hydrolysis at pH values 4, 7 and 9. The half-life for pH 4 and 7 was calculated to be 11 hours, whereas for pH 9 the half-life was calculated to be slightly higher, 13 hours. The half-life for all pH values tested was calculated to be around 12 hours.
Executive summary:

A screening hydrolysis ofO-(2-ethylhexyl) O,O-tert-pentyl peroxycarbonatewas determined at 12°C and at the pH values of 4, 7 and 9 in agreement with OECD guideline 111.Hydrolysis of O-(2-ethylhexyl) O,O-tert-pentyl peroxycarbonatewas observed at pH values 4, 7 and 9.

 

At a pH value of 4 the half-life (t½) forO-(2-ethylhexyl) O,O-tert-pentyl peroxycarbonateat a temperature of 12°C was calculated to be 11 hours.

 

At a pH value of 7 the half-life (t½) forO-(2-ethylhexyl) O,O-tert-pentyl peroxycarbonateat a temperature of 12°C was calculated to be 11 hours.

 

At a pH value of 9 the half-life (t½) forO-(2-ethylhexyl) O,O-tert-pentyl peroxycarbonateat a temperature of 12°C was calculated to be 13 hours.

Description of key information

A screening hydrolysis of O-(2-ethylhexyl) O,O-tert-pentyl peroxycarbonate was determined at 12°C and at the pH values of 4, 7 and 9 in agreement with OECD guideline 111. Hydrolysis of O-(2-ethylhexyl) O,O-tert-pentyl peroxycarbonate was observed at pH values 4, 7 and 9.

 

At a pH value of 4 the half-life (t½) forO-(2-ethylhexyl) O,O-tert-pentyl peroxycarbonateat a temperature of 12°C was calculated to be 11 hours.

 

At a pH value of 7 the half-life (t½) forO-(2-ethylhexyl) O,O-tert-pentyl peroxycarbonateat a temperature of 12°C was calculated to be 11 hours.

 

At a pH value of 9 the half-life (t½) forO-(2-ethylhexyl) O,O-tert-pentyl peroxycarbonateat a temperature of 12°C was calculated to be 13 hours.

In a separate study hydrolysis products were identfied.

Tert-Amylperoxy-2-ethylhexylcarbonate degrades to 2-ethylhexanol (CAS 104 -76 -7), tert amyl alcohol (CAS 75 -85 -4), Acetone (CAS 67-64-1) and Ethanol (CAS 64-17-5).

Key value for chemical safety assessment

Half-life for hydrolysis:
11 h
at the temperature of:
12 °C

Additional information