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Hydrolysis

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Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Testing was conducted between 30 November 2011 and 02 June 2012.
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
GLP compliance:
yes
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
The buffer solutions were diluted to 5% using reverse osmosis water and filtered through a 0.2 µm membrane filter to ensure they were sterile before commencement of the test. Also these solutions were subjected to ultrasonication and dissolved oxygen was removed from the solution by sparging with nitrogen.

Preparation of samples
Sample solutions were prepared in stoppered glass flasks at a nominal concentration of 1 g/l in the three buffer solutions. A 1% co-solvent of acetonitrile was used to aid solubility.
The test solutions were split into individual vessels for each data point.
The solutions were shielded from light whilst maintained at the test temperature.

Preliminary test/Tier 1
Sample solutions at pH 4, 7 and 9 were maintained at 50.0 ± 0.5°C for a period of 120 hours.

Analysis of sample solutions
The sample solutions were taken from the water bath at various times and the pH of each solution recorded.
The concentration of the sample solution was determined by high performance liquid chromatography (HPLC).
Samples

Duplicate aliquots (A and B) of sample solution were diluted by a factor of 2 using acetonitrile.

Standards
Duplicate standard solutions of test item were prepared in acetonitrile:relevant buffer solution (1:1 v/v) at a nominal concentration of 500 mg/l.

Matrix blanks
Acetonitrile:relevant buffer solution (1:1 v/v)
Buffers:
Buffer solution
(pH) Components Concentration (mol/litre)
4 Potassium hydrogen phthalate 0.05
7 Disodium hydrogen orthophosphate (anhydrous) 0.03
Potassium dihydrogen orthophosphate 0.02
Sodium chloride 0.02
9 Disodium tetraborate 0.01
Sodium chloride 0.02

The buffer solutions were diluted to 5% using reverse osmosis water and filtered through a 0.2 µm membrane filter to ensure they were sterile before commencement of the test. Also these solutions were subjected to ultrasonication and dissolved oxygen was removed from the solution by sparging with nitrogen.



Estimation method (if used):
Not used.
Details on test conditions:
Refer to details on sampling and analytical methods.
Duration:
120 h
pH:
4
Initial conc. measured:
0.949 other: g/l - Sample A
Duration:
120 h
pH:
4
Initial conc. measured:
0.941 other: g/l - Sample B
Duration:
120 h
pH:
7
Initial conc. measured:
0.997 other: g/l - Sample A
Duration:
120 h
pH:
7
Initial conc. measured:
0.934 other: g/l - Sample B
Duration:
120 h
pH:
9
Initial conc. measured:
0.987 other: g/l - Sample A
Duration:
120 h
pH:
9
Initial conc. measured:
0.925 other: g/l Sample B
Number of replicates:
Duplicate aliquots (A and B) of sample solution were diluted by a factor of 2 using acetonitrile.
Positive controls:
no
Negative controls:
no
Statistical methods:
Not specified.
Preliminary study:
The mean peak areas relating to the standard and sample solutions are shown in table 6.2 (please see remarks on results including tables and figures section).

The test item concentrations at the given time points are shown in tables 6.3 - 6.5 incl. (please see remarks on results including tables and figures section).
Test performance:
Validation
The linearity of the detector response with respect to concentration was assessed over the nominal concentration ranges of 20.2 to 759 mg/l for the pH 4 buffer matrix, 23.1 to 868 mg/l for the pH 7 buffer matrix and 22.3 to 837 mg/l for the pH 9 buffer matrix. These were satisfactory with correlation coefficients of 1.000 being obtained for each matrix.
Transformation products:
not specified
Details on hydrolysis and appearance of transformation product(s):
Less than 10% hydrolysis after 5 days at 50°C, equivalent to a half-life greater than 1 year at 25°C.
Key result
pH:
4
Temp.:
25 °C
DT50:
> 1 yr
Key result
pH:
7
Temp.:
25 °C
DT50:
> 1 yr
Key result
pH:
9
Temp.:
25 °C
DT50:
> 1 yr
Other kinetic parameters:
None.
Details on results:
At pH4, 7 and 9 there was less than 10% hydrolysis after 5 days at 50°C, equivalent to a half-life greater than 1 year at 25°C.

