Reaction mass of Cobaltate(3-), bis[2-[[[3-[2-[1-[[(2-chlorophenyl)amino]carbonyl]-2-(oxo-κO)propyl]diazenyl-κN1]-4-(hydroxy-κO)phenyl]sulfonyl]amino]benzoato(3-)]-, sodium (1:3) and tetrasodium bis[2-[[[3-[[1-[(2-chloroanilino)carbonyl]-2-oxopropyl]azo]-4-hydroxyphenyl]sulphonyl]amino]benzoato(3-)]cobaltate(4-)

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

28 April, 2014 to 04 September, 2014

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:

no

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

no

Details on sampling:

The test item solutions were prepared by adding 1 mL stock solution into a 100 mL volumetric flask and accurately filled up with the buffer solutions. Under argon atmosphere 2.0 mL of the test item solutions were given into several crimped glass vials. The vials were closed with Teflon sealed screw caps. At the sampling time 2 mL methanol + 1 % phosphoric acid were added (d = 2). The concentration did not exceed 0.01 M or the half saturation concentration. The determined effective concentrations prior to storage at 50 °C were 9.50 mg/L at pH 4, 10.1 mg/L at pH 7 and 10.2 mg/L at pH 9.

Buffers:

The test was carried out at three different pH values: 4.0, 7.0 and 9.0. For this purpose, buffer solutions were prepared using reagent grade chemicals and deionized water. Applicable buffer systems are described in the Appendix of EC method C.7 (92/69/EC), OECD Guideline 111.
The citrate buffer pH 4, the phosphate buffer pH 7 and the borate buffer pH 9 were prepared in a concentration of 0.05 M on the basis of the undissociated acids. The pH value of the buffer solutions used during the test were determined with a calibrated pH meter at the selected temperature with a precision of 0.01 pH units.

Details on test conditions:

Preliminary Test:
A preliminary test was performed at 50±0.5 °C at three pH values: 4.0, 7.0 and 9.0. A sufficient number of measurements were made, in order to be able to estimate whether for each pH value and at 50 °C, the half-life time (t1/2) is less than 10 % of hydrolysis after 120 hours. These values correspond to a half-life time higher than one year under conditions more representative of those of the environment (25 °C).

Hydrolysis of unstable Substances (Tier 2):
The Main Test (Tier 2) was performed at pH 4, 7 and 9. The buffered solution of the test substance was thermostated at 20 °C and 40 °C. To test for first-order behaviour, each reaction solution was analysed in time intervals which provide at least six spaced data points normally between 10 % and 90 % hydrolysis of the substance. Individual replicate test samples (a minimum of duplicate samples contained in separate reaction vessels) were removed and the contents were analysed at each of at least six sampling times (for a minimum of twelve replicate data points). Kinetic analysis for the hydrolysis of unstable substances (Tier 2) was performed and the corresponding DT50 values was calculated. At each sampling date the pH was determined.

Duration:

120 h

pH:

4

Temp.:

50 °C

Initial conc. measured:

9.5 mg/L

Duration:

771 h

pH:

4

Temp.:

40 °C

Initial conc. measured:

10.1 mg/L

Duration:

771 h

pH:

4

Temp.:

20 °C

Initial conc. measured:

10.2 mg/L

Duration:

120 h

pH:

7

Temp.:

50 °C

Initial conc. measured:

10.1 mg/L

Duration:

771

pH:

7

Temp.:

40 °C

Initial conc. measured:

10.4 mg/L

Duration:

771

pH:

7

Temp.:

20 °C

Initial conc. measured:

10.4 mg/L

Duration:

120 h

pH:

9

Temp.:

50 °C

Initial conc. measured:

10.2 mg/L

Duration:

771 h

pH:

9

Temp.:

40 °C

Initial conc. measured:

10.3 mg/L

Duration:

771 h

pH:

9

Temp.:

20 °C

Initial conc. measured:

10.4 mg/L

Number of replicates:

Preliminary Test:
4 at each pH-value

Hydrolysis of unstable Substances (Tier 2):
16 at pH 4 at each temperature (20 and 40 °C)
18 at pH 7 at 40 °C
16 at pH 7 at 20 °C
18 at pH 9 at 40 °C
16 at pH 9 at 20 °C

Preliminary study:

A preliminary test was performed at 50±0.5 °C at three pH values: 4.0, 7.0 and 9.0. A sufficient number of measurements were made, in order to be able to estimate whether for each pH value and at 50 °C, the half-life time (t1/2) is less than 10 % of hydrolysis after 120 hours. These values correspond to a half-life time higher than one year under conditions more representative of those of the environment (25 °C).

