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Hydrolysis

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Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Experimental starting date: 27 March 2017 Experimental completion date: 06 April 2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
The sample solutions were taken from the waterbath at various times and the pH of each solution recorded.
The concentration of the sample solution was determined by high performance liquid chromatography (HPLC).
Buffers:
Plase see section below "Any other information on materials and methods, incs. table"
Details on test conditions:
Performance of the Test
Preparation of the Test Solutions
Sample solutions were prepared in stoppered glass flasks at a nominal concentration of 1.0 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.
Duration:
144 h
pH:
4
Temp.:
50 °C
Initial conc. measured:
>= 1.02 - <= 1.04 g/L
Duration:
144 h
pH:
7
Temp.:
50 °C
Initial conc. measured:
>= 0.927 - <= 0.96 g/L
Duration:
144 h
pH:
9
Temp.:
50 °C
Initial conc. measured:
>= 0.975 - <= 0.983 g/L
Number of replicates:
2
Positive controls:
no
Negative controls:
yes
Remarks:
Matrix blanks Acetonitrile: relevant buffer (1:1 v/v)
Statistical methods:
Evaluation of Data
The absorbance and concentration of each standard solution were plotted on a calibration curve (first order) and the sample concentrations then interpolated from this curve. The concentrations were then corrected for dilution factor (200).
Preliminary study:
No significant peaks were observed at the approximate retention time of the test item on analysis of any matrix blank solutions.
As the test item was determined to be hydrolytically stable under all conditions (t½ > 1 year at 25 °C), no additional testing was performed.
Test performance:
Validation
The detector response with respect to concentration was assessed over the nominal concentration range of 0.5 to 7.5 mg/L (all pH’s). The results were satisfactory with correlation coefficients (r) of ≥ 1.000 being obtained. The detector response for all pH’s was a quadratic fit, therefore a multi-point calibration was run with each set of samples, using matrix matched standards.
Transformation products:
no
Details on hydrolysis and appearance of transformation product(s):
Substance was detrmined to be hydrolytically stable under all conditions.
Key result
pH:
4
Temp.:
25 °C
Hydrolysis rate constant:
0 h-1
DT50:
> 1 yr
Type:
(pseudo-)first order (= half-life)
Remarks on result:
hydrolytically stable based on preliminary test
Remarks:
Estimated rate constant at 25°C
Key result
pH:
7
Temp.:
25 °C
Hydrolysis rate constant:
0 h-1
DT50:
> 1 yr
Type:
(pseudo-)first order (= half-life)
Remarks on result:
hydrolytically stable based on preliminary test
Remarks:
Estimated rate constant at 25°C
Key result
pH:
9
Temp.:
25 °C
Hydrolysis rate constant:
0 h-1
DT50:
> 1 yr
Type:
(pseudo-)first order (= half-life)
Remarks on result:
hydrolytically stable based on preliminary test
Remarks:
Estimated rate constant at 25°C
Details on results:
Please refer below to "Any other information on results incs. tables"

