Benzoic acid, 2-([1,1'-biphenyl]-4-ylcarbonyl)-

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From 02 May 2019 to 07 May 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)

Version / remarks:

2004

Deviations:

yes

Remarks:

It was technically impossible to perform the study with the half-saturated solution in buffer at pH 4.0 because the test substance was highly insoluble at this pH value.

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

2008

Deviations:

yes

Remarks:

It was technically impossible to perform the study with the half-saturated solution in buffer at pH 4.0 because the test substance was highly insoluble at this pH value.

GLP compliance:

yes (incl. QA statement)

Remarks:

According to Hungarian Good Laboratory Practice Regulations of 42/2014.

Specific details on test material used for the study:

- Test substance name: 2-(4-Phenylbenzoyl)benzoic acid
- Batch/Lot number: Sarex #7650
- Analytical purity: 99.6 % (HPLC)
- Physical appearance: White powder
- Storage conditions: Controlled room temperature (15-25°C, ≤ 70 RH%), protected from light and humidity

Radiolabelling:

no

Analytical monitoring:

yes

Buffers:

- pH: 7.0 and 9.0
- Composition of buffer (pH 7.0): 73.9 mL 0.2 M Sodium hydroxide and 125 mL 0.2 M Potassium dihydrogen phosphate was diluted to 500 mL with ultrapure water
- Composition of buffer (pH 9.0): 53.5 mL 0.2 M Sodium hydroxide and 125 mL 0.2 M Boric acid and Potassium chloride was diluted to 500 mL with ultrapure water
These sterile buffer solutions were prepared using reagent grade chemicals and ultrapure, sterile water.
The pH of each buffer solution was checked with a calibrated pH meter.
The hydrolysis reaction was carried out using a dark thermostat to avoid photolytic effects. Nitrogen was bubbled into the water before the preparation of the solutions in order to exclude oxygen.

Estimation method (if used):

Estimation of test substance was performed with calibration series prepared from stock solution (~0.5 mg test substance / 1 mL acetonitrile) and working solution (10 μg/mL) with diluent. It was measured at every analytical occasions. Concentrations of the calibration samples were 0.05, 0.2, 0.5, 2, 5 and 10 μg/mL.

Details on test conditions:

TEST SYSTEM
- Test temperature: 49.5 – 50.4°C
- The hydrolysis reaction was carried out using a dark thermostat to avoid photolytic effects. Nitrogen was bubbled into the water before the preparation of the solutions in order to exclude oxygen.

TEST MEDIUM
- The buffer solutions used were sterile and prepared using reagent grade chemicals and ultrapure, sterile water.
- Preparation of test medium: 250 mL sterile solutions were prepared (~80 μg/mL of test item concentration in pH 7 buffer and ~130 μg/mL of test substance concentration in pH 9 buffer). The solutions were ultrasonicated and filtered on 0.22 μm filter. Solutions were transferred into screw cap tubes. Five from each test solution and two control tubes were prepared from each pH buffer.

OTHER TEST CONDITIONS
- The pH of each buffer solution was checked with a calibrated pH meter

PERFORMANCE OF THE TEST
250 mL sterile solutions were prepared (~80 μg/mL of test item concentration in pH 7 buffer and ~130 μg/mL of test item concentration in pH 9 buffer). The solutions were ultrasonicated and filtered on 0.22 μm filter. The pH of each buffer solution was checked with a calibrated pH meter.
Solutions were transferred into screw cap tubes. Five from each test solution and two control tubes were prepared from each pH buffer. The tubes were thermostated at 49.5 – 50.4°C.
The reaction solutions were analysed at the start of the test with three replicate samples and one control after five days with three replicate samples and one control per tubes and per pH. The 5-day samples were cooled to room temperature after 5-minutes ultrasonic water bath. Samples for the start and for the end were diluted with diluent (Acetonitrile : water = 1 : 1) 50 fold, then they were analysed with the above presented HPLC-UV method. The control samples were analysed directly, without any dilution.

