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Hydrolysis

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Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
From 22 MAR 2004 to 01 APR 2004
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
according to OECD 111
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:
not specified
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
The samples were taken out of the water bath and cooled down to room temperature to stop the hydrolysis reaction. The samples were filtrated and the pH of the clear solutions was measured. All samples were dissolved 1 mL to 10 mL with acetonitrile and then placed into the GC auto sampler for analysis.
Buffers:
- Standard buffer solution pH 4.00, Bernhard Kraft, Art.-No.: 03083.3000, (Citric acid / NaOH / NaCI)
- Standard buffer solution pH 7.00, Riedel-de Haän, Art.-No.: 33546 (KH2PO4 / Na2HPO4) with fungicidal additive
- Standard buffer solution pH 9.00, Riedel-de Haen, Art.-No.: 33548 (Borax / HCI) with fungicidal additive)
Estimation method (if used):
To quantify the degree of degradation of the test substance, the concentration of the degradation product methanol was determined. The aim of his preliminary test was to determine if the degradation of the test item would be below 10% after 5 days at 50 deg C for all tested pH-values (then no further testing required according to the guideline). Therefore it was assumed that for 10% of hydrolysis from one mole of test substance at minimum 0.1 mole of methanol would have to be formed (see table under "Any other information on materials and methods incl. tables").
Details on test conditions:
PREPARATION OF-THE PRELIMINARY TEST SUSPENSIONS
Because of the very low solubility of the test substance in water and due to the fact that no direct quantification of the substance was possible, suspensions of the test substance in the buffer solutions were prepared. Therefore in each case approximately 200 mg of the test substance were mixed with 100 mL of the corresponding buffer solution.
The initial nominal concentrations are given under "Any other information on materials and methods incl. tables".

PERFORMANCE OF THE PRELIMINARY TEST
A sufficient number of vials were filled with each test solution. The vials were closed, packed into small plastic bags to protect them from light, and incubated in a water bath at 50.0°C. According to the sampling schedule below, samples were taken out of the water bath, cooled down to room temperature, filtrated (0.45 µm), diluted 1:10 with acetonitrile and placed in the GC autosampler. All vials were injected twice.

Determination of the degree of degradation: See "Estimation method (if used)"
Duration:
217.5 h
pH:
4
Temp.:
50 °C
Initial conc. measured:
2.235 g/L
Remarks:
the value represents the nominal concentration (4.93 mmol/L)
Duration:
217.5 h
pH:
7
Temp.:
50 °C
Initial conc. measured:
2.024 g/L
Remarks:
the value represents the nominal concentration (4.46 mmol/L)
Duration:
217.5 h
pH:
9
Temp.:
50 °C
Initial conc. measured:
1.849 g/L
Remarks:
the value represents the nominal concentration (4.08 mmol/L)
Number of replicates:
One
Positive controls:
no
Negative controls:
no
Preliminary study:
All measured methanol concentrations were far below the theoretical concentration of methanol expected to evolve after 10% degradation of the test substance. Therefore the submission substance is considered to be stable at normal environmental conditions. The measured degradation of the test substance at pH 4, 7 and 9 at 50°C corresponds to a half-life time of more than one year under outdoor conditions. Therefore no further testing had to be performed at all pH-values.
Transformation products:
no
Details on hydrolysis and appearance of transformation product(s):
No hydrolysis observed.
pH:
4
Temp.:
50 °C
Remarks on result:
hydrolytically stable based on preliminary test
pH:
7
Temp.:
50 °C
Remarks on result:
hydrolytically stable based on preliminary test
pH:
9
Temp.:
50 °C
Remarks on result:
hydrolytically stable based on preliminary test
Details on results:
As in the preliminary study at 50°C at all three pH-values (4.0, 7.0 and 9.0) no hydrolysis was observed (as concluded from the measured methanol concentration, see table under "Any other information on results incl. tables"), the main study did not need to be conducted according to OECD 111.

Results of preliminary test:

Tested
pH
at
50 deg C

Sample
[#]

Duration of
incubation
interval
[h]

Measured
concentration
of methanol
[mg/L]

Hydrolyzed
portion

[%]

pH-value
at 25 deg C

Results

 

Start

0.0

< 1 mg/I

< 1.0

4.0

No further

 

E1

25.3

< 1 mg/I

< 1.0

4.0

testing necessary

4.0

E2

49.5

< 1 mg/I

< 1.0

4.0

degradation <10% (5 days)

 

E3

97.2

< 1 mg/I

< 1.0

4.0

Theoretical Me0H

 

E4

169.3

< 1 mg/I

< 1.0

4.3

concentration at 10%

 

E5

217.5

< 1 mg/I

< 1.0

4.0

degradation = 15.8 mg/L

 

Start

0.0

< 1 mg/I

< 1.0

7.0

No further

 

E1

25.4

< 1 mg/I

< 1.0

7.0

testing necessary

7.0

E2

49.5

< 1 mg/I

< 1.0

7.0

degradation <10% (5 days)

 

E3

97.4

< 1 mg/I

< 1.0

7.0

Theoretical Me0H

 

E4

169.5

< 1 mg/I

< 1.0

7.0

concentration at 10%

 

E5

217.5

< 1 mg/I

< 1.0

7.0

degradation = 14.3 mg/L

 

Start

0.0

< 1 mg/I

< 1.0

9.0

No further

 

E1

25.7

< 1 mg/I

< 1.0

9.0

testing necessary

9.0

E2

49.5

< 1 mg/I

< 1.0

9.0

degradation <10% (5 days)

 

E3

97.5

< 1 mg/I

< 1.0

9.0

Theoretical Me0H

 

E4

169.5

< 1 mg/I

< 1.0

9.0

concentration at 10%

 

E5

217.5

< 1 mg/I

< 1.0

9.0

degradation = 13.1 mg/L

Validity criteria fulfilled:
yes
Conclusions:
In the preliminary study at 50°C and applied buffer pH-values of 4.0, 7.0 and 9.0 no hydrolysis (< 1%) could be observed during the 9 days of the experiment. The submission substance is regarded hydrolytically stable under normal environmental conditions.
Executive summary:

The abiotic degradation of the submission substance was determined according to EU method C.7 and in accordance with OECD-Guideline 111.

