1-imino-1H-isoindol-3-amine

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2018-02-02 to 2018-03-29

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)

Version / remarks:

2004

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

2008

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

- Sampling intervals for the parent/transformation products:
Preliminary Test (Tier 1):
pH 4 at 50 °C: sampling at 0, 0.5, 1, 1.5, 2, 3, 3.5 and 4 h;
pH 7 at 50 °C: sampling at 0, 2, 3, 4, 4.5, 5, 5.5, 6 h;
pH 9 at 50 °C: sampling at 0, 1, 2, 2.5, 3, 3.5, 4, 4.5 h.
Main Test (Tier 2):
pH 4 at 20 °C: sampling at 0, 3, 24, 28, 48, 55, 72, 98 h;
pH 7 at 20 °C: sampling at 0, 3, 24, 48, 98, 146, 170, 191 h;
pH 9 at 20 °C: sampling at 0, 3, 24, 28, 48, 72, 98, 144 h;
pH 4 at 35 °C: sampling at 0, 1, 2, 3, 4, 5, 6, 7, 8 h;
pH 7 at 35 °C: sampling at 0, 3, 7, 24, 27, 29, 31, 47.5 h;
pH 9 at 35 °C: sampling at 0, 3, 7, 24, 28, 48, 55 h;
pH 4 at 50 °C: sampling at 0, 0.5, 1, 1.5, 2, 3, 3.5, 4 h;
pH 7 at 50 °C: sampling at 0, 2, 3, 4, 4.5, 5, 5.5, 6 h;
pH 9 at 50 °C: sampling at 0, 1, 2, 2.5, 3, 3.5, 4, 4.5 h;
- Sampling method: At each sampling time 2 mL diluent were added (dilution factor 2). The samples were homogenised by shaking after recrimbing. Two vials were prepared for each pH and each sampling date.
- Sampling intervals/times for pH measurements: same as sampling intervals for content determine
- Sample storage conditions before analysis: directly used for analysis

Buffers:

- Tested pH values: 4, 7, 9
- Type and final molarity of buffer: 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.
- Composition of buffer:
Citrate buffer pH 4 (0.05 M): Per 1 L ultra-pure water about 10.505 g citric acid monohydrate was weighed and about 60 mL of sodium hydroxide solution (1 M) was added to reach pH 4.
Phosphate buffer pH 7 (0.05 M): Per 1 L ultra-pure water about 6.805 g potassium dihydrogenphosphate was weighed and about 30 mL of sodium hydroxide solution (1 M) was added to reach pH 7.
Borate buffer pH 9 (0.05 M): Per 1 L ultra-pure water about 3.902 g boric acid and about 3.728 g potassium chloride were weighed and 21 mL of sodium hydroxide solution (1 M) were added to reach pH 9.

Details on test conditions:

TEST SYSTEM
- Type, material and volume of test flasks: 6 mL crimp vials
- Sterilisation method: Sterile buffer solutions used, sterilised by autoclaving
- Lighting: dark
- Measures taken to avoid photolytic effects: shaking in the dark
- Measures to exclude oxygen: degassing the buffers with argon for at least five minutes and purging the vessels with argon before preparing the test solution
- If no traps were used, is the test system closed/open: closed, with teflon sealed crimp caps

TEST PROCEDURE
- Test item preparation: At pH 4 and 9 about 100 mg and at pH 7 about 15 mg were given into a 100 mL volumetric flask. Afterwards the flask was brought to volume with the corresponding buffer solutions.
- Test concentration: 1000 mg/L at pH 4 and pH 9, 150 mg/L at pH 7
- Preliminary Test (Tier 1): performed at 50 ± 0.5 °C at three pH values 4, 7 and 9,
- Main Test (Tier 2): performed at pH 4, 7 and 9 at 20 °C, 35°C and 50°C

Duration:

4 h

pH:

4

Temp.:

50 °C

Initial conc. measured:

978.2 mg/L

Remarks:

Preliminary Test (Tier 1)

Duration:

6 h

pH:

7

Temp.:

50 °C

Initial conc. measured:

194.4 mg/L

Remarks:

Preliminary Test (Tier 1)

Duration:

4.5 h

pH:

9

Temp.:

50 °C

Initial conc. measured:

920.3 mg/L

Remarks:

Preliminary Test (Tier 1)

Duration:

98 h

pH:

4

Temp.:

20 °C

Initial conc. measured:

951.7 mg/L

Remarks:

Main Test (Tier 2)

Duration:

191 h

pH:

