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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:
Testing was conducted between 15 June 2011 and 20 December 2011.
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
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:
equivalent or similar to
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Deviations:
no
Qualifier:
equivalent or similar to
Guideline:
EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
The buffer solutions were 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 degassing with nitrogen to minimise dissolved oxygen content.

Preparation of samples:
Sample solutions were prepared in stoppered glass flasks at a nominal concentration of 6 g/l in the three buffer solutions.
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 144 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 10 using reverse osmosis water.

Standards:
Standard solutions of test item were prepared in relevant buffer solution:reverse osmosis water (1:9 v/v) covering a nominal concentration range of 60 to 900 mg/l including a duplicate at a nominal concentration of approximately 600 mg/l.

Matrix blanks
Relevant buffer solution:reverse osmosis water (1:9 v/v).
Buffers:
Specification of buffer solutions:

Buffer solution (pH 4):
Components: Potassium hydrogen phthalate
Concentration (mol dm-3): 0.05

Buffer solution (pH 7):
Components: Disodium hydrogen orthophosphate (anhydrous), Potassium dihydrogen orthophosphate, Sodium chloride
Concentration (mol dm-3): 0.03, 0.02, 0.02

Buffer solution (pH 9):
Components: Dosodium tetraborate, Sodium chloride
Concentration (mol dm-3): 0.01, 0.02

The buffer solutions were 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 degassing with nitrogen to minimise dissolved oxygen content.


Estimation method (if used):
Not used.
Details on test conditions:
Refer to details on sampling and analytical methods.
Duration:
144 h
pH:
4
Initial conc. measured:
6 other: g/l: theoretical concentration
Duration:
144 h
pH:
7
Initial conc. measured:
6 other: g/l: theoretical concentration
Duration:
144 h
pH:
9
Initial conc. measured:
6 other: g/l: theoretical concentration
Number of replicates:
Duplicate aliquots (A and B) of sample solution were diluted by a factor of 10 using reverse osmosis water.
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 any other information on results including tables and figures section.
The calibration curves from which the sample concentrations were interpolated are shown in Figure 11.1 to Figure 11.12 (see attached background material - calibration curves).
Transformation products:
no
Details on hydrolysis and appearance of transformation product(s):
At pH4, 7 and 9 there was less than 10% hydrolysis over 120 hours 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 pH 4, 7 and 9 there was less than 10% hydrolysis over 120 hours at 50°C, equivalent to a half-life greater than 1 year at 25°C.

