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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:
22 February 2006 to 10 July 2006
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)
Specific details on test material used for the study:
Identity: FAT 40824/A
Batch: Red ROE 805 BOP 04/05
Appearance: dark red powder
Purity: Organic part (Na-salt): approx. 82 %; Main component 1 : approx. 36.2 %; Main component 2: approx. 27.5 %; Oligomers: 10%
Expiration date: 01 October 2010
Storage: At room temperature at about 20°C in a desiccator (hygroscopic)
Radiolabelling:
not specified
Analytical monitoring:
yes
Details on sampling:
Before and after incubation, 50 µl aliquots of the test solutions at each pH value were analysed without dilution by measuring the UV signal of FAT 40824/A after HPLC separation of the injected sample solution.
Buffers:
Buffer pH 4, Biphthalate
Buffer pH 7, Phosphate
Buffer pH 9, Borate
Details on test conditions:
All glassware, which must be inert in the pH range applied, was rinsed with sterile buffer. The hydrolysis was carried out in flasks, which were stoppered or sealed with an inert material (glass).
Duration:
120 h
pH:
4
Temp.:
50 °C
Duration:
92.8 h
pH:
7
Temp.:
30 °C
Duration:
23.3 h
pH:
7
Temp.:
40 °C
Duration:
7 h
pH:
7
Temp.:
50 °C
Duration:
159.3 h
pH:
9
Temp.:
50 °C
Duration:
66.67 h
pH:
9
Temp.:
60 °C
Duration:
8.8 h
pH:
9
Temp.:
80 °C
Number of replicates:
Two aliquots of this test solution of approximately 50 ml each were transferred into 50 ml Erlenmeyer flasks in order to perform a duplicate test.
Positive controls:
no
Negative controls:
no
Statistical methods:
The logarithms of the concentrations were plotted against time (log10 (ct)). If the plot was a straight line, the rate constant and the halflive
time was then calculated using the slope. Otherwise, the rate constant could be estimated by the use of the Arrhenius relationship.
Preliminary study:
Due to the instability of the test item found in the preliminary test at 50.0 °C, further hydrolysis tests were performed at 50 °C, 40 °C and 30 °C in the buffered test solution at pH 7.0 and at 50 °C, 60 °C and 80 °C in the buffered test solution at pH 9.0.
At pH 4.0 the test item was found to be stable at 50 °C. Therefore, no further testing was performed at this pH-value.
Transformation products:
not specified
pH:
7
Temp.:
25 °C
Hydrolysis rate constant:
0 s-1
DT50:
90 h
Type:
(pseudo-)first order (= half-life)
pH:
7
Temp.:
30 °C
Hydrolysis rate constant:
0 s-1
DT50:
44 h
Type:
(pseudo-)first order (= half-life)
pH:
7
Temp.:
40 °C
Hydrolysis rate constant:
0 s-1
DT50:
15 h
Type:
(pseudo-)first order (= half-life)
pH:
7
Temp.:
50 °C
Hydrolysis rate constant:
0 s-1
DT50:
4 h
Type:
(pseudo-)first order (= half-life)
pH:
9
Temp.:
25 °C
Hydrolysis rate constant:
0 s-1
DT50:
2 530 h
Type:
second order
pH:
9
Temp.:
50 °C
Hydrolysis rate constant:
0 s-1
DT50:
98 h
Type:
second order
pH:
9
Temp.:
60 °C
Hydrolysis rate constant:
0 s-1
DT50:
31 h
Type:
second order
pH:
9
Temp.:
80 °C
Hydrolysis rate constant:
0 s-1
DT50:
4 h
Type:
second order

The results are summarised below (the values typed in italics were calculated using the Arrhenius equation):

pH

Temperature [°C]

Reaction rate

Constant k

[1/hours]

Reaction rate

Constant k [1/s]

Half-life time

t1/2 [hours]

7.0

25

7.70x 10-3

2.14 x 10-6

90

50

1.73 x10-1*

4.82 x10-5

4

40

4.50x10-2*

1.25 x10-5

15

30

1.57x10-2*

4.35 X10-6

44

9.0

25

2.74 x10-4

7.61 x 10-8

2530

50

7.08x10-3*

1.97 x10-5

98

60

2.22x10-2*

6.17 x10-5

31

80

1.89x10-1*

5.25 x10-5

4

 

* The tabulated value is the mean of two samples.

FAT 40824/A is stable at pH 4.0. Its half-life is longer than one year at 25°C.

The first peak of FAT 40824/A at pH 7.0 has a half-life of 90 hours (4 days) at 25°C.

The second peak of FAT 40824/A at pH 9.0 has a half-life of 2530 hours (105 days) at 25°C.

Validity criteria fulfilled:
yes
Conclusions:
FAT 40824/A is stable at pH 4.0. Its half-life is longer than one year at 25 °C.
The first peak of FAT 40824/A at pH 7.0 has a half-life of 90 hours (4 days) at 25 °C.
The second peak of FAT 40824/A at pH 9.0 has a half-life of 2530 hours (105 days) at 25 °C.
Executive summary:

In a GLP compliant study, the hydrolysis behaviour of FAT 40824/A in aqueous buffered solutions adjusted to pH 4.0, pH 7.0 and pH 9.0. is determined according to OECD Guideline for Testing of Chemicals No. 111, adopted May 12, 1981 and EEC Directive 92/69, Section C.7, L383 A, December 1992.

FAT 40824/A was found to be stable at pH 4.0 at 50°C. Therefore, no further testing was performed at this pH-value. At pH 7.0 and pH 9.0 a specific degradation behaviour was observed. The test item consists of two main components.

At pH 7.0, the first test item peak (retention time at about 17 minutes) decreases and the second test item peak (retention time at about 19 minutes) was stable. The first test item peak was not stable at pH 7.0, further testing was performed at lower temperatures in order to calculate the rate constant (K25) and the half-life of the hydrolysis at pH 7.0 and 25°C.

At pH 9.0 the first peak test item peak increased and the second decreased simultaneously. As FAT 40824/A at pH 9.0 was not stable, further testing was performed at elevated temperatures and observing the second peak in order to calculate the rate constant (k25) and the half-life of the hydrolysis at pH 9.0 and 25°C.

The first peak of FAT 40824/A at pH 7.0 has a half-life of 90 hours (4 days) at 25 °C. The second peak of FAT 40824/A at pH 9.0 has a half-life of 2530 hours (105 days) at 25 °C.

Description of key information

The half-life for hydrolysis have been determined at 25 °C as follows:
> 1 year at pH 4.0
90 hours (4days) at pH 7.0
2530 hours (105 days) at pH 9.0

Key value for chemical safety assessment

Half-life for hydrolysis:
90 h
at the temperature of:
25 °C

Additional information

The hydrolysis behaviour of FAT 40824/A in aqueous buffered solutions adjusted to pH 4.0, pH 7.0 and pH 9.0. is determined according to OECD Guideline for Testing of Chemicals No. 111, adopted May 12, 1981 and EEC Directive 92/69, Section C.7, L383 A, December 1992.

The results show that FAT 40824/A is stable at pH 4.0. Its half-life is longer than one year at 25 °C. The first peak of FAT 40824/A at pH 7.0 has a half-life of 90 hours (4 days) at 25 °C. The second peak of FAT 40824/A at pH 9.0 has a half-life of 2530 hours (105 days) at 25 °C.