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Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Study performed according to guideline and GLP.
Qualifier:
according to
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
GLP compliance:
yes (incl. certificate)
Specific details on test material used for the study:
- Names of test material (as cited in study report): Lemonile; 3,7-dimethyl-2,6-nonadienenitrile
- Substance type: Colourless liquid
- Physical state: Liquid
- Analytical purity: 99.4 % (sum of components)
- Lot No: VE00101509
- Expiration date of the lot/batch: 2012-09-09
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
- Sampling intervals for the parent/transformation products: 0.0, 6.0, 24.0, 120.0, 144.0 h
Buffers:
Ready made concentrates (Titrisol®, MERCK, Darmstadt, Germany) were used to prepare buffer solutions by dilution with fresh ultrapure, sterile water:

pH 4.00 ± 0.02 at 20°C (art. No. 9884): after dilution:

Citric acid: 0.056 mol/l
NaOH: 0.11 mol/l
HCl: 0.044 mol/l

pH 7.00 ± 0.02 at 20°C (art. No. 9887): after dilution

KH2PO4: 0.026 mol/l
Na2HPO4: 0.041 mol/l

pH 9.00 ± 0.02 at 20°C (art. No. 9889): after dilution

H3BO3: 0.05 mol/l
KCl: 0.05 mol/l
NaOH: 0.022 mol/l

In order to avoid any unnecessary excess of inorganic salts that could reduce the solubility of the test substance, these buffer solutions were diluted to 10% with ultrapure water before being used as test media.
Details on test conditions:
TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: 20 ml amber-glass vials (crimp caps with Teflon coated rubber septa)
- Sterilisation method: No special sterilising treatmnet other than heating the glassware to 160°C overnight prior to use was applied.
- Is there any indication of the test material adsorbing to the walls of the test apparatus? No

TEST MEDIUM
- Preparation of test medium: The water solubility of Lemonile at 20°C is 42 mg/l.. According to the guidelines the initial concentration to be used for the hydrolysis reaction should not exceed the half of the saturation concentration, or a concentration of 0.01 mol/l. A nominal concentration of 15.0 mg/l was used in the preliminary test. Therefore, a stock solution containing 15.0 g/l of test substance in acetone was prepared. By a 1:1000 dilution of this solution with buffer solution, the test concentration, 15.0 mg/l, was obtained. The amount of carrier solvent (acetone) did not exceed 0.1%, as required by the guidelines


Duration:
144 h
Preliminary study:
Measured pH values and analytical results are given in Table 1. The criterion given in the guidelines for the preliminary test is:
- If less than 10% degradation after 120h (equivalent to a half-life time higher that 1 year at 25°C) is observed, no further testing is necessary.
This criterion is fulfilled for pH4, pH7 and pH9. For all three pH, < 10% degradation was observed at 50°C over a 138h period (6h to 144h). The concentration was assessed from 6h to 144h since the fast initial drop of concentrations observed during the first 6h of the experiment can be assigned to phenomena other than hydrolysis (adsorption to glassware, septa etc).
Transformation products:
no
% Recovery:
90.2
pH:
4
Temp.:
50 °C
Duration:
138 h
Remarks on result:
other: preliminary test
% Recovery:
95.2
pH:
7
Temp.:
50 °C
Duration:
138 h
Remarks on result:
other: preliminary test
% Recovery:
91.2
pH:
9
Temp.:
50 °C
Duration:
138 h
Remarks on result:
other: preliminary test
Key result
pH:
4
Temp.:
25 °C
DT50:
> 1 yr
Remarks on result:
hydrolytically stable based on preliminary test
Key result
pH:
7
Temp.:
25 °C
DT50:
> 1 yr
Remarks on result:
hydrolytically stable based on preliminary test
Key result
pH:
9
Temp.:
25 °C
DT50:
> 1 yr
Remarks on result:
hydrolytically stable based on preliminary test
Details on results:
TEST CONDITIONS
- pH, sterility, temperature, and other experimental conditions maintained throughout the study: Yes


MAJOR TRANSFORMATION PRODUCTS
At pH4: None identified


At pH7: None identified.


At pH9: None identified.

