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Hydrolysis

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Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
16 September to 28 October, 2011
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Followed accepted guideline and GLP requirements
Reference:
Composition 1
Qualifier:
according to
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
GLP compliance:
yes (incl. certificate)
Test material information:
Composition 1
Analytical monitoring:
yes
Details on sampling:
- Sampling intervals for the parent/transformation products: pH 4: 0, 24, and 120 hours; pH 7: 0, 24, 120, and 143 hours; pH 9: 0, 24, 120.5 and 144 hours
- Sampling method: Sample solutions taken from waterbath at various times
- Sampling intervals/times for pH measurements: Same as sampling intervals
- Sample storage conditions before analysis: sheltered from light
- Other observation, if any (e.g.: precipitation, color change etc.): none noted
Buffers:
Buffer Solution Specifications:
Buffer Solution pH Components Concentration (mmol dm^-3)
4 Citric acid 6
Sodium chloride 4
Sodium hydroxide 7
7 Disodium hydrogen orthophosphate(anhydrous) 3
Potassium dihydrogen orthophosphate 2
Sodium chloride 2
9 Disodium tetraborate 1
Buffer solutions were filtered through a 0.2 um membrane filter to ensure sterility. Solutions were subjected to ultrasonication and degassing with nitrogen to minimize dissolved oxygen content
Details on test conditions:
Sample solutions were prepared in stoppered glass flasks at nominal concentrations of 50 mg/l in the three buffer solutions (pH 4, 7 and 9). A 1% co-solvent of acetone was used to facilitate solubility. Samples were maintained in a waterbath at 50 degrees C +/- 0.5 degrees C. Analysis of the solutions was by gas chromatography. Standards were prepared in acetone, with the relevant buffer solution at 4:1 v/v) at nominal concentration of 10 mg/l. Matrix blanks were acetone/relevant buffer (4:1 v/v).

TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: stoppered glass flasks
- Lighting: Normal laboratory lighting
- Measures taken to avoid photolytic effects: samples shielded from light
- Measures to exclude oxygen: buffers degassed with nitrogen
- Details on test procedure for unstable compounds: traces observed for peaks at retention times not of the parent compound
- If no traps were used, is the test system closed/open: pH 9 testing used sealed headspace vials (with minimum headspace) to minimize evaporation
- Is there any indication of the test material adsorbing to the walls of the test apparatus? None observed
Duration:
120 h
pH:
4
Initial conc. measured:
>= 0.043 - < 0.049 g/L
Duration:
143 h
pH:
7
Initial conc. measured:
>= 0.035 - <= 0.041 g/L
Duration:
144 h
pH:
9
Initial conc. measured:
>= 0.051 - <= 0.051 g/L
Number of replicates:
Two replicates per time point per pH; matrix blank
Statistical methods:
Calculations:

The mean peak area of both standards was corrected to a nominal concentration of 10 mg/l and the mean value taken.

The sample solution concentration (g/l) was calculated as:
Cspl = [Pspl/Pstd] x Cstd x D x 1/1000

Cspl = Sample concentration (gm/l)
Pspl = Mean peak area of sample solution
Pstd = Mean peak area of standard solution, corrected to nominal standard solution
Cstd = Nominal standard concentration (10 mg/l)
D = sample dilution factor (5)
Preliminary study:
Preliminary study was only study conducted as material shown to be stable under test conditions
Transformation products:
no
pH:
4
Temp.:
25 °C
Half-life:
> 1 yr
pH:
7
Temp.:
25 °C
Half-life:
> 1 yr
pH:
9
Temp.:
25 °C
Half-life:
> 1 yr
Details on results:
TEST CONDITIONS
- pH, sterility, temperature, and other experimental conditions maintained throughout the study: Yes
- Anomalies or problems encountered (if yes): Findings for preliminary test at pH 9 suggested slow hydrolysis. However, as the material was a diamine, it was expected to be stable. Thus, as the test item was slightly volatile, it was possible that a small amount of test item was lost slowly over time due to evaporation. Therefore, it was decided to carry out the pH 9 testing using sealed headspace vials with minimum headspace.

MAJOR TRANSFORMATION PRODUCTS: See results tables for concentrations in both replicates per time per pH and the corresponding % of mean intial concentration values
At pH4:
At the end of the study period (120 hours), the corresponding concentrations were 112% and 115 % of the applied amount, for replicates A and B respectively.

At pH7:
At the end of the study period (143 hours), the corresponding concentrations were 137% and 139 % of the applied amount, for replicates A and B respectively.

At pH9:
At the end of the study period, the corresponding concentrations were 96.9% and 98.5 % of the applied amount, for replicates A and B respectively.


pH 4 at 50.0 degrees C +/- 0.5

Time (Hours)

Concentration

Log10 [concentration g/l)]

% mean initial concentration

A

B

A

B

A

B

0

4.30 x 10-2

4.87 x 10-2

-1.37

-1.31

-

-

24

5.07 x 10-2

4.48 x 10-2

-1.30

-1.35

111

97.7

120

5.26 x 10-2

5.12 x 10-2

-1.28

-1.29

115

112

pH 7 at 50.0 degrees C +/- 0.5

Time (Hours)

Concentration

Log10[concentration g/l)]

% mean initial concentration

A

B

A

B

A

B

0

4.08 x 10-2

3.48 x 10-2

-1.39

-1.46

-

-

24

5.16 x 10-2

4.17 x 10-2

-1.29

-1.38

136

110

120

4.74 x 10-2

5.04 x 10-2

-1.33

-1.30

125

133

143

5.24 x 10-2

5.17 x 10-2

-1.28

-1.29

139

137

pH 9 at 50.0 degrees C +/- 0.5

Time (Hours)

Concentration

Log10[concentration g/l)]

% mean initial concentration

A

B

A

B

A

B

0

5.05 x 10-2

5.15 x 10-2

-1.30

-1.29

-

-

24

5.02 x 10-2

5.12 x 10-2

-1.30

-1.29

98.4

100

120.5

4.68 x 10-2

4.85 x 10-2

-1.33

-1.32

91.8

98.1

144

5.02 x 10-2

4.94 x 10-2

-1.30

-1.31

98.5

96.9

Validity criteria fulfilled:
yes
Conclusions:
The test item is hydrolytically stable as less than 10% hydrolysis occurrred after 5 days at 50 degrees C, at pH values of 4, 7 and 9. This corresponded to a half-life of greater than 1 year at 25 degrees C.
Executive summary:

In a hydrolysis test as a function of pH, the test article was found to be hydrolytically stable in solution as less than 10% hydrolysis occurred after 5 days when tested at pH values of 4, 7, and 9 at 50 degrees C. Analysis for test item was made using gas chromatography. The corresponding half-life values would be greater than 1 year at 25 degrees C.

Description of key information

Using the OECD guideline N°111 (hydrolysis test as a function of pH), the test article was found to be hydrolytically stable in solution. Indeed, less than 10% hydrolysis occurred after 5 days when tested at pH values of 4, 7, and 9 at 50 degrees C. The analysis of the test item was made using gas chromatography. Such hydrolysis rate gives half-life values greater than 1 year at 25 degrees C.

Key value for chemical safety assessment

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

Additional information