1,7-Naphthalenedisulfonic acid, 2-[[4-chloro-6-(cyanoamino)-1,3,5-triazin-2-yl]amino]-5-hydroxy-6-[2-[2-methoxy-5-[[2-(sulfooxy)ethyl]sulfonyl]phenyl]diazenyl]-, lithium sodium salt (1:?:?)

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From Jun. 11, 1999 to Dec. 14, 1999

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

Principles of method if other than guideline:

Not applicable

GLP compliance:

yes

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

- Sampling method:
Preparation of Test Samples: Solutions of the test substance were prepared by weighing between 10 and 15 mg of the test substance in a 50 mL volumetric flask and dissolving in the relevant buffer. The resulting solution was subjected immediately to the hydrolysis procedure.
Preparation of the Standards: The calculation standards were freshly prepared by weighing between 7 and 16 mg of the standard test substance in a 50 mL volumetric flask and dissolving in the buffer pH 4 7 or 9.
- Sample storage conditions before analysis: Not stored

Buffers:

- pH: 4
- Composition of buffer: 21.008 g citric acid monohydrate were dissolved in 200 mL sodium hydroxide solution (c=1 mole/L). This solution was filled up to a volume of 1000 mL with distilled water. 44 mL of hydrochloric acid (c=1 mole/L) were added to 560 mL of this solution and filled up to a volume of 1000 mL with distilled water.

- pH: 7
- Composition of buffer: 13.61 g potassium dihydrogen phosphate were dissolved in 1000 mL distilled water. 29.63 mL of sodium hydroxide solution (c=1 mole/L) were added to 500 mL of this solution and filled up to a volume of 1000 mL with distilled water.

- pH: 9
- Composition of buffer: 7.46 g potassium chloride and 6.184 g boric acid were dissolved in 1000 mL water. 500 mL of this solution were added to 21.3 mL sodium hydroxide (c=1 mole/L) and filled up to a volume of 1000 mL with water.

For performing the hydrolysis the solution was refluxed and the pH value was adjusted to respective pH (4, 7 and 9) for the each hydrolysis temperature.

Details on test conditions:

TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: Flask

Test Procedure
The flask containing the hydrolysis mixture was placed in a thermostatically controlled water bath at the selected temperature for the specified time. Thereafter it was cooled immediately. The pH was controlled.
-Analysis: HPLC analysis of the unhydrolysed test substance (main compound)

OTHER TEST CONDITIONS
- Adjustment of pH: Yes

Duration:

5 d

pH:

4

Temp.:

50 °C

Initial conc. measured:

257.2 - 266.24 mg/L

Duration:

5 d

pH:

7

Temp.:

50 °C

Initial conc. measured:

254.88 - 272.92

Duration:

5 d

pH:

9

Temp.:

50 °C

Initial conc. measured:

263.44 - 265.32

Number of replicates:

Two

Positive controls:

no

Negative controls:

no

Preliminary study:

The decomposition at pH 9 is higher than 50 % after 2.4 h at 50 °C. Thus the test substance may be considered hydrolytically instable at pH 9. According to the guideline a half-life period of less than one day under environmental conditions (25 °C) may be estimated. The pretests at pH 4 and at pH 7 indicate that an examination of the hydrolysis kinetics is essential.

Transformation products:

no

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

Not applicable

pH:

4

Temp.:

25 °C

DT50:

7.95 d

Type:

other: Extrapolated value

Remarks on result:

other: Extrapolation according to the Arrhenius equation

pH:

7

Temp.:

25 °C

DT50:

12.6 d

Type:

other: Extrapolated value

Remarks on result:

other: Extrapolation according to the Arrhenius equation

pH:

4

Temp.:

50 °C

Hydrolysis rate constant:

0.03 h-1

DT50:

22.76 h

Type:

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

Remarks on result:

other: correlation: r = 0.9978

pH:

4

Temp.:

60 °C

Hydrolysis rate constant:

0.068 h-1

DT50:

10.27 h

Type:

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

Remarks on result:

other: correlation: r =0.9998

pH:

4

Temp.:

70 °C

Hydrolysis rate constant:

0.134 h-1

DT50:

5.16 h

Type:

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

Remarks on result:

other: correlation: r = 0.9995

pH:

7

Temp.:

50 °C

Hydrolysis rate constant:

0.061 h-1

DT50:

11.31 h

Type:

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

Remarks on result:

other: correlation: r = 0.9970

pH:

7

Temp.:

60 °C

Hydrolysis rate constant:

0.198 h-1

DT50:

3.5 h

Type:

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

Remarks on result:

other: correlation: r = 0.9998

pH:

7

Temp.:

70 °C

Hydrolysis rate constant:

0.603 h-1

DT50:

1.15 h

Type:

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

Remarks on result:

other: correlation: r = 1.0000

Details on results:

TEST CONDITIONS
- pH, sterility, temperature, and other experimental conditions maintained throughout the study: Yes

Table 1. Summary of the Hydrolysis Results :

Summary and extrapolation of the results at pH 4 and 7

pH	Temperature (°C)	t1/2(by regression) ( h)	Experiment
4	50	22.76	Test 1
4	60	10.27	Test 2
4	70	5.16	Test 3
	25	190.83 h=(7.95 d)	Extrapolation
7	50	11.31	Test 1
7	60	3.50	Test 2
7	70	1.15	Test 3
	25	303.05 h=(12.6 d)	Extrapolation

Validity criteria fulfilled:

yes

Conclusions:

Under the test conditions, the extrapolated half life values of the test substance at pH 4 and 7 were found to be 7.95 and 12.6 d respectively at 25 °C. At pH 9 the decomposition is higher than 50 % after 2.4 h at 50 °C. Thus the test substance may be considered hydrolytically instable at pH 9.

Executive summary:

A study was performed to determine the abiotic degradation of the test substance, i.e. the determination of the hydrolysis rate as a function of the pH-value according to EU Method C.7. in compliance with GLP.

 

Solutions of the test substance were prepared by weighing between 10 and 15 mg of the test substance in a 50 mL volumetric flask and dissolving in the relevant buffer. The resulting solution was subjected immediately to the hydrolysis procedure.

The flask containing the hydrolysis mixture was placed in a thermostatically controlled water bath at the selected temperature for the specified time. Thereafter it was cooled immediately. The pH was controlled. The HPLC analysis of the unhydrolysed test substance (main compound) was performed without any delay

 

At pH 4 the half-life period was determined by extrapolating the results of the experiments at 50, 60 and 70 °C to a temperature of 25 °C. It was found to be 7.95 d.

 

At pH 7 the half-life period was determined by extrapolating the results of the experiments at 50, 60 and 70 °C to a temperature of 25 °C. It was found to be 12.6 d.

 

At pH 9 the decomposition is higher than 50 % after 2.4 h at 50 °C. Thus the test substance may be considered hydrolytically instable at pH 9.

 

Under the test conditions, the extrapolated half life values of the test substance at pH 4 and 7 were found to be 7.95 and 12.6 d respectively at 25 °C.

Description of key information

The extrapolated half life values of test substance at pH 4 and 7 were found to be 7.95 and 12.6 d respectively at 25 °C. At pH 9 the decomposition is higher than 50 % after 2.4 h at 50 °C. Thus the test substance may be considered hydrolytically instable at pH 9

Key value for chemical safety assessment

Half-life for hydrolysis:

7.95 d

at the temperature of:

25 °C

Additional information

A study was performed to determine the abiotic degradation of the test substance i.e. the determination of the hydrolysis rate as a function of the pH-value according to EU Method C.7.

 

Solutions of the test substance were prepared by weighing between 10 and 15 mg of the test substance in a 50 mL volumetric flask and dissolving in the relevant buffer. The resulting solution was subjected immediately to the hydrolysis procedure.

The flask containing the hydrolysis mixture was placed in a thermostatically controlled water bath at the selected temperature for the specified time. Thereafter it was cooled immediately. The pH was controlled. The HPLC analysis of the unhydrolysed test substance (main compound) was performed without any delay

 

At pH 4 the half-life period was determined by extrapolating the results of the experiments at 50, 60 and 70 °C to a temperature of 25 °C. It was found to be 7.95 d.

 

At pH 7 the half-life period was determined by extrapolating the results of the experiments at 50, 60 and 70 °C to a temperature of 25 °C. It was found to be 12.6 d.

 

At pH 9 the decomposition is higher than 50 % after 2.4 h at 50 °C. Thus the test substance may be considered hydrolytically instable at pH 9.

 

The extrapolated half life values of test substance at pH 4 and 7 were found to be 7.95 and 12.6 d respectively at 25 °C. At pH 9 the decomposition is higher than 50 % after 2.4 h at 50 °C. Thus the test substance may be considered hydrolytically instable at pH 9 (Muhlberger B, 1999).