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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:
21-Apr-2010 to 23-Sep-2010
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Study conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results. The study report was conclusive, done to a valid guideline and the study was conducted under GLP conditions.
Qualifier:
according to
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Remarks:
Date of Certificate: November 12, 2008
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
Before and after incubation at 50 °C, 100 µL aliquots of the test solutions at each pH value were taken through a septum in order to avoid the contact with air and diluted in 10.5 mL of dimethyl sulfoxide in a headspace vial. The samples were analyzed by measuring the MS signal of di-tert-butyl peroxide (CAS# 110-05-4) after GC separation of the injected sample solution.

Buffers:
- Buffer Solution pH 4.0
- Buffer Solution pH 7.0
- Buffer Solution pH 9.0

The buffer solutions were autoclaved prior to first use.

Preparation of Buffer Solution pH 7.0 for Sample Preparation
387.6 mL of buffer pH 7.0 were diluted up to 1 L with water and adjusted to pH 7.0 with phosphoric acid.
Estimation method (if used):
Not used.
Duration:
120 h
pH:
4
Initial conc. measured:
34.77 mg/L
Duration:
120 h
pH:
7
Initial conc. measured:
34.25 mg/L
Duration:
120 h
pH:
9
Initial conc. measured:
77.92 mg/L
Number of replicates:
At least duplicate sample solutions were incubated.
Positive controls:
not specified
Negative controls:
not specified
Statistical methods:
Not specified.
Transformation products:
not specified
% Recovery:
100.2
pH:
4
Temp.:
50 °C
Duration:
120 h
% Recovery:
110
pH:
7
Temp.:
50 °C
Duration:
120 h
% Recovery:
92.6
pH:
9
Temp.:
50 °C
Duration:
120 h
pH:
4
Temp.:
50 °C
DT50:
> 1 yr
Type:
other: after 5 days at 50 °C, <10% were degraded, therefore the half-life time is >1 year
pH:
7
Temp.:
50 °C
DT50:
> 1 yr
Type:
other: after 5 days at 50 °C, <10% were degraded, therefore the half-life time is >1 year
pH:
9
Temp.:
50 °C
DT50:
> 1 yr
Type:
other: after 5 days at 50 °C, <10% were degraded, therefore the half-life time is >1 year
Other kinetic parameters:
None.

The results of the individual measurements are summarized in the attached table. The tabulated values represent rounded results obtained by calculation used the exact raw data.

 

A typical chromatogram of a standard solution is given in the attached Figure 1. Typical chromatograms of the test solutions after an incubation time of 5 days are given in the attached Figure 2 to Figure 4. The calibration curve of di-tert-butyl peroxide (CAS# 110-05-4) is shown in attached Figure 5. The calibration data are given in Table 2. The r2fit was 0.9993 (optimum 1.0000). This reflects the suitability of the GC-MS system within the range of 0.034 µg/mL to 1.100 µg/mL of test item.

 

The results of the tests at pH 4.0, pH 7.0 and pH 9.0 showed no significant degradation of di-tert-butyl peroxide (CAS# 110-05-4) at 50 °C.

Table 1       Results of the Preliminary Test of di-tert-butyl peroxide (CAS# 110-05-4)

 

Initial concen-tration measured

Mean Concen-tration

Concen-tration measured after 2.4 h incubation

Mean Concen-tration

Recovery

Concen-tration measured after 5 days incubation

Mean Concen-tration

Recovery

 

[µg/mL]

[µg/mL]

[µg/mL]

[µg/mL]

[%]

[µg/mL]

[µg/mL]

[%]

pH 4.0

 

34.77

 

36.78

105.7

38.77

34.84

100.2

 

 

42.44

27.88

 

25.52

34.85

36.80

24.81

38.47

36.71

49.54

37.9

 

48.18

 

 

26.15

 

 

23.31

pH 7.0

 

34.25

 

32.13

93.81

41.56

37.66

110.0

33.54

 

28.70

34.94

32.90

37.80

34.28

31.36

44.25

 

 

34.21

 

 

39.42

pH 9.0

 

77.92

 

81.64

104.8

99.50

72.15

92.6

 

 

92.88

76.20

81.63

92.03

79.64

81.66

27.63

 

 

71.56

 

 

49.31

 

 

Validity criteria fulfilled:
yes
Conclusions:
The degradation of di-tert-butyl peroxide (CAS# 110-05-4) was less than 10% after 5 days at 50 °C and pH 4, 7 and 9. di-tert-butyl peroxide (CAS# 110-05-4) was considered to be hydrolytically stable, and no further testing was necessary.
Executive summary:

The purpose of this study was to determine the hydrolysis behavior of di-tert-butyl peroxide (CAS# 110-05-4) in aqueous buffered solutions adjusted to pH 4.0, pH 7.0 and pH 9.0.

Hydrolysis is one of the most common reactions controlling abiotic degradation in the environment. This reaction is particularly relevant for substances with low biodegradability.

The hydrolysis determination of di-tert-butyl peroxide (CAS# 110-05-4) at different pH values was based on the OECD Guideline No. 111, “Hydrolysis as a Function of pH"; adoptedApril 13, 2004and the Council Regulation (EC) 440/2008 C.7.

The hydrolysis determination of di-tert-butyl peroxide (CAS# 110-05-4) at different pH values was based on the OECD Guideline No. 111, “Hydrolysis as a Function of pH”; adoptedApril 13, 2004.

 

The results of the tests at pH 4.0, pH 7.0 and pH 9.0 showed no significant degradation of di-tert-butyl peroxide (CAS# 110-05-4) at 50 °C. The degradation of di-tert-butyl peroxide (CAS# 110-05-4) was less than 10% after 5 days. These results are summarized in the table below.

 

pH

Hydrolysis after 5 days, 50 °C
[%]

4.0

< 10

7.0

< 10

9.0

< 10

 

According to the OECD Guideline No. 111 it can be concluded, that the estimated half-life time is higher than one year under representative environmental conditions (25 °C). Therefore, di-tert-butyl peroxide (CAS# 110-05-4) is considered to be hydrolytically stable, and no further testing was necessary.

 

Description of key information

Half-life of the substance at 25°C was predictd as greater than 1 year at pH = 4, pH = 7 and pH = 9.

Key value for chemical safety assessment

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

Additional information

Hydrolysis of the substance was assessed following a reliable GLP study according to the OECD 111 guidelines (Elsner, 2010). In buffer solutions at pH = 4.0, pH = 7.0 and pH = 9.0 covering the extremes and typical environmental pHs, the substance at an initial concentration of 0.1 mg/L was monitored at 2.4h and 120h by GC-MS at 50°C in a preliminary test. Less than 10% of the substance was degraded after 120h. Following the guidelines, the study was terminated since no abiotic degradation was observed at this stage of the test. It was finally concluded that the half-life of the substance at 25°C was over 1 year at pH = 4, pH = 7 and pH = 9.