Test performance:

The main test (Tier 2) was performed at pH 4, 7 and 9. The buffered solution of the test substance was thermostated at 20 °C and 40 °C. To test for first-order behaviour, each reaction solution was analysed in time intervals which provide at least six spaced data points normally between 10 % and 90 % hydrolysis of the substance. Individual replicate test samples (a minimum of duplicate samples contained in separate reaction vessels) were removed and the contents were analysed at each of at least six sampling times (for a minimum of twelve replicate data points). Kinetic analysis for the hydrolysis of unstable substances (Tier 2) was performed and the corresponding DT50 values was calculated. At each sampling date the pH was determined.

Transformation products:

not measured

% Recovery:

89.9

pH:

4

Temp.:

50 °C

Duration:

120 h

% Recovery:

95.5

pH:

4

Temp.:

20 °C

Duration:

771 h

% Recovery:

89.3

pH:

4

Temp.:

40 °C

Duration:

771 h

% Recovery:

89.5

pH:

7

Temp.:

50 °C

Duration:

120 h

% Recovery:

86.7

pH:

7

Temp.:

20 °C

Duration:

771 h

% Recovery:

85.1

pH:

7

Temp.:

40 °C

Duration:

771 h

% Recovery:

49.4

pH:

9

Temp.:

50 °C

Duration:

120 h

% Recovery:

72.5

pH:

9

Temp.:

20 °C

Duration:

771 h

% Recovery:

45

pH:

9

Temp.:

40 °C

Duration:

771 h

pH:

4

Temp.:

40 °C

DT50:

6 759 h

Type:

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

pH:

4

Temp.:

20 °C

DT50:

12 904 h

Type:

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

pH:

7

Temp.:

40 °C

DT50:

5 495 h

Type:

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

pH:

7

Temp.:

20 °C

DT50:

3 697 h

Type:

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

pH:

9

Temp.:

40 °C

DT50:

444 h

Type:

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

pH:

9

Temp.:

20 °C

DT50:

1 603 h

Type:

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

Details on results:

The degradation of FAT 92368/Y was more than 10 % at pH 4, 7 and 9 at 50 °C over a period of 120 hours. A Tier 2 test at 40 °C and 20 °C was performed at pH 4, 7 and 9.

Table: Degradation endpoint for hydrolysis of FAT 92368/Y

Test system Kinetic model DT50 [h]
pH 4, 40 °C SFO 6759
pH 4, 20 °C SFO 12904
pH 7, 40 °C SFO 5495
pH 7, 20 °C SFO 3697
pH 9, 40 °C SFO 444
pH 9, 20 °C SFO 1603

Table: Time course of FAT 92368/Y concentration at pH 4 at 50 °C

Time	Determined content of FAT 92368/Y in sample		Actual concentration
[h]	[mg/L]		in % of initial conc.
0	9.50	100
120	8.54	89.9

10.1 % of the test item were hydrolysed at pH 4 within 120 hours at 50 °C. A Main Test (Tier 2) was enclosed to determine the kinetic time course.

Table:  Time course of FAT 92368/Y concentration at pH 7 at 50 °C

Time	Determined content of FAT 92368/Y in sample		Actual concentration
[h]	[mg/L]		in % of initial conc.
0	10.1	100
120	9.04	89.5

10.5 % of the test item were hydrolysed at pH 7 within 120 hours at 50 °C. A Main Test (Tier 2) was enclosed to determine the kinetic time course.

 

Table: Time course of FAT 92368/Y concentration at pH 9 at 50 °C

 

Time	Determined content of FAT 92368/Y in sample		Actual concentration
[h]	[mg/L]		in % of initial conc.
0	10.2	100
120	5.04	49.4

50.6 % of the test item were hydrolysed at pH 9 within 120 hours at 50 °C. A Main Test (Tier 2) was enclosed to determine the kinetic time course.

