4'-Ethyl-3-fluorbiphenyl-4-boronic acid

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

November 16, 2018 - May 20, 2019

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)

Version / remarks:

European Commission Regulation (EC) No. 440/2008

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

- Sampling intervals for the parent/transformation products:
- Sampling method: A stock solution of the test item was prepared by dissolving the test item in acetonitrile using the ultrasonic bath for 15 min. 0.5 ml of the stock solution were taken and filled up to 50 ml with buffer at pH 4 or with a buffer at pH 9, respectively.
- Sampling intervals/times for pH measurements: The pH values of the test item solutions were measured at the end of the experiments.

Buffers:

- pH: 4, 7, and 9
- Composition of buffer:

pH 4: 21.01 g citric acid monohydrate was dissolved in 200 ml sodium hydroxide solution. This solution was filled up to a volume of 1000 ml with demineralized water. 44 ml of hydrochloric acid was added to 560 ml of this solution and filled up to a volume of 1000 ml with demineralized water. The pH value was adjusted to pH 4 for each hydrolysis temperature.

pH 7: 13.61 g potassium dihydrogen phosphate was dissolved in 1000 ml demineralized water. 30 ml of sodium hydroxide solution was added to 500 ml of this solution and filled up to a volume of 1000 ml with demineralized 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 was dissolved in 1000 ml demineralized water. 21 ml of sodium hydroxide solution was added to 500 ml of this solution and filled up to a volume of 1000 ml with demineralized water. The pH value was adjusted to pH 9 for each hydrolysis temperature.

Details on test conditions:

TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: glass flask
- Measures to exclude oxygen: Flasks were baked out at 110°C and flooded with nitrogen. Before adding the test item into the buffer solution the later were flooded with nitrogen for minutes.

Duration:

720 h

pH:

4.1

Temp.:

50 °C

Initial conc. measured:

3.93 mg/L

Duration:

720 h

pH:

4.1

Temp.:

50 °C

Initial conc. measured:

3.92 mg/L

Duration:

381 h

pH:

9.2

Temp.:

50 °C

Initial conc. measured:

3.91 mg/L

Duration:

621 h

pH:

9.2

Temp.:

50 °C

Initial conc. measured:

4.01 mg/L

Duration:

742 h

pH:

4.1

Temp.:

40 °C

Initial conc. measured:

3.56 mg/L

Duration:

742 h

pH:

4.1

Temp.:

40 °C

Initial conc. measured:

3.7 mg/L

Duration:

742 h

pH:

9.2

Temp.:

40 °C

Initial conc. measured:

3.81 mg/L

Duration:

742 h

pH:

9.2

Temp.:

40 °C

Initial conc. measured:

3.86 mg/L

Duration:

720 h

pH:

9

Temp.:

25 °C

Initial conc. measured:

3.65 mg/L

Duration:

720 h

pH:

9

Temp.:

25 °C

Initial conc. measured:

3.74 mg/L

Duration:

261 h

pH:

4

Temp.:

60 °C

Initial conc. measured:

3.45 mg/L

Duration:

261 h

pH:

4

Temp.:

60 °C

Initial conc. measured:

3.43 mg/L

Number of replicates:

Two

Positive controls:

no

Negative controls:

no

Preliminary study:

For the experiments of the preliminary test (tier 1) 0.5 ml of the stock solution were taken and filled up to 50 ml with the relevant buffers. For the solutions using buffer at pH 4 and pH 9 clear solutions resulted. Adding the stock solution to the buffer solution at pH 7 precipitation was observed. Therefore, instead of 1 % acetonitrile as solubilizer, methanol and THF were tried. But again, precipitation was observed after adding the buffer solution at pH 7. Therefore, the study of the hydrolysis was only performed at pH 4 and pH 9. For each pH value duplicate preliminary hydrolysis tests (tier 1) were performed.
At pH 4 and pH 9 more than 10 % of the test item hydrolysed within 5 days, therefore additional testing (tier 2) was necessary.

Test performance:

All recoveries of the standards indicated a sufficient accuracy of the analytical method.

Transformation products:

no

Key result

pH:

4.1

Temp.:

50 °C

Hydrolysis rate constant:

0.003 h-1

DT50:

229 h

Type:

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

Remarks on result:

other: experiment 5

Key result

pH:

4.1

Temp.:

50 °C

Hydrolysis rate constant:

0.003 h-1

DT50:

234 h

Type:

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

Remarks on result:

other: experiment 6

Key result

pH:

4.1

Temp.:

40 °C

Hydrolysis rate constant:

0.001 h-1

DT50:

740 h

Type:

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

Remarks on result:

other: experiment 9

Key result

pH:

4.1

Temp.:

40 °C

Hydrolysis rate constant:

0.001 h-1

DT50:

730 h

Type:

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

Remarks on result:

other: experiment 10

Key result

pH:

4

Temp.:

60 °C

Hydrolysis rate constant:

0.008 h-1

DT50:

88 h

Type:

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

Remarks on result:

other: experiment 17

Key result

pH:

4

Temp.:

60 °C

Hydrolysis rate constant:

0.008 h-1

DT50:

87 h

Type:

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

Remarks on result:

other: experiment 18

Key result

pH:

9.2

Temp.:

50 °C

Hydrolysis rate constant:

0.005 h-1

DT50:

127 h

Type:

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

Remarks on result:

other: experiment 7

Key result

pH:

9.2

Temp.:

50 °C

Hydrolysis rate constant:

0.004 h-1

DT50:

127 h

Type:

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

Remarks on result:

other: experiment 8

Key result

pH:

9.2

Temp.:

40 °C

Hydrolysis rate constant:

0.001 h-1

DT50:

619 h

Type:

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

Remarks on result:

other: experiment 11

Key result

pH:

9.2

Temp.:

40 °C

Hydrolysis rate constant:

0.002 h-1

DT50:

465 h

Type:

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

Remarks on result:

other: experiment 12

Key result

pH:

9

Temp.:

25 °C

Hydrolysis rate constant:

0 h-1

DT50:

1 897 h

Type:

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

Remarks on result:

other: experiment 15

Key result

pH:

9

Temp.:

25 °C

Hydrolysis rate constant:

0.001 h-1

DT50:

689 h

Type:

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

Remarks on result:

other: experiment 16

Other kinetic parameters:

The experiments at pH 4 showed a linear relationship between In k(obs) and 1/T. Therefore, an extrapolation of the half-life time was possible: The test item had a half-life of 4305 hours (179 days) at pH 4 and a temperature of 25 °C.
The experiments for tier 2 at pH 9 showed a deviation in the double determinations of the k(obs) values for 50, 25 and 40 °C. However, a linear relationship between In k(obs) and 1/T could be observed. Using the regression shown above, the test item had a half-life of 1287 hours (54 days) at pH 9 and a temperature of 25 °C

Results of preliminary test

pH of buffer solution	pH of test item solution^a	Duration (d)	C0^b(mg/L)	Ct^c(mg/L)	Ct/C0	Decomposition (%)
4	4.2	5	3.37	2.51	0.744	26
4	4.2	5	3.42	2.49	0.728	27
9	9.3	5	3.67	2.33	0.634	37
9	9.3	5	3.89	1.53	0.395	61

Amount of hydrolysis products at pH 4

	Component	Peak area in mAU*s	Amount of hydrolysis products in %
Experiment 5 (50 °C)	Test item (t = c0)	198.2	-
	Peak at 4.7 min (t = 720 h)	6.6	3.3
	Peak at 6.5 min (t = 720 h)	3.7	1.9
Experiment 9 (40 °C)	No hydrolysis products detected
Experiment 17 (60 °C)	Test item (t = c0)	182.2	-
	Peak at 6.3 min (t = 261 h)	9.8	5.4

 

Amount of hydrolysis products at pH 9

	Component	Peak area in mAU*s	Amount of hydrolysis products in %
Experiment 7 (50 °C)	Test item (t = c0)	197.1	-
	Peak at 4.4 min (t = 381 h)	10.8	5.5
	Peak at 6.2 min (t = 381 h)	9.1	4.6
Experiment 11 (40 °C)	Test item (t = c0)	201.4	-
	Peak at 4.7 min (t = 742 h)	2.4	1.2
	Peak at 6.5 min (t = 742 h)	2.1	1.0
Experiment 15 (25 °C)	Test item (t = c0)	193.0	-
	Peak at 4.6 min (t = 720 h)	2.4	1.2
	Peak at 6.4 min (t = 720 h)	1.3	0.7
	Peak at 7.1 min (t = 720 h)	6.4	3.3

 

No major hydrolysis products (>= of the applied dose) were identified in the experiments. Therefore, the identification of major hydrolysis products was not necessary.

Validity criteria fulfilled:

yes

Conclusions:

No major hydrolysis products (>= 10% of the applied dose) were identified in the experiments. Therefore, the identification of major hydrolysis products was not necessary.

Executive summary:

A hydrolysis study was performed according to EU Method C.7 under GLP conditions. The pretests are done at 50 ± 0.5 °C with buffers at pH 4, 7 and 9. At pH 4 and pH 9 more than 10 % of the test item hydrolysed within 5 days, therefore additional testing (tier 2) was necessary. The tier 2 tests are done at three different temperatures in the range of 10 °C to 70 °C with buffers at pH 4, 7 and 9.

At least 6 aliquots are taken between a decomposition rate of 10 and 90 %. The tests are conducted until 90 % hydrolysis of the test item is observed or for 30 days whichever occurs first. For each pH value duplicate hydrolysis tests (tier 2) are performed. No hydrolysis product could be detected in tier 1. In tier 2 a different analytical method was used, and some smaller peaks arose during the hydrolysis test in the HPLC chromatograms. The amount of these hydrolysis products was evaluated. For this purpose, the peak areas of the hydrolysis products at the end of the experiments were compared with the peak area of the test item at the beginning of the experiments (in each case one of the double experiments at pH 4 and pH 9 was evaluated).

No major hydrolysis products (~ 10 % of the applied dose) were identified in the experiments of tier 2. Therefore, the identification of major hydrolysis products was not necessary.

Description of key information

Calculated half-value times were as followed:

pH 4: 339 d at 20°C and 179 d at 25°C

pH 9: 82 d at 20°C and 54 d at 25°C.

Key value for chemical safety assessment

Half-life for hydrolysis:

54 d

at the temperature of:

25 °C

Additional information

No major hydrolysis products (>= 10 % of the applied dose) were identified in the experiments of tier 2. Therefore, the identification of major hydrolysis products was not necessary.