Preliminary test/Tier 1

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

Solution

Mean Peak Area

Standard 924 mg/l

2.289 x 108

Standard 822 mg/l

2.104 x 108

Standard 616 mg/l

1.457 x 108

Standard 620 mg/l

1.607 x 108

Standard 308 mg/l

7.038 x 107

Standard 103 mg/l

1.591 x 107

Standard 61.6 mg/l

5.680 x 106

Matrix Blank

0.000

Initial Sample A, pH 4

1.239 x 108

Initial Sample B, pH 4

1.117 x 108

Standard 909 mg/l

3.244 x 108

Standard 808 mg/l

2.595 x 108

Standard 606 mg/l

1.518 x 108

Standard 697 mg/l

2.431 x 108*

Standard 303 mg/l

2.982 x 108

Standard 101 mg/l

6.163 x 107

Standard 60.6 mg/l

1.398 x 106

continued

Solution

Mean Peak Area

Matrix Blank

0.000

Initial Sample A, pH 7

1.892 x 108

Initial Sample B, pH 7

1.999 x 108

Standard 931 mg/l

4.030 x 108

Standard 827 mg/l

3.268 x 108

Standard 620 mg/l

2.034 x 108

Standard 671 mg/l

2.352 x 108

Standard 310 mg/l

6.579 x 107

Standard 103 mg/l

1.118 x 107

Standard 62.0 mg/l

4.300 x 106

Matrix Blank

0.000

Initial Sample A, pH 9

1.775 x 108

Initial Sample B, pH 9

1.860 x 108

Standard 924 mg/l

2.978 x 108

Standard 822 mg/l

2.164 x 108

Standard 643 mg/l

1.734 x 108

Standard 604 mg/l

1.530 x 108

Standard 308 mg/l

4.684 x 107

Standard 103 mg/l

5.441 x 106

Standard 61.6 mg/l

2.222 x 106

Matrix Blank

0.000

24-Hour Sample A, pH 4

1.506 x 108

24-Hour Sample B, pH 4

1.606 x 108

Standard 909 mg/l

2.850 x 108

Standard 808 mg/l

2.287 x 108

Standard 606 mg/l

1.560 x 108

Standard 697 mg/l

1.809 x 108

Standard 303 mg/l

6.120 x 107

Standard 101 mg/l

1.135 x 107

Standard 60.6 mg/l

3.310 x 106

Matrix Blank

0.000

24-Hour Sample A, pH 7

1.190 x 108

24-Hour Sample B, pH 7

1.376 x 108

*This point was an outlier and therefore has not been used in the calculations. 


