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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:
2012
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
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:
The two principle components of the test item were used as tracer peaks for determination of rate of hydrolysis.
GLP compliance:
yes (incl. certificate)
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
OECD Guideline 111 states that the test should be performed at a concentration that will not exceed either 10-2 M of the test substance, or half the saturation concentration. Sponsor supplied information indicates the test item to have a water solubility of >1 g/L. Given the molar mass of the principle components of m/p-Diol is 194 g/mol, the predicted average concentration at 10-2 M was calculated to be ca 1.94 g/L. Therefore the test was performed at ca 0.1 g/L.

Triplicate samples of m/p-Diol, in each of pH 4, 7 and 9 buffers, were prepared on four consecutive time points (5, 1, 0.1 and 0 days prior to analysis). Approximately 100 mg of test item was weighed into a 100 mL volumetric flask and made to volume with Milli-Q water. To separate 15 mL amber, glass bottles were pipetted 1 mL of stock solution. This was performed in triplicate for each pH level at each timepoint.

Sample sets were diluted with 9 mL of respective buffer (pH 4, 7 and 9). The headspace of the test vessels were purged with nitrogen gas then test vessels were capped, sealed with parafilm, shaken thoroughly and placed in a water bath maintained at 50 ± 0.5 °C. Sample sets were kept covered, to avoid photolytic effects, in the water bath for 5, 1, 0.1 and 0 days, respectively.

Following hydrolysis, the pH of each sample was measured and aliquots taken for analysis as described in the analytical method.
Buffers:
Aqueous pH 4 buffer was prepared such that the final solution contained ca 0.4 mM sodium hydroxide and ca 50 mM potassium biphthalate in a 1 L flask. The pH of the buffer used was 3.99. It was purged with nitrogen gas to remove dissolved oxygen.

Aqueous pH 7 buffer solution was prepared such that the final solution contained ca 30 mM sodium hydroxide and ca 50 mM monopotassium phosphate in a 1 L flask. The pH of the buffer used was 6.99. It was purged with nitrogen gas to remove dissolved oxygen.

Aqueous pH 9 buffer solution was prepared such that the final solution contained ca 21 mM sodium hydroxide, ca 50 mM monopotassium chloride and ca 50 mM boric acid in a 1 L flask. The pH of the buffer used was 8.98. It was purged with nitrogen gas to remove dissolved oxygen.
Details on test conditions:
See "details in sampling"
Duration:
5 d
pH:
4
Temp.:
50
Initial conc. measured:
0.1 g/L
Duration:
5 d
pH:
7
Temp.:
50
Initial conc. measured:
0.1 g/L
Duration:
5
pH:
9
Temp.:
50
Initial conc. measured:
0.1 g/L
Number of replicates:
Triplicate samples of m/p-Diol, in each of pH 4, 7 and 9 buffers, were prepared on four consecutive time points (5, 1, 0.1 and 0 days prior to analysis)
Positive controls:
no
Negative controls:
no
Transformation products:
no
% Recovery:
91.4 - 100.3
pH:
4
Temp.:
50 °C
Duration:
0.1 - 5 d
% Recovery:
98.4 - 107.7
pH:
7
Temp.:
50 °C
Duration:
0.1 - 5 d
% Recovery:
97.9 - 107.2
pH:
9
Temp.:
50 °C
Duration:
0.1 - 5 d
pH:
4
Temp.:
50 °C
DT50:
> 1 yr
Type:
not specified
pH:
7
Temp.:
50 °C
DT50:
> 1 yr
Type:
not specified
pH:
9
Temp.:
50 °C
DT50:
> 1 yr
Type:
not specified
Details on results:
Aqueous pH 4 Buffer

The hydrolysis of m/p-Diol was assessed in aqueous pH 4 buffer at 50 ± 0.5 °C. The mean recovery of the applied test item, remaining after 0, 0.1, 1 and 5 days was determined to be 91.4, 100.3, 100.3 and 99.5%, respectively. Therefore, after 5 days the test item was shown to have hydrolysed by less than 10% (equivalent to half-life 25°C >1 year). This indicated that the test item was hydrolytically stable at pH 4 and significant hydrolysis had not occurred.

Aqueous pH 7 Buffer

The hydrolysis of m/p-Diol was assessed in aqueous pH 7 buffer at 50 ± 0.5 °C. The mean recovery of the applied test item, remaining after 0, 0.1, 1 and 5 days was determined to be 98.4, 107.7, 107.4 and 107.7%, respectively. Therefore, after 5 days the test item was shown to have hydrolysed by less than 10% (equivalent to half-life 25°C >1 year). This indicated that the test item was hydrolytically stable at pH 7 and significant hydrolysis had not occurred.

Aqueous pH 9 Buffer

The hydrolysis of m/p-Diol was assessed in aqueous pH 9 buffer at 50 ± 0.5 °C. The mean recovery of the applied test item, remaining after 0, 0.1, 1 and 5 days was determined to be 97.9, 107.2, 106.1 and 100.7%, respectively. Therefore, after 5 days the test item was shown to have hydrolysed by less than 10% (equivalent to half-life 25°C >1 year). This indicated that the test item was hydrolytically stable at pH 9 and significant hydrolysis had not occurred.

Details are shown in tables hereafter.