Results

Preliminary test/Tier 1

The mean peak areas relating to the standard and sample solutions are shown in the following table:

Table 6.2

Solution

Mean Peak Area

Standard 531 mg/l

1.1839 x 107

Standard 503 mg/l

1.1241 x 107

Initial Sample A, pH 4

1.0595 x 107

Initial Sample B, pH 4

1.0506 x 107

Standard 531 mg/l

1.1961 x 107

Standard 503 mg/l

1.1302 x 107

Initial Sample A, pH 7

1.1218 x 107

Initial Sample B, pH 7

1.0510 x 107

Standard 531 mg/l

1.1966 x 107

Standard 503 mg/l

1.1305 x 107

Initial Sample A, pH 9

1.1110 x 107

Initial Sample B, pH 9

1.0417 x 107

Standard 529 mg/l

1.1836 x 107

Standard 549 mg/l

1.2353 x 107

24-Hour Sample A, pH 4

1.0367 x 107

24-Hour Sample B, pH 4

1.0812 x 107

Standard 529 mg/l

1.1933 x 107

Standard 549 mg/l

1.2406 x 107

24-Hour Sample A, pH 7

1.0863 x 107

24-Hour Sample B, pH 7

1.0800 x 107

Standard 529 mg/l

1.1983 x 107

Standard 549 mg/l

1.2364 x 107

24-Hour Sample A, pH 9

1.0368 x 107

24-Hour Sample B, pH 9

1.0327 x 107

Standard 533 mg/l

1.1384 x 107

Standard 639 mg/l

1.3831 x 107

120-Hour Sample A, pH 4

1.0314 x 107

120-Hour Sample B, pH 4

1.0311 x 107

Standard 533 mg/l

1.1253 x 107

Standard 639 mg/l

1.3774 x 107

120-Hour Sample A, pH 7

1.0656 x 107

120-Hour Sample B, pH 7

1.0783 x 107

Standard 533 mg/l

1.1356 x 107

Standard 639 mg/l

1.3771 x 107

120-Hour Sample A, pH 9

1.0052 x 107

120-Hour Sample B, pH 9

9.8957 x 106

 

The test item concentrations at the given time points are shown in the following tables:

Table 6.3      pH 4 at 50.0 ± 0.5ºC

Time (Hours)

Mean Concentration (g/l)

% of mean initial concentration (g/l)

A

B

A

B

0

0.949

0.941

-

-

24

0.924

0.963

97.8

102

120

0.959

0.959

102

102

Result:          Less than 10% hydrolysis after 5 days at 50°C, equivalent to a half-life greater than 1 year at 25°C.

Table 6.4      pH 7 at 50.0 ± 0.5ºC

Time (Hours)

Mean Concentration (g/l)

% of mean initial concentration (g/l)

A

B

A

B

0

0.997

0.934

-

-

24

0.962

0.956

99.6

99.1

120

0.999

1.01

103

105

Result:          Less than 10% hydrolysis after 5 days at 50°C, equivalent to a half-life greater than 1 year at 25°C.

Table 6.5      pH 9 at 50.0 ± 0.5ºC

Time (Hours)

Mean Concentration (g/l)

% of mean initial concentration (g/l)

A

B

A

B

0

0.987

0.925

-

-

24

0.918

0.914

96.0

95.6

120

0.938

0.924

98.1

96.6

Result:          Less than 10% hydrolysis after 5 days at 50°C, equivalent to a half-life greater than 1 year at 25°C. 

Validity criteria fulfilled:
yes
Conclusions:
The estimated half-life at 25°C of the test item at pH 4, 7 and 9 is greater than 1 year.
Executive summary:

Method

The determination was carried out using a procedure designed to be compatible with Method 111 of the OECD Guidelines for Testing of Chemicals, 13 April 2004.

Conclusion

The estimated half-lives at 25°C of the test item are shown in the following table:

Table 6.6

pH

Estimated half-life at 25°C

4

>1 year

7

>1 year

9

>1 year

Description of key information

The results of an OECD 111 test showed that the estimated half-life at 25°C of 1,1,3,3-tetramethylbutyl hydroperoxide at pH 4, 7 and 9 is greater than 1 year.

Key value for chemical safety assessment

Half-life for hydrolysis:
1 yr
at the temperature of:
50 °C

Additional information

One study is available conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines (OECD 111) 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. The estimated half-life at 25°C of 1,1,3,3-tetramethylbutyl hydroperoxide at pH 4, 7 and 9 is greater than 1 year.