The rate of degradation was measured at three different pH-values (4, 7, and 9). At all tested pH values the test substance was stable, this means that the degradation was less than 10 % after 5 days at 50°C. Therefore no further testing was necessary according to the guidelines mentioned above.

Because the test substance is nearly insoluble in aqueous solutions and in common organic solvents, it was impossible to prepare defined solutions. Therefore suspensions of the test substance in the single buffer solutions with a nominal concentration of approximately 2 g/L (4 mmol/L) were prepared.

Due to the test substance properties no analytical method was available for the direct determination of the pigment concentration. Therefore the observation of the degradation progress was achieved by determination of the concentration of methanol, which is the predicted degradation product (ester hydrolysis)

The test suspensions were incubated at 50°C over a period of 217.5 hours (approx. 9 days). Samples were taken from time to time and the methanol concentration was determined by GC-analysis.

All analyzed samples had a methanol concentration below 1 mg/L. This corresponds with a degree of hydrolysis below 1%.

Summing up, the measured results showed that the submission substance is hydrolytically stable at the tested pH-values 4, 7 and 9.

No further testing according to the mentioned guidelines has to be performed.

Endpoint:
hydrolysis
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
see attachment
Reason / purpose for cross-reference:
read-across source
GLP compliance:
not specified
Analytical monitoring:
yes
Duration:
217.5 h
pH:
4
Temp.:
50 °C
Initial conc. measured:
2.235 g/L
Remarks:
the value represents the nominal concentration (4.93 mmol/L)
Duration:
217.5 h
pH:
7
Temp.:
50 °C
Initial conc. measured:
2.024 g/L
Remarks:
the value represents the nominal concentration (4.46 mmol/L)
Duration:
217.5 h
pH:
9
Temp.:
50 °C
Initial conc. measured:
1.849 g/L
Remarks:
the value represents the nominal concentration (4.08 mmol/L)
Number of replicates:
One
Positive controls:
no
Negative controls:
no
Transformation products:
no
Details on hydrolysis and appearance of transformation product(s):
No hydrolysis observed.
pH:
4
Temp.:
50 °C
Remarks on result:
hydrolytically stable based on preliminary test
pH:
7
Temp.:
50 °C
Remarks on result:
hydrolytically stable based on preliminary test
pH:
9
Temp.:
50 °C
Remarks on result:
hydrolytically stable based on preliminary test
Details on results:
As in the preliminary study at 50°C at all three pH-values (4.0, 7.0 and 9.0) no hydrolysis was observed, the main study did not need to be conducted according to OECD 111.
Validity criteria fulfilled:
yes
Conclusions:
In the preliminary study at 50°C and applied buffer pH-values of 4.0, 7.0 and 9.0 no hydrolysis (< 1%) could be observed during the 9 days of the experiment. The submission substance is regarded hydrolytically stable under normal environmental conditions.
Endpoint:
hydrolysis
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
see attachment
Reason / purpose for cross-reference:
read-across source
GLP compliance:
not specified
Analytical monitoring:
yes
Duration:
217.5 h
pH:
4
Temp.:
50 °C
Initial conc. measured:
2.235 g/L
Remarks:
the value represents the nominal concentration (4.93 mmol/L)
Duration:
217.5 h
pH:
7
Temp.:
50 °C
Initial conc. measured:
2.024 g/L
Remarks:
the value represents the nominal concentration (4.46 mmol/L)
Duration:
217.5 h
pH:
9
Temp.:
50 °C
Initial conc. measured:
1.849 g/L
Remarks:
the value represents the nominal concentration (4.08 mmol/L)
Number of replicates:
One
Positive controls:
no
Negative controls:
no
Transformation products:
no
Details on hydrolysis and appearance of transformation product(s):
No hydrolysis observed.
pH:
4
Temp.:
50 °C
Remarks on result:
hydrolytically stable based on preliminary test
pH:
7
Temp.:
50 °C
Remarks on result:
hydrolytically stable based on preliminary test
pH:
9
Temp.:
50 °C
Remarks on result:
hydrolytically stable based on preliminary test
Details on results:
As in the preliminary study at 50°C at all three pH-values (4.0, 7.0 and 9.0) no hydrolysis was observed, the main study did not need to be conducted according to OECD 111.
Validity criteria fulfilled:
yes
Conclusions:
In the preliminary study at 50°C and applied buffer pH-values of 4.0, 7.0 and 9.0 no hydrolysis (< 1%) could be observed during the 9 days of the experiment. The submission substance is regarded hydrolytically stable under normal environmental conditions.

Description of key information

A hydrolysis study according to OECD 111 was performed with C.I. Pigment Yellow 175, which exhibits the highest water solubility within the group of the Acetolone pigments. In addition, there are functional groups (diester) present in the molecule of PY 175, which can be hydrolyzed from a theoretical point of view. PY 175 was stable at all tested pH values

Read-across to PY 180 bulk and nanoform is justified since the water solubility is much lower and there are no ester functions present in the molecule.

Key value for chemical safety assessment

Additional information