7

Temp.:

20 °C

Initial conc. measured:

102.2 mg/L

Remarks:

Main Test (Tier 2)

Duration:

144 h

pH:

9

Temp.:

20 °C

Initial conc. measured:

1 018.7 mg/L

Remarks:

Main Test (Tier 2)

Duration:

8 h

pH:

4

Temp.:

35 °C

Initial conc. measured:

1 014.8 mg/L

Remarks:

Main Test (Tier 2)

Duration:

47.5 h

pH:

7

Temp.:

35 °C

Initial conc. measured:

102.2 mg/L

Remarks:

Main Test (Tier 2)

Duration:

55 h

pH:

9

Temp.:

35 °C

Initial conc. measured:

1 018.7 mg/L

Remarks:

Main Test (Tier 2)

Duration:

4 h

pH:

4

Temp.:

50 °C

Initial conc. measured:

978.2 mg/L

Remarks:

Main Test (Tier 2)

Duration:

6 h

pH:

7

Temp.:

50 °C

Initial conc. measured:

194.4 mg/L

Remarks:

Main Test (Tier 2)

Duration:

4.5 h

pH:

9

Temp.:

50 °C

Initial conc. measured:

920.3 mg/L

Remarks:

Main Test (Tier 2)

Number of replicates:

2

Positive controls:

no

Negative controls:

no

Preliminary study:

More than 10 % of the test item were hydrolysed within 4 hours (for pH 4), respectively 6 hours (for pH 7) and 4.5 hours (for pH 9) at 50 °C. The Tier 2 test was performed for each pH value.

Transformation products:

not measured

pH:

4

Temp.:

20 °C

Hydrolysis rate constant:

-0.013 h-1

DT50:

22 h

Type:

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

Key result

pH:

7

Temp.:

20 °C

Hydrolysis rate constant:

-0.003 h-1

DT50:

94 h

Type:

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

pH:

9

Temp.:

20 °C

Hydrolysis rate constant:

-0.003 h-1

DT50:

105 h

Type:

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

pH:

4

Temp.:

35 °C

Hydrolysis rate constant:

-0.057 h-1

DT50:

5.1 h

Type:

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

pH:

7

Temp.:

35 °C

Hydrolysis rate constant:

-0.019 h-1

DT50:

18 h

Type:

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

pH:

9

Temp.:

35 °C

Hydrolysis rate constant:

-0.016 h-1

DT50:

18 h

Type:

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

pH:

4

Temp.:

50 °C

Hydrolysis rate constant:

-0.185 h-1

DT50:

1.5 h

Type:

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

pH:

7

Temp.:

50 °C

Hydrolysis rate constant:

-0.059 h-1

DT50:

5.4 h

Type:

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

pH:

9

Temp.:

50 °C

Hydrolysis rate constant:

-0.076 h-1

DT50:

4.1 h

Type:

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

Details on results:

TEST CONDITIONS
- pH, temperature maintained throughout the study: Yes

Main test Tier 2:

Time course of test item concentration at pH 4 at 20 °C:

Sampling time [h]	Concentration in 2 independent samples [mg/L]	Mean Concentration from 2 independent samples [mg/L]	Concentration in % of initial concentration [%]	log[c(t)/c(0)]	pH
0	956.0	951.7	100	0.00000	4.12
	947.4
3	841.4	841.8	88	-0.05329	4.10
	842.2
24	447.6	446.1	47	-0.32907	4.14
	444.6
28	398.0	395.9	42	-0.38091	4.14
	393.8
48	223.4	221.8	23	-0.63254	4.16
	220.2
55	177.0	176.7	19	-0.73126	4.17
	176.4
72	103.4	102.8	11	-0.96651	4.15
	102.2
98	59.2	59.5	6	-1.20398	4.17
	59.8

Time course of Test item concentration at pH 7 at 20 °C:

Sampling time [h]	Concentration in 2 independent samples [mg/L]	Mean Concentration from 2 independent samples [mg/L]	Concentration in % of initial concentration [%]	log[c(t)/c(0)]	pH
0	102.4	102.2	100	0.00000	7.10
	102.0
3	100.0	100.2	98	-0.00858	7.05
	100.4
24	87.6	87.7	86	-0.06645	7.04
	87.8
48	75.2	75.0	73	-0.13439	7.05
	74.8
98	61.4	61.3	60	-0.22199	7.05
	61.2
146	35.0	35.1	34	-0.46414	7.05
	35.2
170	26.6	26.5	26	-0.58621	7.06
	26.4
191	21.8	21.8	21	-0.67099	7.05
	21.8