 

Table: Time course of FAT 92368/Y concentration at pH 4 at 40 °C

Time	Conc. in 2 independent samples	Mean Conc. from 2 independent samples	Conc. in % of initial concentration	log[c(t)/c(0)]
[h]	[mg/L]	[mg/L]	[%]
0	9.976	10.1	100	0.0000
	10.14
23	9.490	9.45	93.6	-0.0287
	9.405
95	9.456	9.40	93.1	-0.0311
	9.345
195	9.244	9.29	92.0	-0.0362
	9.330
431	8.992	8.98	88.9	-0.0511
	8.963
600	9.145	9.10	90.1	-0.0453
	9.064
695	9.101	9.11	90.2	-0.0448
	9.117
771	8.976	9.02	89.3	-0.0491
	9.071

The test was stopped after 30 days. 89.3 % of the initial concentration was found after 30 days at pH 4 at 40 °C.

 

Table: Time course of FAT 92368/Y concentration at pH 4 at 20 °C

Time	Conc. in 2 independent samples	Mean Conc. from 2 independent samples	Conc. in % of initial concentration	log[c(t)/c(0)]
[h]	[mg/L]	[mg/L]	[%]
0	10.19	10.2	100	0.00000
	10.16
23	10.06	10.1	99.0	-0.00428
	10.12
95	10.07	10.0	98.0	-0.00860
	10.02
195	9.911	9.91	97.2	-0.0125
	9.914
431	9.774	9.77	95.8	-0.0187
	9.767
600	9.805	9.76	95.7	-0.0192
	9.708
695	9.775	9.76	95.7	-0.0192
	9.743
771	9.731	9.74	95.5	-0.0200
	9.757

The test was stopped after 30 days. 95.5 % of the initial concentration was found after 30 days at pH 4 at 20 °C.

 

Table: Time course of FAT 92368/Y concentration at pH 7 at 40 °C

Time	Conc. in 2 independent samples	Mean Conc. from 2 independent samples	Conc. in % of initial concentration	log[c(t)/c(0)]
[h]	[mg/L]	[mg/L]	[%]
0	10.32	10.4	100	0.0000
	10.38
23	9.269	9.27	89.1	-0.0501
	9.265
95	9.011	9.01	86.6	-0.0625
	9.017
117	9.025	9.03	86.8	-0.0615
	9.037
167	9.022	9.02	86.7	-0.0620
	9.018
195	8.911	8.91	85.7	-0.0670
	8.916
431	8.824	8.83	84.9	-0.0711
	8.841
600	8.821	8.84	85.0	-0.0706
	8.866
771	8.847	8.85	85.1	-0.0701
	8.856

The test was stopped after 30 days. 85.1 % of the initial concentration was found after 30 days at pH 7 at 40 °C.

 

Table: Time course of FAT 92368/Y concentration at pH 7 at 20 °C

Time	Conc. in 2 independent samples	Mean Conc. from 2 independent samples	Conc. in % of initial concentration	log[c(t)/c(0)]
[h]	[mg/L]	[mg/L]	[%]
0	10.39	10.4	100	0.00000
	10.44
23	10.24	10.3	99.0	-0.00420
	10.28
95	10.05	10.0	96.2	-0.0170
	10.02
195	9.648	9.68	93.1	-0.0312
	9.702
431	9.283	9.27	89.1	-0.0500
	9.261
600	9.134	9.13	87.8	-0.0566
	9.122
695	8.985	9.04	86.9	-0.0609
	9.090
771	8.997	9.02	86.7	-0.0618
	9.051

The test was stopped after 30 days. 86.7 % of the initial concentration was found after 30 days at pH 7 at 20 °C.

