Sodium 4-[[3-(acetylamino)phenyl]amino]-1-amino-9,10-dihydro-9,10-dioxoanthracene-2-sulphonate

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2011

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

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

The flasks containing the hydrolysis mixtures were placed in a thermostatically controlled water bath at the selected temperature for the specified time. Thereafter aliquots of each flask were taken and cooled down. The volumetric flasks were flooded with nitrogen again. The aliquots were diluted 0.1 ml to 1 ml with the mobile phase at the beginning of the HPLC-measurement and stored in the refrigerator unto the measurement.
The pH was controlled and the concentration of the unhydrolysed test item (main compound) was measured by HPLC.

The pretests were done at 50°C with buffers at pH 4, 7 and 9.
Tests at pH 7 were performed at 20°C, 40°C and 50°C. At least 6 aliquots were taken between a decomposition rate of 10 and 90%.
Tests at pH 9 were performed at 10°C, 15°C and 20°C. At least 6 aliquots were taken between a decomposition rate of 10 and 90%.


Major hydrolysis products (> 10% of the applied dose) were identified by comparing the retention times of the HPLC chromatograms at same conditions of the hydrolysis products and by-products of Reaktiv Blau 19.

Buffers:

-pH 4:
21.01 g citric acid monohydrate were dissolved in 200 ml sodium hydroxide solution (c = 1 mol/l). This solution was filled up to a volume of 1000 ml with distilled water. 44 ml of hydrochloric acid (c = 1 mol/l) were added to 560 ml of this solution and filled up to a volume of
1000 ml with distilled water. The pH value was adjusted to pH 4 for each hydrolysis temperature.
--pH 7:
13.61 g potassium dihydrogen phosphate were dissolved in 1000 ml distilled water. 30 ml of sodium hydroxide solution (c = 1 mol/l) were added to 500 ml of this solution and filled up to a volume of 1000 ml with distilled water. The pH value was adjusted to pH 7 for each hydrolysis temperature.
-pH 9:
7 .46 g potassium chloride and 6.18 g boric acid were dissolved in 1000 ml distilled water. 21 ml of sodium hydroxide solution (c = 1 mol/l) were added to 500 ml of this solution and filled up to a volume of 1000 ml with distilled water. The pH value was adjusted to pH 9 for each hydrolysis temperature.

Estimation method (if used):

Not conducted.

Details on test conditions:

Choice of Concentration
The optimal concentration of the test item required for the analysis is lower than 6.27 g/l. This value is less than half of the solubility in water (project 20110115.05: c> 220 g/l without correction for the purity) and less than 0.01 mol/l for the test item. This complies with the requirements of the guidelines.

Preparation of the Test Samples
Solutions of the test item were prepared by weighing about 38.2 mg to 58.4 mg of the test item in 50 ml volumetric flasks and dissolving the test item in the relevant buffers (filled up to the mark). This preparation was done in a glove box filled with nitrogen.

Duration:

5 d

pH:

4

Temp.:

50 °C

Initial conc. measured:

815 - 879 mg/L

Duration:

5 d

pH:

7

Temp.:

50 °C

Initial conc. measured:

822 - 824 mg/L

Duration:

5 d

pH:

9

Temp.:

50 °C

Initial conc. measured:

803 - 870 mg/L

Duration:

696.4 h

pH:

7

Temp.:

20 °C

Initial conc. measured:

756 - 834 mg/L

Duration:

77.58 h

pH:

7

Temp.:

40 °C

Initial conc. measured:

790 - 818 mg/L

Duration:

22.45 h

pH:

7

Temp.:

50 °C

Initial conc. measured:

789 - 819 mg/L

Duration:

25.62 h

pH:

9

Temp.:

15 °C

Initial conc. measured:

719 - 737 mg/L

Duration:

7.67 h

pH:

9

Temp.:

20 °C

Initial conc. measured:

1 127 - 1 134 mg/L

Duration:

55.35 h

pH:

9

Temp.:

10 °C

Initial conc. measured:

813 - 822 mg/L

Number of replicates:

2

Positive controls:

no

Negative controls:

no

Statistical methods:

The concentrations of the standards were calculated from the sample weights. The initial concentrations Co of the test item and the concentrations during the test process Ct were calculated from the HPLC software.
In the case of pseudo first order reaction, according to the following relationships a linear dependence on the time (t) is expected for log (Ct/Co): log (Ct/Co) = t * (-kobs) / 2.303
The experimental data of test 1 were checked graphically for the approximate fulfillment of this relationship. The constant kobs was determined by linear regression of - log (Ct/Co) to t.
The half-life period t½ was calculated according to: t½ = In2 / Kobs
The Arrhenius-equation was used to extrapolate the rate constants at higher temperature to room
temperature: In kT = - E/R * 1/T + const.
The constant "E/R" and "const." were determined by linear regression of 1/T to in Kobs

Preliminary study:

The decomposition at pH 9 and pH 7 was above 10% after 5 days at 50°C. The pretests at pH 9 and pH 7 indicate that an examination of the hydrolysis kinetics is essential.
The decomposition at pH 4 is below 10% in 5 days. According to the European Commission Regulation (EC) No. 440/2008 no additional tests have to be performed for pH 4

Test performance:

The test performed within the parameters of the guideline.

