7-acetamido-4-hydroxy-3-[[4-[[2-(sulphooxy)ethyl]sulphonyl]phenyl]azo]naphthalene-2-sulphonic acid, sodium salt

Hydrolysis

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

from 1985-10-01 to 1985-10-29

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

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:

no

Negative controls:

no

Preliminary study:

The substance was unstable at pH 4 and pH 9. At pH 9 the concentration of the substance decreased to < 10 % of the initial value by 2.4 hours. At pH 4 the substance decreased its initial concentration by less than 10 % in less than 5 days.
No further tests were carried out for these pH values. For pH 7 the hydrolysis results were measured at temperatures of 38 and 50 °C.

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:

0.116 h-1

DT50:

6 h

Type:

(pseudo-)first order (= half-life)

pH:

7

Temp.:

38 °C

Hydrolysis rate constant:

0.027 h-1

DT50:

25.7 h

Type:

(pseudo-)first order (= half-life)

Key result

pH:

7

Temp.:

25 °C

Hydrolysis rate constant:

0.005 h-1

DT50:

6 d

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other: A=5284; B=15.4

pH:

4

Temp.:

25 °C

DT50:

> 1 yr

pH:

9

Temp.:

25 °C

DT50:

< 1 d

Details on results:

TEST CONDITIONS
- pH, sterility, temperature, and other experimental conditions maintained throughout the study: yes
- Anomalies or problems encountered: no

MAJOR TRANSFORMATION PRODUCTS
No determined

MINOR TRANSFORMATION PRODUCTS
No determined

MINERALISATION
No determined

INDICATION OF UNSTABLE TRANSFORMATION PRODUCTS:
No

VOLATILIZATION (at end of study)
No

UNIDENTIFIED RADIOACTIVITY
No

Results with reference substance:

No results with reference substance were determined.

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 the hydrolysis study, the half life at 25 °C is > 1 year, 6 days, and < 1 day at pH 4, 7, and 9, respectively.

Executive summary:

The structural analogue 01 as lithium salt was tested by EU method C.7 'Hydrolysis as function of pH' at ph 4, 7 and 9. Based on results of a preliminary study, the half-life at pH 4 and 9 is estimated to be one year and maximum one day, respectively. At pH 7 (measured at at 38 and 50°C) the hydrolysis showed a pseudo-first order curve. The half life at 25°C was calculated to be 6 days (Bartsch 1985).

Reference 2

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

1989

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)

GLP compliance:

yes

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

Sample storage conditions before analysis: inert gas atmosphere; at the dark; the period from dissolution up to the testing at thermostated temeprature was kept as short as possible

Buffers:

- pH: 4, 7, 9
- Composition of buffer:
pH4: potassium hydrogene phthtalate in water; adjustment of the pH by sodium hydroxide
pH7: monopotassium dihydrogene phosphate in water; adjustment of the pH by sodium hydroxide
pH9: boric acid in aqueous potassium chloride solution; adjustment of the pH with sodium hydroxide

Estimation method (if used):

not applicable

Duration:

19 d

pH:

4

Temp.:

60 °C

Initial conc. measured:

209.8 mg/L

Duration:

168 h

pH:

4

Temp.:

70 °C

Initial conc. measured:

211 mg/L

Duration:

71 h

pH:

4

Temp.:

80 °C

Initial conc. measured:

230 mg/L

Duration:

52 h

pH:

7

Temp.:

25 °C

Initial conc. measured:

221 mg/L

Duration:

60 min

pH:

9

Temp.:

20 °C

Initial conc. measured:

226 mg/L

Positive controls:

no

Negative controls:

no

Preliminary study:

at 50°C after 2.4h the following results were observed:
pH4: 1.7% degradation
pH7: 98.9% degradation
pH9: > 99% degradation
at 50°C and pH 4 after 5 d a degradation of 10% was observed

Transformation products:

yes

No.:

#1

No.:

#2

No.:

#2

No.:

#3

Details on hydrolysis and appearance of transformation product(s):

#1: retention time in HPLC: 11.4 minutes: after 2.4 h 75% at 50°C and pH7
#2: retention time in HPLC of both isomers: 8.6 min;
#3: retention time in HPLC: 8.2 min

% Recovery:

33.5

pH:

4

Temp.:

80 °C

Duration:

71.5 h

% Recovery:

42.3

pH:

4

Temp.:

70 °C

Duration:

168 h

% Recovery:

48

pH:

4

Temp.:

60 °C

Duration:

18.98 d

% Recovery:

41.7

pH:

7

Temp.:

25 °C

Duration:

51.9 h

% Recovery:

45.3

pH:

9

Temp.:

20 °C

Duration:

60 min

pH:

4

Temp.:

25 °C

Hydrolysis rate constant:

0 d-1

DT50:

258.5 wk

pH:

7

Temp.:

25 °C

Hydrolysis rate constant:

0.02 d-1

DT50:

> 1 - < 2 d

pH:

9

Temp.:

20 °C

Hydrolysis rate constant:

0.01 min-1

DT50:

48 min

Details on results:

The test substance was determined to be hydrolytically unstable at pH 7 and 9 and hydrolytically stable at pH 4. The t1/2 was determined to be 258.5 weeks at pH4 and 25 °C, 1.9 days at pH7 and 25 °C and 48 minutes at pH9 and 20 °C.

Results with reference substance:

No results with reference substance were determined.

Validity criteria fulfilled:

yes

Conclusions:

Hydrolytically unstable at pH 7 and 9; hydrlotically stable at pH 4. The t1/2 was determined to be 258.5 weeks at pH4 and 25 °C, 1.9 days at pH7 and 25 °C and 48 minutes at pH9 and 20 °C.

Executive summary:

Overall results:

pH	T [°C]	k=<	t1/2
4	25	0.0004 1/d	258.5 weeks
7	25	0.0152 1/d	1.9 days
9	20	0.0146 1/min	48 minutes

 

Description of key information

Based on results of the hydrolysis study, the half life at 25°C is estimated to be > 1 year, 6 days, and < 1 day at pH 4, 7, and 9, respectively.

Key value for chemical safety assessment

Half-life for hydrolysis:

6 d

at the temperature of:

25 °C

Additional information

The structural analogue 01 as lithium salt was tested by EU method C.7 'Hydrolysis as function of pH' at ph 4, 7 and 9. Based on results of a preliminary study, the half-life at pH 4 and 9 is estimated to be one year and maximum one day, respectively. At pH 7 (measured at 38 and 50°C) the hydrolysis showed a pseudo-first order curve. The half-life at 25°C was calculated to be 6 days (Bartsch 1985)

In the preliminary experiments with structural analogue 03 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 72/78. It is reasonable to suppose that the reaction is the same for Reactive Orange 72/78.