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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:
1998-04-21 to 1998-05-22
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)
GLP compliance:
yes (incl. certificate)
Radiolabelling:
no
Analytical monitoring:
yes
Buffers:
pH 4: 21.008 g citric acid dissolved in 200 ml sodium hydroxide solution (1 mol/l) and filled up to 1 l.
pH 7: 13.61 g potassium dihydrogen phosphate was dissolved in 1L water; 29.63 ml of sodium hydroxide (1 mol/L) were added to 500 ml of this solution and filled up to a volume of 1 L with distilled water. The solution was adjusted to pH 7.0 with sodium hydroxide or hydrochloric acid.
pH 9: 7.46 g of potassium chloride and 6.184 g of boric acid were dissolved in 1 L water; 500 ml of this solution were added to 21.3 ml sodium hydroxide (1 mol/L) and filled up to a volume of 1 L with water. The solution was adjusted to pH 9.0 with sodium hydroxide or hydrochloric acid.
Details on test conditions:
Pre-test
- pH 4, 7, 9 at 50°C
Main Test
-Test 1 - pH7 at 50 °C
-Test 2 - pH7 at 55°C
-Test 4 - pH 7 at 65 °C

Duration:
4.5 h
pH:
7
Temp.:
50
Initial conc. measured:
>= 184.16 - <= 193.76 mg/L
Duration:
3.1 h
pH:
7
Temp.:
55
Initial conc. measured:
>= 173.08 - <= 192.68 mg/L
Duration:
1.6 h
pH:
7
Temp.:
65
Initial conc. measured:
>= 191.64 - < 195.12 mg/L
Number of replicates:
Number of replicates in pre-test - 2 per treatment
Number of replicates in main test - 1 per treatment
Positive controls:
not specified
Negative controls:
not specified
Preliminary study:
The preliminary study indicated the following:
- Decomposition at pH 9 is higher than 50 % after 2.4 hours at 50 °C, indicating the test substance is hydrolytically unstable at pH 9
- Decomposition at pH 4 is less than 10 % after 5 days at 50 °C, indicating the test substance is hydrolytically stable at pH 4
- The pre-test at pH 7 indicated that examination of the hydolysis kinetics is essential
Transformation products:
not measured
Details on hydrolysis and appearance of transformation product(s):
Transformation products were not measured.
pH:
4
Temp.:
25 °C
DT50:
> 1 yr
Remarks on result:
other: Conclusion from preliminary test.
pH:
7
Temp.:
65 °C
Hydrolysis rate constant:
ca. 0.923 h-1
DT50:
ca. 0.75 h
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: r = 0.9998
pH:
7
Temp.:
55 °C
Hydrolysis rate constant:
ca. 0.354 h-1
DT50:
ca. 1.96 h
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: r = 1.0
pH:
7
Temp.:
50 °C
Hydrolysis rate constant:
ca. 0.202 h-1
DT50:
ca. 3.44 h
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: r = 0.996
pH:
7
Temp.:
25 °C
DT50:
59 h
Remarks on result:
other: Extrapolation using the Arrhenius equation
pH:
9
Temp.:
25 °C
DT50:
< 24 h
Remarks on result:
other: Conclusion from preliminary test.

Results of pre-test:

pH

Duration

Decomposition [%]

4

2.4 h

0.7

4

2.4 h

5.5

4

5 d

7.5

4

5 d

6.4

7

2.4 h

33.5

7

2.4 h

35.0

7

5 d

99.5

7

5 d

99.5

9

2.4 h

98.1

9

2.4 h

98.1

9

5 d

99.5

9

5 d

99.6

Validity criteria fulfilled:
yes
Conclusions:
A study was performed to determine abiotic degradation due to hydrolysis as a function of pH of the test substance Reactive Navy FC63805. The study was performed according the EU method C.7 and in compliance with GLP. At pH 4 the decomposition was less than 10 % after 5 days at 50 °C. At pH 7 a half-life of 2.46 days at 25 °C was extrapolated from higher test temperatures. At pH 9 the half-life is < 2.4 hours at 50 °C.
Accordingly, the substance can be considered as hydrolytically stable under acidic (pH 4), moderately degradable at neutral (pH 7), and unstable in basic conditions (pH 9).
Executive summary:

Hydrolysis of the test material was studied in a pre-test and a main test. The experiments were carried out at concentrations of 175 to 200 mg/L in the dark at 50 °C in sterile aqueous buffered solutions at pH 4, 7 and 9 for 5 days in the pre-test and at pH7, at 50, 55 and 65 °C in the main test.

The experiment was conducted in accordance with EU Method C.7 and in compliance with GLP. In the main test the samples were analysed at up to 4.5 hours using HPLC analysis.

The pre-test revealed a pH-dependent decomposition of the substance. At pH 4 after 5 days only 6.4–7.5 % of the substance was decomposed, while at pH 7 and 9 after 5 days almost 100 % of the substance was degraded.

The results of the pre-test triggered more detailed examination of the hydrolysis kinetics. In the main test at pH 7 the half-life period at 25 °C was determined by extrapolating from the results of the experiments at 50, 55 and 65 °C.

The half-lives (DT50, 50% decline times) of the test material at 25 °C was calculated to be > 1 year, 2.46 days and < 1 day at pH 4, 7 and 9 respectively.

This study is classified acceptable and satisfies the guideline requirement for a hydrolysis study.

Description of key information

In a hydrolysis study performed according to EU method C.7 and in compliance with GLP Reactive Navy FC63805 showed variable hydrolytical stability with varying pH:
At pH 7 the half-life period was determined to be 2.46 days by extrapolating the results of the experiments at 25, 50, 55 and 65°C. At pH 4 the substance is considered to be hydrolytically stable (half-life > 1 year). At pH 9 the decomposition was higher than 50 % after 2.4 hours at 50°C. The test substance can be considered as hydrolytically unstable at pH 9.

Key value for chemical safety assessment

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

Additional information

A study was performed to determine the abiotic degradation of the test substance Reactive Navy FC63805. The study was performed according to EU method C.7 and in compliance with GLP.

Two tests were performed, a pre- and a main test. The pre-test revealed a pH-dependent decomposition of the substance. At pH 4 after 5 d only 6.4–7.5 % of the substance was decomposed while at pH 7 and 9 after 5 days almost 100 % of the substance was degraded. The pre-test at pH 7 triggered more detailed examination of the hydrolysis kinetics. At pH 4 the decomposition was < 10 % after 5 days of hydrolysis at 50 °C. At pH 7 the half-life period at 25 °C was determined by extrapolating the results of the experiments at 50, 55 and 65 °C. The DT50 (25 °C) was found to be 59 h. At pH 9 the decomposition was higher than 50 % after 2.4 hours at 50 °C, allowing the conclusion that the substance is hydrolytically unstable at this pH.

The test substance can be considered as hydrolytically unstable at pH 9. The substance can be considered as hydrolytically stable at acidic pH 4. At pH 7 at 25 °C the half-life of the substance was determined to be 59 hours.