Table 1

All tabulated values represent rounded-off results obtained by calculations based on the exact raw data.

pH

 

 

 

 

 

t [h]

0.0

6.0

24.0

120.0

144.0

pH4, 50°C

4.00

3.99

3.98

3.97

3.98

 

3.97

3.97

3.98

3.96

3.97

pH7, 50°C

7.02

7.04

7.06

7.06

7.05

 

7.03

7.05

7.06

7.07

7.07

pH9, 50°C

9.01

8.98

8.97

8.97

8.98

 

8.99

8.98

8.96

8.97

8.96

 

Concentrations (aqueous phase): [mg/l]

 

 

 

 

 

t [h]

0.0

6.0

24.0

120.0

144.0

pH4, 50°C

15.4

15.2

14.8

13.9

13.5

 

15.6

15.3

14.9

13.8

13.9

pH7, 50°C

16.0

15.4

15.4

14.0

14.6

 

16.0

15.2

15.3

14.2

14.5

pH9, 50°C

11.7

11.3

11.2

10.5

10.3

 

11.7

11.2

11.2

10.5

10.2

 

Average Concentrations (aqueous phase): [mg/l]

 

 

 

 

 

t [h]

0.0

6.0

24.0

120.0

144.0

pH4, 50°C

15.5

15.2

14.9

13.9

13.7

pH7, 50°C

16.0

15.3

15.3

14.1

14.6

pH9, 50°C

11.7

11.2

11.2

10.5

10.2

 

Average Concentrations (aqueous phase): [%]

 

 

 

 

 

t [h]

0.0

6.0

24.0

120.0

144.0

pH4, 50°C

-

100.0

97.5

91.0

90.2

pH7, 50°C

-

100.0

100.4

92.2

95.2

pH9, 50°C

-

100.0

99.5

93.5

91.2

The criterion given in the guidelines for the preliminary test is:

If less than 10% degradation after 120 h (equivalent to a half-life time higher than 1 year at 25°C) is observed , no further testing is required.

This criterion is fulfilled for pH4, pH7 and pH9. For all three pH < 10% degradation was observed at 50°C over a 138 h period (6 h to 144 h).

The fast initial drop of the concentrations observed during the first 6 h of the experiment can be assigned to phenomena other than hydrolysis (adsorption to glassware, septa etc). Therefore the concentration was assessed from 6 h to 144 h. In this 138 h period less than 10% hydrolysis were observed at all three pH values of 4, 7 and 9. A hydrolysis of less than 10% after 120 h or more at 50°C corresponds to a half-life time of more than one year at 25°C.

Conclusions:
The half-life time of Lemonile at 25°C is higher than one year at pH4, pH7 and pH9.
Executive summary:

An abiotic degradation study (hydrolysis as a function of pH) was carried out with Lemonile according to OECD guideline No 111.

Only the preliminary test needed to be performed since, at 50°C, less than 10% hydrolysis occurred at all three pH values of 4, 7 and 9 after 138h. A hydrolysis of less than 10% after 120h, or more, at 50'C corresponds to a half-life time of more than 1 years at 25'C. C, less than 10% hydrolysis occurred at all three pH values of 4, 7 and 9 after 138h. A hydrolysis of less than 10% after 120h, or more, at 50° C corresponds to a half-life time of more than 1 years at 25°C.

Therefore, the half-life time of Lemonile at 25°C is higher than one year at pH4, pH7 and pH9.

Description of key information

Half life greater than 1 year at 25 °C at pH 4, 7 and 9 (OECD 111)

Key value for chemical safety assessment

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

Additional information

A reliable study was performed in accordance with GLP and OECD Guideline No. 111 to assess the hydrolysis of Lemonile. A nominal concentration of 15 mg/L was used in the preliminary test. The fast initial drop of the concentrations observed during the first 6 h of the experiment can be assigned to phenomena other than hydrolysis (adsorption to glassware, septa etc). Therefore the concentration was assessed from 6 h to 144 h. In this 138 h period less than 10% hydrolysis were observed at all three pH values of 4, 7 and 9. A hydrolysis of less than 10% after 120 h or more at 50 °C corresponds to a half-life time of more than one year at 25°C. The half-life time of Lemonile at 25 °C was therefore found to be greater than one year at pH4, pH7 and pH9.

Since less than 10% degradation was observed in the preliminary test, no further testing was necessary.