Time course of Test item concentration at pH 9 at 20 °C:

Sampling time [h]	Concentration in 2 independent samples [mg/L]	Mean Concentration from 2 independent samples [mg/L]	Concentration in % of initial concentration [%]	log[c(t)/c(0)]	pH
0	1025.2	1018.7	100	0.00000	9.07
	1012.2
3	1003.6	986.8	97	-0.01382	8.97
	970.0
24	838.6	835.6	82	-0.08605	9.04
	832.6
28	815.8	817.5	80	-0.0956	9.08
	819.2
48	739.2	737.5	72	-0.1403	9.09
	735.8
72	629.4	630.5	62	-0.2084	9.09
	631.6
98	536.8	538.5	53	-0.2769	9.09
	540.2
144	396.2	395.1	39	-0.4113	9.08
	394.0

Time course of Test item concentration at pH 4 at 35 °C:

Sampling time [h]	Concentration in 2 independent samples [mg/L]	Mean Concentration from 2 independent samples [mg/L]	Concentration in % of initial concentration [%]	log[c(t)/c(0)]	pH
0	1017.0	1014.8	100	0.0000	4.10
	1012.6
1	863.2	861.9	85	-0.07092	4.07
	860.6
2	740.6	743.4	73	-0.13516	4.09
	746.2
3	662.6	660.3	65	-0.18664	4.09
	658.0
4	587.2	587.2	58	-0.23759	4.09
	587.2
5	513.4	508.7	50	-0.29992	4.09
	506.4
6	451.6	449	44	-0.35413	4.12
	449.6
7	390.6	393.4	39	-0.41155	4.12
	401.0
8	353.0	351.1	35	-0.46095	4.14
	352.4

Time course of Test item concentration at pH 7 at 35 °C:

Sampling time [h]	Concentration in 2 independent samples [mg/L]	Mean Concentration from 2 independent samples [mg/L]	Concentration in % of initial concentration [%]	log[c(t)/c(0)]	pH
0	102.4	102.2	100	0.0000	7.10
	102.0
3	95.4	95.4	93	-0.0299	7.05
	95.4
7	87.0	86.7	85	-0.0714	7.07
	86.4
24	41.8	41.7	41	-0.3893	7.03
	41.6
27	35.6	35.9	35	-0.4544	7.05
	36.2
29	33.0	32.8	32	-0.4936	7.04
	32.6
31	30.0	29.9	29	-0.5338	7.03
	29.8
47.5	13.2	13.2	13	-0.8889	7.04
	13.2

Time course of Test item concentration at pH 9 at 35 °C:

Sampling time [h]	Concentration in 2 independent samples [mg/L]	Mean Concentration from 2 independent samples [mg/L]	Concentration in % of initial concentration [%]	log[c(t)/c(0)]	pH
0	1025.2	1018.7	100	0.00000	9.07
	1012.2
3	904.8	906.0	89	-0.05092	9.02
	907.2
7	777.8	773.2	76	-0.11975	9.03
	768.6
24	409.0	409.8	40	-0.39547	9.03
	410.6
28	350.6	349.6	34	-0.4645	9.05
	348.6
48	160.8	161.9	16	-0.7988	9.02
	163.0
55	128.2	128.2	13	-0.9002	9.03
	128.2

Time course of Test item concentration at pH 4 at 50 °C:

Sampling time [h]	Concentration in 2 independent samples [mg/L]	Mean Concentration from 2 independent samples [mg/L]	Concentration in % of initial concentration [%]	log[c(t)/c(0)]	pH
0	984.6	978.2	100	0.0000	4.14
	971.8
0.5	743.6	746.6	76	-0.1173	4.10
	749.6
1	595.8	593.6	61	-0.2169	4.16
	591.4
1.5	476.2	477.6	49	-0.3114	4.13
	479.0
2	377.4	376.5	38	-0.4147	4.14
	375.6
3	261.4	261.5	27	-0.5730	4.18
	261.6
3.5	211.2	211.9	22	-0.6643	4.16
	212.6
4	172.2	172.3	18	-0.7541	4.15
	172.4

Time course of Test item concentration at pH 7 at 50 °C:

