3,4-dihydroxybenzonitrile

Hydrolysis

Administrative data

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2017

Report date:

2017

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

May 31, 2008

Test guideline 2

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Version / remarks:

April 13, 2004

Test guideline 3

Qualifier:

according to guideline

Guideline:

EPA OPPTS 835.2120 (Hydrolysis of Parent and Degradates as a Function of pH at 25°C)

Version / remarks:

October 2008

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

3,4-dihydroxybenzonitrile

EC Number:

241-367-9

EC Name:

3,4-dihydroxybenzonitrile

Cas Number:

17345-61-8

Molecular formula:

C7H5NO2

IUPAC Name:

3,4-dihydroxybenzonitrile

Test material form:

solid: particulate/powder

Remarks:

white to brownish

Details on test material:

Batch 151222

Radiolabelling:

no

Study design

Analytical monitoring:

yes

Details on sampling:

- Sampling intervals for the parent/transformation products: The concentrations of the test item were determined immediately after preparation (t=0) and at several sampling points after t=0.
- Sampling method: For each sampling time, duplicate sterile vessels under vacuum were filled with 6 mL test solution and placed in the dark in a temperature controlled environment at 50.1°C 0.1°C.
- Sampling intervals/times for pH measurements: The pH of each of the test solutions (except for the blanks) was determined at each sampling time.
- Sample storage conditions before analysis: The samples not analyzed on the sampling day were stored in the freezer. Storage stability under these conditions was determined by the analysis of additional quality control (QC) samples prepared at half the nominal concentration of the test samples.

Buffers:

Acetate buffer pH 4, 0.1 M
A solution of 16.7% 0.1 M sodium acetate in water and 83.3% 0.1 M acetic acid in water. Buffer contained 0.0009% (w/v) sodium azide.
Phosphate buffer pH 7, 0.1 M
A solution of 0.1 M potassium di-hydrogen-phosphate in water adjusted to pH 7 using 10N sodium hydroxide. Buffer contained 0.0009% (w/v) sodium azide.
Borate buffer pH 9, 0.1 M
A solution of 0.1 M boric acid in water and 0.1 M potassium chloride in water adjusted to pH 9 using 10N sodium hydroxide. Buffer contained 0.0009% (w/v) sodium azide.

Details on test conditions:

The buffer solutions were filter-sterilised through a 0.2 µm FP 30/0.2 CA-S filter (Whatman, Dassel, Germany) and transferred into a sterile vessel. To exclude oxygen, nitrogen gas was purged through the solution for 5 minutes. The test item was spiked to the solutions at a target concentration of 2 mg/L using a spiking solution in acetonitrile. For each sampling time, duplicate sterile vessels under vacuum were filled with 6 mL test solution and placed in the dark in a temperature controlled environment at 50.1°C 0.1°C.
The spiking volume was < 1% of the sample volume. Nominal concentrations were not corrected for the spiking volume.

Duration of test

Duration of test 1

Duration:

5 d

pH:

4

Temp.:

50 °C

Initial conc. measured:

1.96 mg/L

Remarks:

Tier I

Duration of test 2

Duration:

5 d

pH:

7

Temp.:

50 °C

Initial conc. measured:

2.04 mg/L

Remarks:

Tier I

Duration of test 3

Duration:

5 d

pH:

9

Temp.:

20 °C

Initial conc. measured:

>= 1.98 - <= 1.99 mg/L

Remarks:

Tier I

Duration of test 4

Duration:

790 h

pH:

7

Temp.:

20 °C

Initial conc. measured:

2.13 mg/L

Remarks:

Tier II

Duration of test 5

Duration:

455 h

pH:

7

Temp.:

50 °C

Initial conc. measured:

2.12 mg/L

Remarks:

Tier II

Duration of test 6

Duration:

120 h

pH:

7

Temp.:

60 °C

Initial conc. measured:

2.12 mg/L

Remarks:

Tier II

Duration of test 7

Duration:

766 h

pH:

9

Temp.:

20 °C

Initial conc. measured:

2.18 mg/L

Remarks:

Tier II

Duration of test 8

Duration:

770 h

pH:

9

Temp.:

50 °C

Initial conc. measured:

2.18 mg/L

Remarks:

Tier II

Duration of test 9

Duration:

145 h

pH:

9

Temp.:

60 °C

Initial conc. measured:

>= 2.18 - <= 2.19 mg/L

Remarks:

Tier II

Number of replicates:

duplicate test samples

Positive controls:

no

Negative controls:

yes

Remarks:

blank buffer solutions

Results and discussion

Preliminary study:

At pH 7 and pH 9, a degree of hydrolysis of ≥ 10% was observed after 5 days. According to the guideline, the higher Tier test was required to determine the half-life time of the test item.
A degree of hydrolysis of < 10% was observed at pH 4 after 5 days. It demonstrated that the half-life time of the test item at 25°C is > 1 year. According to the guideline, no further tests were required.
No test item was detected in the blank buffer solutions.
The mean recoveries of the of the test item containing buffer solutions at t=0 fell within the criterion range of 90-110%. It demonstrated that the analytical method was adequate to support the hydrolysis study on the test item.

