Chromate(2-), [2,4-dihydro-4-[(2-hydroxy-4-nitrophenyl)azo]-5-methyl-2-phenyl-3H-pyrazol-3-onato(2-)][3-[(4,5-dihydro-3-methyl-5-oxo-1-phenyl-1H-pyrazol-4-yl)azo]-2-hydroxy-5-nitrobenzenesulfonato(3-)]-, disodium

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

15 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 + 0.1 % 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 10.4 mg/L at pH 4, 10.4 mg/L at pH 7 and 10.1 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 distilled or 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 was 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. 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:

10.4 mg/L

Duration:

720 h

pH:

4

Temp.:

40 °C

Initial conc. measured:

10.3 mg/L

Duration:

720 h

pH:

4

Temp.:

20 °C

Initial conc. measured:

10.2 mg/L

Duration:

120 h

pH:

7

Temp.:

50 °C

Initial conc. measured:

10.4 mg/L

Duration:

120 h

pH:

9

Temp.:

50 °C

Initial conc. measured:

10.1 mg/L

Number of replicates:

Preliminary Test:
4 at each pH-value

Hydrolysis of unstable Substances (Tier 2):
18 at each temperature (20 and 40 °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. 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:

61.8

pH:

4

Temp.:

50 °C

Duration:

120 h

% Recovery:

93.6

pH:

4

Temp.:

20 °C

Duration:

720 h

% Recovery:

34.1

pH:

4

Temp.:

40 °C

Duration:

720 h

% Recovery:

97.1

pH:

7

Temp.:

50 °C

Duration:

120 h

% Recovery:

96.7

pH:

9

Temp.:

50 °C

Duration:

120 h

pH:

4

Temp.:

20 °C

DT50:

6 502 h

Type:

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

pH:

4

Temp.:

40 °C

DT50:

449 h

Type:

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

Key result

pH:

7

Temp.:

25 °C

DT50:

> 1 yr

Type:

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

pH:

9

Temp.:

25 °C

DT50:

> 1 yr

Type:

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

Details on results:

It was shown that the hydrolysis of FAT 20060/F is negligible at pH 7 and pH 9. The half-life times at pH 7 and 9 are expected to be above one year at 25 °C in each case. Because the test item is stable to hydrolysis at pH 7 and pH 9 no further hydrolysis tests were necessary. The degradation of FAT 20060/F was more than 10 % at pH 4 at 50 °C over a period of 120 hours. A Tier 2 test at 40 °C and 20 °C was performed at pH 4.

DT50 value as persistence endpoint is shown below:
Test system Kinetic model DT50
[h]
pH 4, 40 °C SFO 449
pH 4, 20 °C SFO 6502

Table 1: Time course of FAT 20060/F concentration at pH 4 at 50 °C

Time	Determined Content of FAT 20060/F in Sample		Actual concentration
[h]	[mg/L]		in % of initial conc.
0	10.4	100
120	6.43	61.8

38.2 % 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 2: Time course of FAT 20060/F concentration at pH 7 at 50 °C

 

Time	Determined Content of FAT 20060/F in Sample		Actual concentration
[h]	[mg/L]		in % of initial conc.
0	10.4	100
120	10.1	97.1

No significant changes of the content in the samples were observed. At pH 7 less than 10 % of the test item were hydrolysed within 120 hours at 50°C.

 

Table 3: Time course of FAT 20060/F concentration at pH 9 at 50 °C

 

Time	Determined Content of FAT 20060/F in Sample		Actual concentration
[h]	[mg/L]		in % of initial conc.
0	10.1	100
120	9.77	96.7

No significant changes of the content in the samples were observed. At pH 9 less than 10 % of the test item were hydrolysed within 120 hours at 50 °C.

 

Table 4: Time course of FAT 20060/F 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	10.3	10.3	100	0.00000
	10.2
46	9.66	9.62	93.4	-0.02966
	9.58
119	8.52	8.51	82.6	-0.08291
	8.50
214	7.28	7.33	71.2	-0.14773
	7.38
336	5.98	5.94	57.7	-0.23905
	5.90
456	4.90	4.99	48.4	-0.31474
	5.08
524	4.56	4.50	43.7	-0.35962
	4.44
624	3.92	4.00	38.8	-0.41078
	4.08
720	3.48	3.51	34.1	-0.46753
	3.54

The test was stopped after 30 days. 34.1 % of the initial concentration was found after 30 days at pH 4 at 40 °C.

 

Table 5: Time course of FAT 20060/F 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	10.2	10.2	100	0.00000
	10.1
46	10.2	10.2	100	0.00000
	10.1
119	10.2	10.2	100	0.00000
	10.1
214	9.80	9.89	97.0	-0.01340
	9.98
336	9.82	9.82	96.3	-0.01649
	9.82
456	9.78	9.78	95.9	-0.01826
	9.78
524	9.50	9.60	94.1	-0.02633
	9.70
624	9.56	9.51	93.2	-0.03042
	9.46
720	9.58	9.55	93.6	-0.02860
	9.52

The test was stopped after 30 days. 93.6 % of the initial concentration was found after 30 days at pH 4 at 20 °C.

Validity criteria fulfilled:

yes

Conclusions:

FAT 20060/F is stable to hydrolysis at pH 7 and pH 9.

Executive summary:

It was shown that the hydrolysis of FAT 20060/F is negligible at pH 7 and pH 9. The half-life times at pH 7 and 9 are expected to be above one year at 25 °C in each case. Because the test item is stable to hydrolysis at pH 7 and pH 9 no further hydrolysis tests were necessary. The degradation of FAT 20060/F was more than 10 % at pH 4 at 50 °C over a period of 120 hours. A Tier 2 test at 40 °C and 20 °C was performed at pH 4. 

DT50 value as persistence endpoint is shown below:

Test system Kinetic model DT50

[h]

pH 4, 40 °C SFO 449

pH 4, 20 °C SFO 6502

Description of key information

FAT 20060/F is stable to hydrolysis at pH 7 and 9.

Key value for chemical safety assessment

Half-life for hydrolysis:

1 yr

at the temperature of:

25 °C

Additional information

It was shown that the hydrolysis of FAT 20060/F is negligible at pH 7 and pH 9. The half-life times at pH 7 and 9 are expected to be above one year at 25 °C in each case. Because the test item is stable to hydrolysis at pH 7 and pH 9 no further hydrolysis tests were necessary. The degradation of FAT 20060/F was more than 10 % at pH 4 at 50 °C over a period of 120 hours. A Tier 2 test at 40 °C and 20 °C was performed at pH 4.

DT50 value as persistence endpoint is shown below:

Test system Kinetic model DT50

[h]

pH 4, 40 °C SFO 449

pH 4, 20 °C SFO 6502