Table: Time course of FAT 92368/Y concentration at pH 9 at 40 °C

Time	Conc. in 2 independent samples	Mean Conc. from 2 independent samples	Conc. in % of initial concentration	log[c(t)/c(0)]
[h]	[mg/L]	[mg/L]	[%]
0	10.30	10.3	100	0.0000
	10.37
23	8.303	8.29	80.5	-0.0942
	8.285
95	5.912	5.91	57.4	-0.241
	5.915
117	5.770	5.78	56.1	-0.251
	5.780
167	5.413	5.42	52.6	-0.279
	5.433
195	5.155	5.17	50.2	-0.299
	5.180
431	4.837	4.78	46.4	-0.333
	4.730
600	4.704	4.69	45.5	-0.342
	4.670
771	4.675	4.64	45.0	-0.347
	4.613

The test was stopped after 30 days. 45.0 % of the initial concentration was found after 30 days at pH 9 at 40 °C.

 

Table: Time course of FAT 92368/Y concentration at pH 9 at 20 °C

Time	Conc. in 2 independent samples	Mean Conc. from 2 independent samples	Conc. in % of initial concentration	log[c(t)/c(0)]
[h]	[mg/L]	[mg/L]	[%]
0	10.32	10.4	100	0.00000
	10.43
23	10.28	10.3	99.0	-0.00420
	10.28
95	9.92	9.91	95.3	-0.0210
	9.90
195	9.376	9.37	90.1	-0.0453
	9.362
431	8.226	8.29	79.7	-0.0985
	8.361
600	7.942	7.93	76.3	-0.118
	7.912
695	7.745	7.72	74.2	-0.129
	7.703
771	7.562	7.54	72.5	-0.140
	7.521

The test was stopped after 30 days. 72.5 % of the initial concentration was found after 30 days at pH 9 at 20 °C.

Table: Degradation endpoint for hydrolysis of FAT 92368/Y

Test system	Kinetic model	slope a [h^-1]	Y-axis intercept b	DT50 [h]
pH 4, 40 °C	SFO	-4.14^.10^-05	-2.12^.10^-02	6759
pH 4, 20 °C	SFO	-2.30^.10^-05	-4.74^.10^-03	12904
pH 7, 40 °C	SFO	-4.66^.10^-05	-4.48^.10^-02	5495
pH 7, 20 °C	SFO	-7.95^.10^-05	-7.30^.10^-03	3697
pH 9, 40 °C	SFO	-3.27^.10^-04	-1.56^.10^-01	444
pH 9, 20 °C	SFO	-1.85^.10^-04	-4.53^.10^-03	1603

 

Validity criteria fulfilled:

yes

Conclusions:

The hydrolytic half-life at pH 7 and 20 °C was 3697 hours.

Executive summary:

The abiotic degradation of FAT 92368/Y as a function of pH in aqueous solution was determined according to OECD guideline 111 and EC method C.7 (440/2008). The degradation of FAT 92368/Y was more than 10 % at pH 4, 7 and 9 at 50 °C over a period of 120 hours. A Tier 2 test at 40 °C and 20 °C was performed at pH 4, 7 and 9. The observed degradation rates found were summarised in the following table.

 

Test system	Kinetic model	DT50 [h]
pH 4, 40 °C	SFO	6759
pH 4, 20 °C	SFO	12904
pH 7, 40 °C	SFO	5495
pH 7, 20 °C	SFO	3697
pH 9, 40 °C	SFO	444
pH 9, 20 °C	SFO	1603

Description of key information

The hydrolytic half-life at pH 7 and 20 °C was 3697 hours.

Key value for chemical safety assessment

Half-life for hydrolysis:

3 697 h

at the temperature of:

20 °C

Additional information

The abiotic degradation of FAT 92368/Y as a function of pH in aqueous solution was determined according to OECD guideline 111 and EC method C.7 (440/2008). The degradation of FAT 92368/Y was more than 10 % at pH 4, 7 and 9 at 50 °C over a period of 120 hours. A Tier 2 test at 40 °C and 20 °C was performed at pH 4, 7 and 9. The observed degradation rates found were summarised in the following table.

 

Test system	Kinetic model	DT50 [h]
pH 4, 40 °C	SFO	6759
pH 4, 20 °C	SFO	12904
pH 7, 40 °C	SFO	5495
pH 7, 20 °C	SFO	3697
pH 9, 40 °C	SFO	444
pH 9, 20 °C	SFO	1603