2,7-Naphthalenedisulfonic acid, 4-amino-5-hydroxy-, coupled with 3-aminophenol, diazotized 5-amino-2-[(4-aminophenyl)amino]benzenesulfonic acid and diazotized benzenamine, sodium salts

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

March from 12 to 20, 1992

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

according to guideline

Guideline:

other: EEC guideline L251/C.10

Version / remarks:

1984

Principles of method if other than guideline:

Based on OECD guideline 111; only preliminary test.

GLP compliance:

yes

Specific details on test material used for the study:

Evidence of chemical instability: none

Analytical monitoring:

yes

Details on sampling:

Sampling intervals for the parent compound: after 2.4 hours and after 5 days.

Buffers:

Buffer solution pH 4: 0.100 mole acetic acid and 0.100 mole sodium acetate diluted to 1000.0 ml with water and 60 ml 1N Hydrochloric acid.
Buffer solution pH 7: 0.041 mole disodium hydrogen phosphate and 0.028 mole potassium dihydrogen phosphate diluted to 1000.0 ml with water.
Buffer solution pH 9: 0.043 mol disodium tetraborate and 0.017 mole potassium dihydrogen diluted to 1000.0 ml with water.

Details on test conditions:

TEST SYSTEM
- Sterilisation method: the buffer solutions were heated before use at 121 °C for 15 minutes.
- Measures taken to avoid photolytic effects: only brown glass reaction flasks were used.

PREPARATION OF TEST SOLUTIONS
0.2400 - 0.2500 g of the test substance was accurately weighed, dissolved in and diluted to 500.0 ml with water. 10.0 ml of this solution were diluted to 100.0 ml with buffer solutions (pH 4.0, pH 7.0 and pH 9.0) for the preliminary test.

PRELIMINARY STUDY
The hydrolysis was carried out in a thermostatistically controlled water bath at 50 °C.

Duration:

5 d

pH:

4

Temp.:

50 °C

Initial conc. measured:

0.049 - 0.05 g/L

Duration:

5 d

pH:

7

Temp.:

50 °C

Initial conc. measured:

0.049 - 0.05 g/L

Duration:

5 d

pH:

9

Temp.:

50 °C

Initial conc. measured:

0.049 - 0.05 g/L

Number of replicates:

2 replicates per pH.

Positive controls:

no

Negative controls:

no

Preliminary study:

Hydrolysis at pH 7 after 5 days at 50 °C is about 10 %. The substance has a half-life time about one year at 25 °C pH 7.
Degree of hydrolysis of test item at pH 4 and pH 9 after 5 days at 50 °C resulted to be 13.7 % and 36.4 %, respectively. The substance has a half-life time shorter than one year and longer than one day at 25 °C at pH 4 and 9.

Because the substance consists of a very complex mixture of structures, the results of a quantitative evaluation are widely scattered. Changes of the pH-values can affect the different components in various ways, not only by hydrolysis of (a) component (s) but for example also by influencing a protonation equilibrium which can cause changes of the extinction coefficient at a defined wave length.

Transformation products:

not measured

pH:

7

Temp.:

25 °C

Remarks on result:

hydrolytically stable based on preliminary test

The hydrolysis results after 2.4 hours and 5 days, at 50 °C are presented in the tables below.

Preliminary test after 2.4 hours at 50 °C
	pH 4		pH 7		pH 9
Run	1	2	1	2	1	2
Initial conc.  Co (g/l)	0.0493	0.0495	0.0493	0.0495	0.0493	0.0495
Final conc.  Ct (g/l)	0.0492	0.0495	0.0544	0.0512	0.0452	0.0446
100 * (Co-Ct)/Co (%)	0.2	- 0.1	- 10.5	- 3.5	8.2	9.8
Mean value hydrolysis	0.1 %		- 7.0 %		9.0 %
Preliminary test after 5 days at 50 °C
	pH 4		pH 7		pH 9
Run	1	2	1	2	1	2
Initial conc.  Co (g/l)	0.0493	0.0495	0.0493	0.0495	0.0493	0.0495
Final conc.  Ct (g/l)	0.0440	0.0412	0.0441	0.0452	0.0319	0.0310
100 * (Co-Ct)/Co (%)	10.6	16.8	10.4	8.7	35.3	37.4
Mean value hydrolysis	13.7 %		9.6 %		36.4 %

Conclusions:

Hydrolysis at pH 7 after 5 days at 50 °C is about 10 %.; the substance has a half-life time about one year at 25 °C pH 7. The substance has a half-life time shorter than one year and longer than one day at 25 °C at pH 4 and 9.

Executive summary:

The abiotic degradation of the aqueous solutions of the substance was evaluated on the basis of method and procedures outlined for the preliminary test into the OECD guideline 111. Two test solutions were prepared by dissolution of the substance in water and they were further diluted in buffer solutions to obtain six test solutions (in total) of three different pH (4 -7 -9). The hydrolysis was carried out at 50 °C. The concentration of the residual substance was determined by HPLC after 2.4 hours and 5 days. Less than 10 % hydrolysis was observed after 5 days in the test solution of pH 7.0; more than 10 % was hydrolysed in the test solutions of pH 4.0 and pH 9.0. Because the substance consists of a very complex mixture of structures, the results of a quantitative evaluation are widely scattered. Changes of the pH-values can affect the different components in various ways, not only by hydrolysis of (a) component (s) but for example also by influencing a protonation equilibrium which can cause changes of the extinction coefficient at a defined wave length.

Conclusion.

Hydrolysis at pH 7 after 5 days at 50 °C is about 10 %. The substance has a half-life time about one year at 25 °C pH 7. The substance has a half-life time shorter than one year and longer than one day at 25 °C at pH 4 and 9.

Description of key information

Hydrolysis is about 10 % at pH 7 after 5 days at 50 °C. The substance has a half-life time about one year at 25 °C pH 7.

Key value for chemical safety assessment

Half-life for hydrolysis:

1 yr

at the temperature of:

25 °C

Additional information

The abiotic degradation of the aqueous solutions of the substance was evaluated on the basis of method and procedures outlined for the preliminary test into the OECD guideline 111. The concentration of the residual substance was determined by HPLC after 2.4 hours and 5 days. Less than 10 % hydrolysis was observed after 5 days in the test solution of pH 7.0; more than 10 % was hydrolysed in the test solutions of pH 4.0 and pH 9.0. Because the substance consists of a very complex mixture of structures, the results of a quantitative evaluation are widely scattered. Changes of the pH-values can affect the different components in various ways, not only by hydrolysis of (a) component (s) but for example also by influencing a protonation equilibrium which can cause changes of the extinction coefficient at a defined wave length.

Due to the chemical structure and functional groups presents, in the case of Direct Black 168 hydrolysis can be considered as negligible degradation pathway. Hydrolysable organic groups are in fact those groups that can react with water like Esters, Anhydrides, Amides, Carbammates, Nitriles, Cyanates, Epoxides, Halomethanes, Alkylhalides, Urea and none of these groups are present within the commonly market substance formula.