  Preliminary Test/Tier 1

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

Preliminary Testing pH 4 at 50.0 ± 0.5 °C

Solution

Mean peak area

Standard 0.529 mg/L

3.66 x 105

Standard 1.59 mg/L

1.11 x 106

Standard 2.65 mg/L

1.81 x 106

Standard 3.70 mg/L

2.53 x 106

Standard 4.76 mg/L

3.27 x 106

Standard 5.30 mg/L

3.69 x 106

Standard 5.82 mg/L

3.98 x 106

Standard 6.88 mg/L

4.72 x 106

Standard 7.94 mg/L

5.43 x 106

Initial Sample A, pH 4

3.51 x 106

Initial Sample B, pH 4

3.57 x 106

24 Hour Sample A, pH 4

3.62 x 106

24 Hour Sample B, pH 4

3.57 x 106

120 Hour Sample A, pH 4

3.63 x 106

120 Hour Sample B, pH 4

3.61 x 106

144 Hour Sample A, pH 4

3.71 x 106

144 Hour Sample B, pH 4

3.70 x 106

Preliminary Testing pH 7 at 50.0 ± 0.5 °C

Solution

Mean peak area

Standard 0.569 mg/L

5.06 x 105

Standard 1.71 mg/L

1.47 x 106

Standard 2.84 mg/L

2.34 x 106

Standard 3.98 mg/L

3.25 x 106

Standard 5.12 mg/L

4.04 x 106

Standard 5.01 mg/L

4.03 x 106

Standard 6.27 mg/L

4.98 x 106

Standard 7.39 mg/L

5.82 x 106

Standard 8.53 mg/L

6.60 x 106

Initial Sample A, pH 7

3.86 x 106

Initial Sample B, pH 7

3.73 x 106

24 Hour Sample A, pH 7

3.90 x 106

24 Hour Sample B, pH 7

3.95 x 106

120 Hour Sample A, pH 7

3.86 x 106

120 Hour Sample B, pH 7

3.84 x 106

144 Hour Sample A, pH 7

3.92 x 106

144 Hour Sample B, pH 7

3.95 x 106

Preliminary Testing pH 9 at 50.0 ± 0.5 °C

Solution

Mean peak area

Standard 0.511 mg/L

4.28 x 105

Standard 1.53 mg/L

1.27 x 106

Standard 2.55 mg/L

2.08 x 106

Standard 3.58 mg/L

2.88 x 106

Standard 4.60 mg/L

3.67 x 106

Standard 5.18 mg/L

4.00 x 106

Standard 5.62 mg/L

4.42 x 106

Standard 6.64 mg/L

5.09 x 106

Standard 7.66 mg/L

5.75 x 106

Initial Sample A, pH 9

3.85 x 106

Initial Sample B, pH 9

3.87 x 106

24 Hour Sample A, pH 9

3.75 x 106

24 Hour Sample B, pH 9

3.86 x 106

120 Hour Sample A, pH 9

3.94 x 106

120 Hour Sample B, pH 9

3.93 x 106

144 Hour Sample A, pH 9

3.85 x 106

144 Hour Sample B, pH 9

3.97 x 106

 

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

pH 4 at 50.0 ± 0.5 ºC

Time (Hours)

Concentration (g/L)

% of mean initial concentration

A

B

A

B

0

1.02

1.04

-

-

24

1.05

1.04

102.5

100.8

120

1.06

1.05

102.8

102.0

144

1.08

1.08

105.0

104.6

 

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

pH 7 at 50.0 ± 0.5 ºC

Time (Hours)

Concentration (g/L)

% of mean initial concentration

A

B

A

B

0

0.960

0.927

-

-

24

0.972

0.983

103.0

104.2

120

0.961

0.954

101.9

101.2

144

0.976

0.984

103.5

104.3

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

pH 9 at 50.0 ± 0.5 ºC

Time (Hours)

Concentration (g/L)

% of mean initial concentration

A

B

A

B

0

0.975

0.983

-

-

24

0.949

0.978

96.9

99.9

120

1.00

0.999

102.3

102.0

144

0.976

1.01

99.7

103.2

 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 test item was determined to be hydrolytically stable under all conditions (t½ > 1 year at 25 °C).
Executive summary:

The abiotic degradation, hydrolysis as a function of pH of COOLACT 10 was carried out using a procedure designed to be compatible with Method C.7 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 and REACH Regulation (EC) No 1907/2006 of the European Parliament and of the Council of 18 December 2006. The results are as follows:

pH

Half-Life at 25 °C

4

>1 year

7

>1 year

9

>1 year

Description of key information

No significant peaks were observed at the approximate retention time of the test item on analysis of any matrix blank solutions.

As the test item was determined to be hydrolytically stable underallconditions (t½ > 1 year at 25 °C), no additional testing was performed.

Key value for chemical safety assessment

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

Additional information

The estimated rate constant and half-life at 25 °C of the test item are shown in the following table:

pH

Estimated rate constant (hr-1) at 25°C

Half-life at 25 °C

4

-

> 1 year

7

-

> 1 year

9

-

> 1 year

 

 

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