Duration:

5 d

pH:

7

Initial conc. measured:

>= 66.83 - <= 68.48 other: μg/mL

Remarks:

Temp: 49.5 - 50.4 °C

Duration:

5 d

pH:

9

Initial conc. measured:

>= 119.63 - <= 121.43 other: μg/mL

Remarks:

Temp: 49.5 - 50.4 °C

Number of replicates:

Three

Positive controls:

no

Negative controls:

yes

Remarks:

two control tubes were prepared from each pH buffer

Statistical methods:

Chromatograms were evaluated using Clarity software. Calculations were carried out using Excel for Windows.

Preliminary study:

TEST CONDITIONS
- pH, sterility, temperature, and other experimental conditions maintained throughout the study: Yes

At pH7:
- Range of test substance concentrations at start (0 d): 66.83 - 68.48 μg/mL
- Range of test substance concentrations at end of the study period (5 d): 68.38 - 69.55 μg/mL
- Concentration in % of the applied amount at end of the study period (5 d): 102

At pH9:
- Range of test substance concentrations at start (0 d): 119.63 - 121.43 μg/mL
- Range of test substance concentrations at end of the study period (5 d): 121.00 - 124.25 μg/mL
- Concentration in % of the applied amount at end of the study period (5 d): 102

In the course of the preliminary test the observed hydrolysis of test substance was less than 10% after 5 days at 50 ± 0.5°C at pH 7 and 9, therefore it is considered to be hydrolytically stable under these conditions.

Transformation products:

no

% Recovery:

> 100

pH:

7.02

Temp.:

50 °C

Duration:

ca. 5 d

Remarks on result:

hydrolytically stable based on preliminary test

Remarks:

Temp. 50 ± 0.5°C

% Recovery:

> 100

pH:

9.03

Temp.:

50 °C

Duration:

ca. 5 d

Remarks on result:

hydrolytically stable based on preliminary test

Remarks:

Temp. 50 ± 0.5°C

Key result

Remarks on result:

hydrolytically stable based on preliminary test

Details on results:

Concentration of Test substance (µg/mL)
pH	Sampling time (day)	Results of the separate test vessels	Mean with the 95% confidence intervals (µg/mL)	End/Start (%)	Mean of the measured pH
7.0		Control buffer		-	7.01
	0 (Start)	66.93	67.41 ± 2.30		7.03
		66.83		-
		68.48
		Control buffer		-	7.01
	5	68.38	68.93 ± 1.46	102	7.02
		68.88
		69.55
9.0		Control buffer		-	9.00
	0 (Start)	121.43	120.36 ± 2.35		9.01
		119.63		-
		120.03
		Control buffer		-	9.01
	5	121.00	123.01 ± 4.36	102	9.03
		123.78
		124.25

Validity criteria fulfilled:

not specified

Conclusions:

Under test conditions of the preliminary study, test substance was considered to be hydrolytically stable at pH 7 and 9.

Executive summary:

A preliminary study was conducted to evaluate the hydrolysis of the test substance PBBA, according to OECD Guideline 111 (Hydrolysis as a Function of pH). Triplicates of sterile aqueous buffer solutions of test substance were incubated in the dark for 5 d at pH 7 and 9 (temp. 50 ± 0.5°C). Testing at pH 4 was not possible to conduct due to high insolubility of the test substance in the buffer solutions. Concentration of the test substance was determined at the start and at the end of incubation period using HPLC-UV method. The observed hydrolysis of test substance was less than 10% after 5 d at 50 ± 0.5°C and pH 7 and 9. Under the study conditions of the preliminary study, test substance was considered to be hydrolytically stable (Kovács, 2019).

Description of key information

The test substance was found to be hydrolytically stable at pH 7 and 9.

Additional information

A preliminary study was conducted to evaluate the hydrolysis of the test substance PBBA, according to OECD Guideline 111 (Hydrolysis as a Function of pH). Triplicates of sterile aqueous buffer solutions of test substance were incubated in the dark for 5 d at pH 7 and 9 (temp. 50 ± 0.5°C). Testing at pH 4 was not possible to conduct due to high insolubility of the test substance in the buffer solutions. Concentration of the test substance was determined at the start and at the end of incubation period using HPLC-UV method. The observed hydrolysis of test substance was less than 10% after 5 d at 50 ± 0.5°C and pH 7 and 9. Under the study conditions of the preliminary study, test substance was considered to be hydrolytically stable (Kovács, 2019).