Test performance:

The mean recoveries of the test item containing buffer solutions at t=0 fell within the criterion range of 90-110% for both pH 7 and 9. It demonstrated that the analytical method was adequate to support the hydrolysis study on the test item.
The pH was in the range 7.0 – 7.1 and 9.0-9.1.
No test item was detected in the blank buffer solutions.

Transformation products:

not measured

Total recovery of test substance (in %)

Total recovery of test substance (in %) 1

% Recovery:

>= 95 - <= 100

pH:

7

Temp.:

20 °C

Duration:

>= 0 - <= 790 h

Total recovery of test substance (in %) 2

% Recovery:

>= 2.4 - <= 100

pH:

7

Temp.:

50 °C

Duration:

>= 0 - <= 455 h

Total recovery of test substance (in %) 3

% Recovery:

>= 3.2 - <= 100

pH:

7

Temp.:

60 °C

Duration:

>= 0 - <= 120 h

Total recovery of test substance (in %) 4

% Recovery:

>= 95 - <= 100

pH:

9

Temp.:

20 °C

Duration:

>= 0 - <= 766 h

Total recovery of test substance (in %) 5

% Recovery:

>= 3.9 - <= 100

pH:

9

Temp.:

50 °C

Duration:

>= 0 - <= 770 h

Total recovery of test substance (in %) 6

% Recovery:

>= 7.8 - <= 100

pH:

9

Temp.:

60 °C

Duration:

>= 0 - <= 145 h

Dissipation DT50 of parent compound

Dissipation DT50 of parent compound 1

pH:

7

Temp.:

20 °C

Hydrolysis rate constant:

0 h-1

DT50:

283 d

Type:

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

Dissipation DT50 of parent compound 2

pH:

7

Temp.:

25 °C

Hydrolysis rate constant:

0 h-1

DT50:

128 d

Type:

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

Dissipation DT50 of parent compound 3

pH:

7

Temp.:

50 °C

Hydrolysis rate constant:

0.008 h-1

DT50:

3.5 d

Type:

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

Dissipation DT50 of parent compound 4

pH:

7

Temp.:

60 °C

Hydrolysis rate constant:

0.029 h-1

DT50:

1 d

Type:

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

Dissipation DT50 of parent compound 5

pH:

9

Temp.:

20 °C

Hydrolysis rate constant:

0 h-1

DT50:

269 d

Type:

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

Dissipation DT50 of parent compound 6

pH:

9

Temp.:

25 °C

Hydrolysis rate constant:

0 h-1

DT50:

139 d

Type:

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

Dissipation DT50 of parent compound 7

pH:

9

Temp.:

50 °C

Hydrolysis rate constant:

0.004 h-1

DT50:

6.8 d

Type:

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

Dissipation DT50 of parent compound 8

pH:

9

Temp.:

60 °C

Hydrolysis rate constant:

0.017 h-1

DT50:

1.7 d

Type:

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

Details on results:

TEST CONDITIONS
- pH, sterility, temperature, and other experimental conditions maintained throughout the study: Yes
- Anomalies or problems encountered (if yes): /

Any other information on results incl. tables

pH 7:

Table 16        
Main Test pH 7: Statistical Parameters Regression Curves

Temperature (°C)	Slope [hours^-1]	Intercept	Coefficient of correlation
20	-4.42´10^-5	1.99	0.574
50	-3.62´10^-3	2.08	0.997
60	-1.24´10^-2	2.11	0.98

pH 9:

Table 21        
Main Test pH 9: Recoveries

Temperature (°C)	Nominal concentration [mg/L]	Analyzed concentration [mg/L]	Recovery [%]
			Individual	Mean
20	2.00	2.18	109	109
	2.00	2.18	109
50	2.00	2.18	109	109
	2.00	2.18	109
60	2.00	2.19	109	109
	2.00	2.18	109

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Executive summary:

The preliminary test (Tier 1) and main study (Tier 2) were performed for the determination of the rate of hydrolysis of CH02906 at pH values normally found in the environment (pH 4-9).

Hydrolysis of the test item followed first-order reaction rates and the associated half-life times were as follows:

pH 4		pH 7		pH 9
Temperature [°C]	t½	Temperature [°C]	t½	Temperature [°C]	t½
		20	283 days	20	269 days
25	> 1 year	25	128 days	25	139 days
		50	3.5 days	50	6.9 days
		60	1.0 days	60	1.7 days