Hydrolysis of m/p-Diol in Aqueous pH 4 Buffer: Assay of Hydrolysis Samples

 

Time point (Days)

Applied Conc. (μg/mL)

Dilution

Factor

Measured pH

Nominal Conc. (μg/mL)

Determined Conc. (μg/mL)

Recovery

(%)

Mean

Found Recovery (%)

Coefficient

of Variation (%)

Ln of Mean Recovery

Blank

NA

0.8

3.99

0.00

0.00

NA

NA

NA

NA

0

100.00

0.8

0.8

0.8

4.02

4.01

4.01

80.00

80.00

80.00

72.93

73.29

NA*

91.2

91.6

NA*

91.4

NA

4.52

0.1

100.00

0.8

0.8

0.8

4.01

4.02

4.01

80.00

80.00

80.00

79.88

80.42

80.42

99.9

100.5

100.5

100.3

0.4

4.61

1

100.00

0.8

0.8

0.8

4.01

4.00

4.01

80.00

80.00

80.00

80.42

80.12

80.23

100.5

100.2

100.3

100.3

0.2

4.61

5

100.00

0.8

0.8

0.8

4.03

4.04

4.01

80.00

80.00

80.00

78.76

79.25

80.62

98.5

99.1

100.8

99.5

1.2

4.60

NA = Not Applicable

*Not used in further calculations. Bad injection.

 

 

Hydrolysis of m/p-Diol in Aqueous pH 7 Buffer: Assay of Hydrolysis Samples

 

Time point (Days)

Applied Conc. (μg/mL)

Dilution

Factor

Measured pH

Nominal Conc. (μg/mL)

Determined Conc. (μg/mL)

Recovery

(%)

Mean

Found Recovery (%)

Coefficient

of Variation (%)

Ln of Mean Recovery

Blank

NA

0.8

6.99

0.00

0.00

0.0

NA

NA

NA

0

100.0

0.8

0.8

0.8

7.01

6.99

7.00

80.00

80.00

80.00

79.36

79.09

77.65

99.2

98.9

97.1

98.4

1.2

4.59

0.1

100.0

0.8

0.8

0.8

6.97

6.97

6.94

80.00

80.00

80.00

86.96

85.09

86.47

108.7

106.4

108.1

107.7

1.1

4.68

1

100.0

0.8

0.8

0.8

6.94

6.98

6.94

80.00

80.00

80.00

85.30

85.53

87.03

106.6

106.9

108.8

107.4

1.1

 

4.68

5

100.0

0.8

0.8

0.8

6.92

6.94

6.92

80.00

80.00

80.00

86.06

88.72

83.62

107.6

110.9

104.5

107.7

3.0

 

4.68

NA = Not Applicable

 

 

Hydrolysis of m/p-Diol in Aqueous pH 9 Buffer: Assay of Hydrolysis Samples

 

Time point (Days)

Applied Conc. (μg/mL)

Dilution

Factor

Measured pH

Nominal Conc. (μg/mL)

Determined Conc. (μg/mL)

Recovery

(%)

Mean

Found Recovery (%)

Coefficient

of Variation (%)

Ln of Mean Recovery

Blank

NA

0.8

8.98

0.00

0.00

0.0

NA

NA

NA

0

100.0

0.8

0.8

0.8

8.72

8.74

8.74

80.00

80.00

80.00

78.58

78.24

78.16

98.2

97.8

97.7

97.9

0.3

4.58

0.1

100.0

0.8

0.8

0.8

8.74

8.75

8.75

80.00

80.00

80.00

85.48

85.98

85.73

106.9

107.5

107.2

107.2

0.3

4.67

1

100.0

0.8

0.8

0.8

8.75

8.75

8.75

80.00

80.00

80.00

87.07

86.24

81.32

108.8

107.8

101.7

106.1

3.7

4.66

5

100.0

0.8

0.8

0.8

8.75

8.75

8.75

80.00

80.00

80.00

86.66

74.46

NA*

108.3

93.1

NA*

100.7

NA

4.61

NA = Not Applicable

*Not used in further calculations. Bad injection.

 

Validity criteria fulfilled:
yes
Remarks:
see conclusions
Conclusions:
Quality criteria:
* Recovery:
Recoveries should range from 90 % to 110 % for labeled and non-labelled chemicals. In case it is technically difficult to reach this range, a recovery of 70 % for non-labelled chemicals is acceptable, but justification should be given. In the present study, recoveries range between 91 and 108% (Mean Determined Recovery of triplicates)
Executive summary:

The hydrolysis of m/p diol was evaluated in a study performed in accordance with OECD testing guideline 111 and GLP requirements. The two principle components of the test item were used as tracer peaks for determination of rate of hydrolysis.

 

The hydrolysis of m/p-Diol was assessed in aqueous buffers at pH 4, 7 and 9 at 50 ± 0.5 °C. After 5 days the test item was shown to have hydrolysed by less than 10% at each pH (equivalent to half-life 25°C >1 year). This indicated that the test item was hydrolytically stable and significant hydrolysis had not occurred at environmentally relevant pH.

 

Description of key information

m/p-Diol a complex reaction product is regarded as hydrolytically stable. The single component α,α,α',α'-tetramethyl-m-xylene-α,α'-diol (m-diol) is therefore also regarded as hydrolytically stable.

Key value for chemical safety assessment

Additional information

One valid study is available for m/p-Diol, a complex reaction product. The hydrolysis of m/p-Diol was evaluated in a study performed in accordance with OECD testing guideline 111 and GLP requirements. The two principle components of the test item were used as tracer peaks for determination of rate of hydrolysis.

 

The hydrolysis of m/p-Diol was assessed in aqueous buffers at pH 4, 7 and 9 at 50 ± 0.5 °C. After 5 days the test item was shown to have hydrolysed by less than 10% at each pH (equivalent to half-life 25°C >1 year). This indicated that the test item was hydrolytically stable and significant hydrolysis had not occurred at environmentally relevant pH.