Sampling time [h]	Concentration in 2 independent samples [mg/L]	Mean Concentration from 2 independent samples [mg/L]	Concentration in % of initial concentration [%]	log[c(t)/c(0)]	pH
0	194.0	194.4	100	0.0000	7.13
	194.8
2	157.8	157.7	81	-0.0909	7.13
	157.6
3	136.4	136.4	70	-0.1539	7.13
	136.4
4	118.2	118.2	61	-0.2161	7.14
	118.2
4.5	109.4	109.4	56	-0.2497	7.14
	109.4
5	102.2	102.2	53	-0.2792	7.13
	102.2
5.5	94.0	94.1	48	-0.3151	7.13
	94.2
6	88.2	88.3	45	-0.3427	7.14
	88.4

Time course of Test item concentration at pH 9 at 50 °C:

Sampling time [h]	Concentration in 2 independent samples [mg/L]	Mean Concentration from 2 independent samples [mg/L]	Concentration in % of initial concentration [%]	log[c(t)/c(0)]	pH
0	920.2	920.3	100	0.0000	9.07
	920.4
1	800.2	799.3	87	-0.0612	8.97
	798.4
2	672.4	669.4	73	-0.1382	8.94
	666.4
2.5	610.4	610.0	66	-0.1786	8.95
	609.6
3	560.4	556.3	60	-0.2186	8.98
	552.2
3.5	515.4	515.3	56	-0.2519	8.95
	515.2
4	463.4	462.6	50	-0.2987	8.92
	461.8
4.5	416.4	419.0	46	-0.3417	8.97
	421.6

Validity criteria fulfilled:

yes

Conclusions:

The determined degradation half-life values are 22, 94, 105 h at 20°C for pH 4, 7, 9; 5.1, 18, 18 h at 35°C for pH 4, 7, 9; 1.5, 5.4, 4.1 h at 50°C for pH 4, 7, 9, respectively.

Executive summary:

The abiotic degradation of test item as a function of pH in aqueous solution was determined according to OECD guideline 111 and EC method C.7 (440/2008). 

A preliminary test was performed at 50 ± 0.5 °C at three pH values 4, 7 and 9. A sufficient number of measurements were made, in order to be able to estimate whether for each pH value and at 50 °C, less than 10 % of hydrolysis is observed after 120 hours or not. The hydrolysis of test item was more than 10 % at pH 4, 7 and 9 at 50 °C over a period of 2 hours.

The main test (Tier 2) was performed at pH 4, 7 and 9. The buffered solution of the test substance was tempered at 20 °C ± 0.5 °C, 35 °C ± 0.5 °C and 50 °C ± 0.5 °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.

The determined degradation half-life values are 22, 94, 105 h at 20°C for pH 4, 7, 9; 5.1, 18, 18 h at 35°C for pH 4, 7, 9; 1.5, 5.4, 4.1 h at 50°C for pH 4, 7, 9, respectively.

Description of key information

For this endpoint one test is available, in which theabiotic degradation of test item as a function of pH in aqueous solution was determined according to OECD guideline 111 and EC method C.7 (440/2008). 

The main test (Tier 2) was performed at pH 4, 7 and 9. The buffered solution of the test substance was tempered at 20 °C ± 0.5 °C, 35 °C ± 0.5 °C and 50 °C ± 0.5 °C. The determined degradation half-life values are 22, 94, 105 h at 20°C for pH 4, 7, 9; 5.1, 18, 18 h at 35°C for pH 4, 7, 9; 1.5, 5.4, 4.1 h at 50°C for pH 4, 7, 9, respectively.

The reported key value is the half-life at 20°C and at pH 7.

Key value for chemical safety assessment

Half-life for hydrolysis:

94 h

at the temperature of:

20 °C

Additional information

For this endpoint one test is available, in which theabiotic degradation of test item as a function of pH in aqueous solution was determined according to OECD guideline 111 and EC method C.7 (440/2008). 

A preliminary test was performed at 50 ± 0.5 °C at three pH values 4, 7 and 9. A sufficient number of measurements were made, in order to be able to estimate whether for each pH value and at 50 °C, less than 10 % of hydrolysis is observed after 120 hours or not. The hydrolysis of test item was more than 10 % at pH 4, 7 and 9 at 50 °C over a period of 2 hours.

The main test (Tier 2) was performed at pH 4, 7 and 9. The buffered solution of the test substance was tempered at 20 °C ± 0.5 °C, 35 °C ± 0.5 °C and 50 °C ± 0.5 °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.

The determined degradation half-life values are 22, 94, 105 h at 20°C for pH 4, 7, 9; 5.1, 18, 18 h at 35°C for pH 4, 7, 9; 1.5, 5.4, 4.1 h at 50°C for pH 4, 7, 9, respectively.