Solution

Mean Peak Area

Standard 931 mg/l

3.148 x 108

Standard 827 mg/l

2.059 x 108

Standard 609 mg/l

1.431 x 108

Standard 633 mg/l

1.613 x 108

Standard 310 mg/l

5.071 x 107

Standard 103 mg/l

1.013 x 107

Standard 62.0 mg/l

4.043 x 106

Matrix Blank

0.000

24-Hour Sample A, pH 9

1.569 x 108

24-Hour Sample B, pH 9

1.435 x 108

Standard 924 mg/l

3.156 x 108

Standard 822 mg/l

2.591 x 108

Standard 616 mg/l

1.774 x 108

Standard 640 mg/l

1.919 x 108

Standard 308 mg/l

5.006 x 107

Standard 103 mg/l

6.765 x 106

Standard 61.6 mg/l

1.561 x 106

Matrix Blank

0.000

120-Hour Sample A, pH 4

1.798 x 108

120-Hour Sample B, pH 4

1.852 x 108

Standard 909 mg/l

3.888 x 108

Standard 808 mg/l

3.242 x 108

Standard 606 mg/l

1.963 x 108

Standard 604 mg/l

2.014 x 108

Standard 308 mg/l

5.864 x 107

Standard 103 mg/l

1.123 x 107

Matrix Blank

0.000

120-Hour Sample A, pH 7

2.050 x 108

120-Hour Sample B, pH 7

1.929 x 108

continued

Solution

Mean Peak Area

Standard 931 mg/l

3.522 x 108

Standard 827 mg/l

2.846 x 108

Standard 609 mg/l

1.993 x 108

Standard 633 mg/l

2.025 x 108

Standard 310 mg/l

6.444 x 107

Standard 103 mg/l

1.201 x 107

Standard 62.0 mg/l

5.471 x 106

Matrix Blank

0.000

120-Hour Sample A, pH 9

1.829 x 108

120-Hour Sample B, pH 9

1.704 x 108

Standard 924 mg/l

3.427 x 108

Standard 822 mg/l

2.990 x 108

Standard 616 mg/l

1.956 x 108

Standard 640 mg/l

2.084 x 108

Standard 308 mg/l

5.992 x 107

Standard 103 mg/l

6.774 x 106

Standard 61.6 mg/l

2.303 x 106

Matrix Blank

0.000

144-Hour Sample A, pH 4

2.072 x 108

144-Hour Sample B, pH 4

2.069 x 108

Standard 909 mg/l

5.135 x 108

Standard 808 mg/l

4.329 x 108

Standard 606 mg/l

2.947 x 108

Standard 604 mg/l

2.681 x 108

Standard 308 mg/l

1.037 x 108

Standard 103 mg/l

2.988 x 107

Standard 60.6 mg/l

1.719 x 107

Matrix Blank

0.000

144-Hour Sample A, pH 7

2.365 x 108

144-Hour Sample B, pH 7

2.506 x 108

Solution

Mean Peak Area

Standard 931 mg/l

4.002 x 108

Standard 827 mg/l

3.175 x 108

Standard 620 mg/l

1.715 x 108

Standard 655 mg/l

1.728 x 108

Standard 310 mg/l

6.619 x 107

Standard 103 mg/l

1.664 x 107

Standard 62.0 mg/l

3.959 x 106

Matrix Blank

0.000

144-Hour Sample A, pH 9

1.500 x 108

144-Hour Sample B, pH 9

1.487 x 108

The calibration curves from which the sample concentrations were interpolated are shown in attached background material (see calibration curves).

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

pH 4 at 50.0 ± 0.5ºC

 

Time (Hours)

Initial (A)

Initial (B)

24 (A)

24 (B)

120 (A)

120 (B)

144 (A)

144 (B)

Concentration (g/l)

5.15

4.68

6.19

6.44

6.40

6.52

6.48

6.48

% of theoretical concentration (6.03 g/l)

85.4

77.5

103

107

106

108

107

107

Result: Less than 10% hydrolysis over 120 hours at 50°C, equivalent to a half-life greater than 1 year at 25°C*

pH 7 at 50.0 ± 0.5ºC

 

Time (Hours)

Initial (A)

Initial (B)

24 (A)

24 (B)

120 (A)

120 (B)

144 (A)

144 (B)

Concentration (g/l)

6.88

7.09

5.15

5.70

6.24

6.01

5.50

5.73

% of theoretical concentration (6.14 g/l)

112

116

83.8

92.9

102

97.9

89.6

93.3

Result: Less than 10% hydrolysis over 120 hours at 50°C, equivalent to a half-life greater than 1 year at 25°C*

pH 9 at 50.0 ± 0.5ºC

 

Time (Hours)

Initial (A)

Initial (B)

24 (A)

24 (B)

120 (A)

120 (B)

144 (A)

144 (B)

Concentration (g/l)

5.74

5.90

6.48

6.13

6.01

5.72

5.70

5.68

% of theoretical concentration (6.05 g/l)

94.9

97.6

107

101

99.3

94.6

94.2

93.8

 

Result: Less than 10% hydrolysis over 120 hours at 50°C, equivalent to a half-life greater than 1 year at 25°C

 *

Results from the analysis of the pH 4 and pH 7 initial time points were considered inconsistent with the subsequent data, therefore the percentage of theoretical concentration has been presented, see Overall remarks, Discussion.

Validity criteria fulfilled:
not applicable
Conclusions:
The estimated half-life at 25°C of the test material at pH 4, 7 and 9 is greater than 1 year.
Executive summary:

Thehydrolysis determination was carried out using a procedure designed to be compatible with Method C7 Abiotic Degradation, Hydrolysis as a Function of pH of Commission Regulation (EC) No 440/2008 of 30 May 2008 and Method 111 of the OECD Guidelines for Testing of Chemicals, 13 April 2004.

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

pH

Estimated half-life at 25°C

4

>1 year

7

>1 year

9

>1 year

Description of key information

The estimated half-lives at 25°C of the test item, 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:
25 °C

Additional information

The determination was carried out using a procedure designed to be compatible with Method C7 Abiotic Degradation, Hydrolysis as a Function of pH of Commission Regulation (EC) No 440/2008 of 30 May 2008 and Method 111 of the GECD Guidelines for Testing of Chemicals, 13 April 2004.

Less than 10% hydrolysis of the test item occurred over a 120 -hour period, equivalent to a half-life greater than 1 year at 25°C.

The estimated half-lives at 25°C of the test item are:

pH

Estimated half-life at 25°C

4

>1 year

7

>1 year

9

>1 year