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Environmental fate & pathways

Hydrolysis

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Administrative data

Link to relevant study record(s)

Reference
Endpoint:
hydrolysis
Type of information:
other: read across from supporting substance
Adequacy of study:
key study
Study period:
Since October 1,1985 to October 25,1985
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study without detailed documentation
Qualifier:
according to guideline
Guideline:
EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)
Deviations:
no
GLP compliance:
yes
Radiolabelling:
no
Analytical monitoring:
no
Buffers:
- pH:4, 7 , 9
- Type and final molarity of buffer: 0.05 mol/l
- Composition of buffer:
Buffer solution pH 4: Potassium in dist. water,
(C6H4 (000H) COOK) adjusted = 0.05 mol / l sodium hydroxide added to pH 4.0

Buffer solution pH 7: potassium hydroxide and water,
(KH2P04) = 0.05 mol / l, adjusted to pH 7.0 by sodium hydroxide addition

Buffer solution pH 9 boric acid in aqueous KCl solution
(KCl) = 0.05 mol / l
(H3BO3) = 0.05 mol / l,
adjusted by sodium hydroxide added to pH 9.0
Details on test conditions:
TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: 100 ml flask
- Sterilisation method: yes , boiling glassware for 30 minute and after at 180°C (in oven) for 2 hours

TEST MEDIUM
- Preparation of test medium:
c.a 0.2 ± 1g of item substance was dissolved in 100 ml of buffer (the buffers used was been at an pH=4, pH=7 and pH=9).
In flasks, 10.0 ml of this latter solution were diluited to 100 ml with same buffers (pH 4, 7 and 9).
The flaskes were put in an thermostated bath and before the HPLC analisy, rapidily cooled in an iced bath.



OTHER TEST CONDITIONS
- Adjustment of pH: yes
- concentration was 0.2 ± 1 g / L, on the pure dye converted to about 0.17 g / L, or about 3 x 10^-4 mol / L.
Duration:
5 d
pH:
4
Temp.:
25 °C
Initial conc. measured:
ca. 0.2 g/L
Duration:
5 d
pH:
7
Temp.:
38 °C
Initial conc. measured:
ca. 0.2 g/L
Duration:
5 d
pH:
7
Temp.:
50 °C
Initial conc. measured:
ca. 0.2 g/L
Duration:
5 d
pH:
9
Temp.:
25 °C
Initial conc. measured:
ca. 0.2 g/L
Positive controls:
not specified
Negative controls:
not specified
Transformation products:
no
% Recovery:
ca. 98.5
pH:
4
Temp.:
25 °C
Duration:
ca. 2.4 h
% Recovery:
ca. 98
pH:
4
Temp.:
25 °C
Duration:
ca. 5 d
% Recovery:
ca. 70
pH:
7
Temp.:
25 °C
Duration:
ca. 2.4 h
% Recovery:
< 1
pH:
7
Temp.:
25 °C
Duration:
ca. 5 d
% Recovery:
< 1
pH:
9
Temp.:
25 °C
Duration:
ca. 2.4 h
% Recovery:
< 1
pH:
9
Temp.:
25 °C
Duration:
ca. 5 d
pH:
7
Temp.:
50 °C
Hydrolysis rate constant:
ca. 0.116 h-1
DT50:
ca. 6 h
Type:
(pseudo-)first order (= half-life)
pH:
7
Temp.:
38 °C
Hydrolysis rate constant:
ca. 0.027 h-1
DT50:
ca. 25.7 h
Type:
(pseudo-)first order (= half-life)

log K= -A/T + B

A= 5284

B=15.4

Kobs= 0.0049 h^-1

t1/2(ph7) at 25°C ~ 6 d

test 1 (50°C, pH=7)

time c (0) c (t) c(t)/c(0)  - Log c(t)/c(0)
2 0.2001 0.1583 0.7909 0.1019
3 0.2001 0.1413 0.7062 0.1511
4 0.2001 0.1261 0.6304 0.2004
6 0.2001 0.1007 0.5035 0.298
8 0.2001 0.079 0.3949 0.4035

test 3 (38°C, pH=7)

time c (0) c (t) c(t)/c(0)  -Log c(t)/c(0)
1.33 0.201 0.192 0.9551 0.01995
21 0.2 0.1136 0.5681 0.2455
24 0.2006 0.1034 0.5155 0.2878
27 0.2006 0.0968 0.4825 0.3165
31 0.2006 0.0877 0.437 0.3595
Validity criteria fulfilled:
yes
Conclusions:
Based on results of test item at pH 4,7(at 38 and 50°C) and 9 ,the substance has a t1/2 of about 6 days at 25°C
Executive summary:

The substance is tested by EU method C.7 hydrolisis as function of pH. The substance has been tested at ph buffer 4, 7 ,9. Based on results of test item at pH 4, 7(at 38 and 50°C) and 9 , the substance has a calculated t1/2 of about 6 days at 25°C.

Description of key information

EUC7, similar substance 1, DT50 =  6 days at 25°C, pH 7

Key value for chemical safety assessment

Half-life for hydrolysis:
6 d
at the temperature of:
25 °C

Additional information

Reactive Orange 16 similar substance 1 is tested by EU method C.7 hydrolysis as function of pH. The substance has been tested at ph buffer 4, 7 ,9. Based on results of test item at pH 4,7 (at 38 and 50°C) and 9 , the reactive orange 16 had shown a t1/2 of about 6 days at 25°C. (Bartsch 1985)

In the preliminary experiments with similar substance 2 at pH 7 and 50°C , was observed that in 2.4 hours the presence of the vinyl branch "[[4-[[2-(sulphonatooxy)ethyl]sulphonyl]phenyl]azo]" were less than 1%. (Appel 1989) This part of molecule is identical to reactive orange 16 and reactive orange 16 similar substance 1, in fact the two reactive orange 16 differ only for the counter ionic part (Lithium versus Sodium), this difference has no influence on the hydrolysis pathway. It is reasonable to suppose that the reaction is the same for reactive orange 16.