2-benzoylbenzoic acid

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

27 Dec 2018 to 25 Jan 2019

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

March 04, 2016

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Version / remarks:

April 13, 2004

Deviations:

no

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

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Appearance: Off-white powder
Purity/Composition: 98.8%
Test item storage: At room temperature

Radiolabelling:

no

Analytical monitoring:

yes

Buffers:

Acetate buffer pH 4, 0.1 M
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
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
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.

Estimation method (if used):

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 20 mg/L using a spiking solution in DMSO. 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 50.0°C ± 0.1°C.

The spiking volume was < 1% of the sample volume. Nominal concentrations were not corrected for the spiking volume.

The concentration of the test item in the test samples was determined immediately after preparation (t=0) and after 2.4 hours and 5 days. The samples taken at t=2.4 hours and t=5 days were cooled to room temperature using running tap water.

The samples in buffer pH 4 were diluted in a 3:1 (v:v) ratio with acetonitrile and analysed. The samples in buffer pH 7 and pH 9 were diluted in a 3:1 (v:v) ratio with 1% formic acid in acetonitrile and analysed.

Blank buffer solutions containing a similar content of blank spiking solution were treated similarly as the test samples and analysed at t=0.

The pH of each of the test solutions (except for the blanks) was determined at each sampling time.

Details on test conditions:

Preparation of Solutions:
Stock Solutions:
Stock solutions of the test item were prepared in DMSO at concentrations of 2000 and 5000 mg/L.

Calibration Solutions:
Five working solutions in the concentration range of 6 – 1500 mg/L were prepared in DMSO from two stock solutions. The solutions and the stock at concentration of 5000 mg/L were 100-fold diluted with 25/75 (v/v) acetonitrile/water to obtain six calibration solutions in the concentration range of 0.06 – 50 mg/L.

Sample Injections:
Calibration solutions were injected in duplicate. Test samples were analysed by single injection.

Calibration Curves:
Calibration curves were constructed using six concentration levels. For each level, duplicate responses were used. Linear regression analysis was performed using the least squares method with a 1/concentration2 weighting factor. If necessary, one data point was excluded from the curve since the back calculated accuracy was > 15% from the nominal concentration. The coefficient of correlation I was > 0.99 for each curve.

Duration:

5 d

pH:

4

Temp.:

25 °C

Initial conc. measured:

22.9 mg/L

Duration:

5 d

pH:

7

Temp.:

25 °C

Initial conc. measured:

22.9 mg/L

Duration:

5 d

pH:

9

Temp.:

25 °C

Initial conc. measured:

22.7 mg/L

Number of replicates:

Two per pH

Positive controls:

no

Negative controls:

no

Preliminary study:

The analytical results of the preliminary test are given in Table 10 and Table 11.

At pH 4, pH 7 and pH 9, a degree of hydrolysis of < 10% was observed 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 above the criterion range of 90-110%, i.e. 114%. The slightly too high recovery did not hamper the conclusion that the test item had a half life time of more than 1 year at 25°C and was, therefore, considered not impacting the study results.

Transformation products:

not specified

% Recovery:

>= 100

pH:

4

Temp.:

25 °C

Duration:

5 d

Remarks on result:

hydrolytically stable based on preliminary test

% Recovery:

>= 100

pH:

7

Temp.:

25 °C

Duration:

5 d

Remarks on result:

hydrolytically stable based on preliminary test

% Recovery:

>= 100

pH:

9

Temp.:

25 °C

Duration:

5 d

Remarks on result:

hydrolytically stable based on preliminary test

Remarks on result:

hydrolytically stable based on preliminary test

Remarks:

At pH 4, pH 7 and pH 9, a degree of hydrolysis of < 10% was observed 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.

Table 10       

Preliminary Test:  Hydrolysis of the Test Item at pH 4, pH 7 and pH 9

pH code	Sampling time	Analyzed concentration [mg/L]	Degree of hydrolysis [%]		pH
			Individual	Mean
pH 4	0 hours	22.9			4
		22.8			4
	2.4 hours	22.9	-0.18	-0.19	4
		22.9	-0.2		4
	5 days	21.6	5.3	5.2	4.1
		21.7	5.1		4.1
pH 7	0 hours	22.9			7.1
		22.7			7.1
	2.4 hours	22.9	-0.41	-0.26	7.1
		22.9	-0.11		7.1
	5 days	21.7	5	5.1	7.1
		21.7	5.1		7.1
pH 9	0 hours	22.7			9
		22.7			9
	2.4 hours	22.9	-0.78	-0.76	9.1
		22.9	-0.74		9
	5 days	21.6	4.8	4.8	9
		21.6	4.8		9

Table 11       

Preliminary Test:  Recoveries

pH code	Nominal concentration [mg/L]	Analyzed concentration [mg/L]	Recovery [%]
			Individual	Mean
pH 4	20	22.9	114	114
	20	22.8	114
pH 7	20	22.9	115	114
	20	22.7	114
pH 9	20	22.7	114	114
	20	22.7	114

Validity criteria fulfilled:

yes

Conclusions:

The preliminary test (Tier 1) was performed for the determination of the rate of hydrolysis of 2-Benzoylbenzoic acid at pH values normally found in the environment (pH 4-9).

At each pH value a degree of hydrolysis of < 10% was observed after 5 days. According to the guideline, performance of the main study (Tier 2) was not required.

The half-life times of the test item were as follows:

pH 4: Half life > 1 year @ 25 °C
pH 7: Half life > 1 year @ 25 °C
pH 9: Half life > 1 year @ 25 °C

Executive summary:

In this guideline (OECD 111) study conducted with GLP certification, the test material (EC 201 -612 -2) was determined to have the following hydrolysis half lifes at 25 °C:

pH 4		pH 7		pH 9
Temperature [°C]	t½	Temperature [°C]	t½	Temperature [°C]	t½
25	> 1 year	25	> 1 year	25	> 1 year

Description of key information

Study conducted to recognised testing guidelines with GLP certification.

Additional information

pH 4		pH 7		pH 9
Temperature [°C]	t½	Temperature [°C]	t½	Temperature [°C]	t½
25	> 1 year	25	> 1 year	25	> 1 year