Transformation products:

yes

No.:

#1

pH:

4

Temp.:

50 °C

DT50:

> 1 yr

Remarks on result:

other: Hydrolytically stable

pH:

7

Temp.:

25 °C

Hydrolysis rate constant:

0.003 h-1

DT50:

235 h

Remarks on result:

other: extrapolation from 20, 40, 50°C

pH:

9

Temp.:

25 °C

Hydrolysis rate constant:

0.256 h-1

DT50:

2.71 h

Remarks on result:

other: extrapolation from 10, 15, 20°C

pH:

7

Temp.:

20 °C

Hydrolysis rate constant:

0.001 h-1

DT50:

501.6 h

Type:

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

pH:

7

Temp.:

40 °C

Hydrolysis rate constant:

0.025 - 0.025 h-1

DT50:

27.61 - 27.87 h

Type:

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

pH:

7

Temp.:

50 °C

Hydrolysis rate constant:

0.093 - 0.095 h-1

DT50:

7.27 - 7.45 h

Type:

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

pH:

9

Temp.:

10 °C

Hydrolysis rate constant:

0.031 - 0.032 h-1

DT50:

21.81 - 22.13 h

Type:

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

pH:

9

Temp.:

15 °C

Hydrolysis rate constant:

0.068 h-1

DT50:

10.24 h

Type:

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

pH:

9

Temp.:

20 °C

Hydrolysis rate constant:

0.126 - 0.132 h-1

DT50:

5.24 - 5.51 h

Type:

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

Other kinetic parameters:

None measured.

Details on results:

At pH 4 less than 10% of the reaction is observed after 5 days at 50°C (t1/2 > 1 year at 25°C). Thus the test substance may be considered hydrolytically stable and according to the European Commission Regulation (EC) No. 440/2008 no additional testing is required.
At pH 7 the half-life period was determined by extrapolation of the results of the experiments at 20°C, 40°C and 50°C to a temperature of 25°C. lt was found to be 9.8 days.
At pH 9 the half-life period was determined by extrapolation of the results of the experiments at 10°C, 15°C and 20°C to a temperature of 25°C. lt was found to be 0.1 days.
The hydrolysis product was identified as Sodium 1-amino-4-(3-ethenesulfonyl)-phenylamino)-910-dioxo-4a,9,9a,10-tetrahydroanthracene-2-sulfonate.



Validity criteria fulfilled:

yes

Conclusions:

At pH 7 the half-life period was determined by extrapolation of the results of the experiments at 20°C, 40°C and 50°C to a temperature of 25°C. lt was found to be 9.8 days.

At pH 4 less than 10 % of the reaction is observed after 5 days at 50 °C (t y2 at 25 °C > 1 year). Thus the test substance may be considered hydrolytically stable and according to Guideline 67/548/EEC Annex V no additional testing is required.

At pH 9 more than 50 % of the reaction is observed after 2.4 hours at 50 °C. Thus the test substance may be considered hydrolytically unstable and according to Guideline 67/548/EEC Annex V no additional testing is required.

Executive summary:

The objective of this study was the determination of the abiotic degradation of the test item, the determination of the hydrolysis rate as a function of the pH-value according to the consolidated version of Guideline 67/548/EEC Annex V (Council Directive 92/69/EEC) Part C: Methods for determination of ecotoxicity. C.7. abiotic degradation: hydrolysis as a function of pH and OECD test guidelines No. 111 (2004), Hydrolysis as a function of pH. Study performed in accordance with the Principles of Good Laboratory Practice (GLP) and reported with a GLP certificate.

 

At pH 4 less than 10% of the reaction is observed after 5 days at 50°C (t1/2 > 1 year at 25°C). Thus the test substance may be considered hydrolytically stable and according to the European Commission Regulation (EC) No. 440/2008 no additional testing is required.

At pH 7 the half-life period was determined by extrapolation of the results of the experiments at 20°C, 40°C and 50°C to a temperature of 25°C. lt was found to be 9.8 days.

At pH 9 the half-life period was determined by extrapolation of the results of the experiments at 10°C, 15°C and 20°C to a temperature of 25°C. lt was found to be 0.1 days. The hydrolysis product was identified as Sodium 1-amino-4-(3-ethenesulfonyl)-phenylamino)-910-dioxo-4a,9,9a,10-tetrahydroanthracene-2-sulfonate.

Description of key information

Results from the source substance:

 -At pH 4 less than 10% of the reaction is observed after 5 days at 50°C (t1/2 > 1 year at 25°C). Thus the test substance may be considered hydrolytically stable and according to the European Commission Regulation (EC) No. 440/2008 no additional testing is required.

-At pH 7 the half-life period was determined by extrapolation of the results of the experiments at 20°C, 40°C and 50°C to a temperature of 25°C. lt was found to be 9.8 days.

-At pH 9 the half-life period was determined by extrapolation of the results of the experiments at 10°C, 15°C and 20°C to a temperature of 25°C. lt was found to be 0.1 days. The hydrolysis product was identified as Sodium 1-amino-4-(3-ethenesulfonyl)-phenylamino)-910-dioxo-4a,9,9a,10-tetrahydroanthracene-2-sulfonate.

The source substance slowly hydrolyses at higher pH values: the sulfonyl group bond via oxygen transforms into a vinyl group. Since the target substance has no sulfonyl bond via oxygen, no transformation process is expected. The target substance is hydrolytically stable at all pH values.

Key value for chemical safety assessment

Half-life for hydrolysis:

9.8 d

at the temperature of:

25 °C