reaction mass of: 7-amino-3,8-bis-[4-(2-sulfoxyethylsulfonyl)phenylazo]-4- hydroxynaphthalene-2-sulfonic acid, Na/K salt; 7-amino-3-[4-(2-sulfoxyethylsulfonyl)phenylazo]-4-hydroxy-8-[4-(2-sulfoxyethylsulfonyl)-2- sulfophenylazo]naphthalene-2-sulfonic acid, Na/K salt; 7-amino-8-[4-(2-sulfoxyethylsulfonyl)-phenylazo]-4-hydroxy-3-[4-(2-sulfoxyethylsulfonyl)- 2-sulfophenylazo]naphthalene-2-sulfonic acid, Na/K salt; 7-amino-3,8-bis-[4-(2-sulfoxyethylsulfonyl)-2-sulfophenylazo]-4-hydroxynaphthalene-2- sulfonic acid, Na/K salt

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

16.09.1998 to 02.02.1999

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:

not specified

Qualifier:

according to guideline

Guideline:

EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)

GLP compliance:

yes (incl. QA statement)

Remarks:

Swiss GLP

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: TVR50
- Expiration date of the lot/batch: September 1, 2004

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: in a closed bottle at room temperature

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

The test substance is dissolved in aqueous buffer solution, the temperature and the pH are checked at pH 4, 7 and 9 respectively. The decrease of the concentration with time is determined by HPLC. In case of hydrolysis, the logarithms of the concentration are plotted as a function of time, and if the result is a straight line, the reaction is considered to be of (pseudo-)first order. The rate constant and the half-life period are calculated using the slope of the line. When it is not practical to determine a rate constant directly at 25 °C, the half-life period can usually be estimated using the Arrhenius equation.
Calibration solution: A calibration solution (pH4 Code P07 = pH value at which test substance is stable during test time) was prepared (immediately before use), which had approximately the same concentration of buffer as the corresponding test solutions (see working method AAK 6/98).
Calibration solution: 0.6900 to 0.7100 g test substance is accurately weighed, dissolved in and diluted to 100.0 ml with buffer solution pH 4 (= stock solution 1). Calibration solution (VL1) corresponding to the test solution at pH 4: 10.0 ml stock solution 1 in a 100 ml measuring flask are diluted and filled up to the mark with buffer solution pH 4.
Solution for measurement:
20.0 ml of this solution in a 50 ml measuring are diluted and filled to the mark with buffer solution pH 4. A control solution for the calibration solution is prepared with the same range of weighed sample. The calibration solution is prepared just before use.
Test solutions: Three test solutions are prepared as follows: 0.6900 to 0.7100 g test substance is accurately weighed, dissolved in and diluted to 100.0 ml with water (= stock solution 2). Solution for hydrolysis period (PL1): 10.0 ml stock solution 2 are diluted with the buffer solutions pH 4, pH 7, pH 9 respectively in a 100 ml measuring flask and filled up to the mark. Only brown volumetric flasks are used. The flasks are previously rinsed with nitrogen for 5 minutes.

Buffers:

pH 4.0: Novartis Code No. P06: 0.05 mole potassium hydrogen phtalate diluted to 1000 ml with water.
pH 4.0: Novartis Code No. P07: 0.1 mole acetic acid + 0.1 mole sodium acetate diluted to 1000 ml with water + 60.0 ml 1.0 N HCl.
pH 7.0: Novartis Code No. P10: 0.041 mole disodium hydrogen phosphate + 0.028 mole potassium dihydrogen phosphate diluted to 1000 ml with water.
pH 9.0: Novartis Code No. P12: 0.043 mole disodium tetraborate + 0.017 mole potassium dihydrogen phosphate diluted to 1000 ml with water.

Duration:

3.33 h

pH:

7

Temp.:

50 °C

Initial conc. measured:

0.28 g/L

Duration:

3.33 h

pH:

7

Temp.:

50 °C

Initial conc. measured:

0.28 g/L

Duration:

43 h

pH:

7

Temp.:

25 °C

Initial conc. measured:

0.282 g/L

Duration:

43 h

pH:

7

Temp.:

25 °C

Initial conc. measured:

0.28 g/L

Number of replicates:

2

Positive controls:

no

Negative controls:

no

Preliminary study:

Preliminary test results :
At 50 °C and pH 9, the test substance hydrolyses more than 50% in 2.4 hours
At 50 °C and pH 7, the test substance hydrolyses more than 10% in 5 days.
For this reason the hydrolysis is examined at pH 7.

Transformation products:

not specified

pH:

7

Temp.:

25 °C

Hydrolysis rate constant:

0.3 s-1

DT50:

64.3 h

Remarks on result:

other: extrapolated

pH:

7

Temp.:

50 °C

Hydrolysis rate constant:

8.133 s-1

DT50:

2.4

 

pH	temperature   (^0C)	starting concentration Co (g/l)	Reaction rate constant kobsx 100*000 (1/s)	Half life Period t1/2   (h)	correlation factor   r^2
7	50	0.28036	8.068	2.4	0.989103
	50	0.28012	8.197	2.3	0.990859
	mean value		8.133	2.4
	25^1)	0.28164	0.2999	64.2	0.999773
	25^1)	0.28036	0.2993	64.3	0.998916
	mean value		0.2996	64.3
	25^2)		0.2996	64.3

¹⁾measured;²⁾extrapolated

The reaction rate constant at pH7 (25°C) is 2.996E-06 (1/s)

The half life period = 64.3 h = ca. 2.7 days.

Validity criteria fulfilled:

yes

Conclusions:

At 25 °C, Reactive Brown 49 is stable at pH 4 with a half-life period greater than one year; while at pH 7 it has a half-life period of 64.3 h (about 2.7 days). It is unstable at pH 9 with half-life period shorter than one day.

Executive summary:

The test was carried out with FAT 40571/A according to OECD 111 guideline. One test was performed for pH 7 at 50°C while another was performed for pH 7 at 25°C. Aliquots of the test solution standing in the constant-temperature water bath were taken. The concentrations of these samples were determined by HPLC.

Based on the study results following hydrolysis results for FAT 40571/A were observed.

- is stable at pH 4. Its half-life period is longer that one year at 25 °C.

- at pH 7 has a half-life period of 64.3 h (about 2.7 days) at 25 °C.

- is unstable at pH 9. Its half-life period is shorter that one day at 25 °C.

Description of key information

At 25 °C, Reactive Brown 49 is stable at pH 4 with a half-life period greater than one year; while at pH 7 it has a half-life period of 64.3 h (about 2.7 days). It is unstable at pH 9 with half-life period shorter than one day.

Key value for chemical safety assessment

Half-life for hydrolysis:

64.3 h

at the temperature of:

25 °C

Additional information

The test was carried out with Reactive Brown 49 according to OECD 111 guideline. One test was performed for pH 7 at 50°C while another was performed for pH 7 at 25°C. Aliquots of the test solution standing in the constant-temperature water bath were taken. The concentrations of these samples were determined by HPLC.