3-anilino-5-methyl-5-(4-phenoxyphenyl)-1,3-oxazolidine-2,4-dione;famoxadone (ISO)

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: European Union Commission Directive 94/37 EC amending Council Directive 91/414/EEC. Physical and Chemical Properties of the Active Substance. Point 2.9.1 Hydrolysis

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: USA: 40 CFR 158.290. Environmental Fate Data Requirements. Degradation Studies-lab. Hydrolysis

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

Substance name: [14C-Phenoxyphenyl]DPX-JE874
Lot #: 2675-268
Specific activity: 64.61 µCi/mg
Radiochemical purity: >96%

Substance name: [14C-Phenylamino]DPX-JE874
Lot #: 2868-107; 3048-238
Specific activity: 52.51 µCi/mg; 58.53 µCi/mg
Radiochemical purity: 95%; 98.7%

Substance name: IN-JE874
Lot #: IN-JE874-92
Purity: 99.6%

Radiolabelling:

yes

Analytical monitoring:

yes

Details on sampling:

- Sampling intervals for the parent/transformation products: In the experiments designed to determine the rate of degradation of test substance in solution, sampling intervals were pH dependent.
[14C-Phenoxyphenyl] Radiolabel: pH 5: 0, 2, 6, 10, 16, 30 days; pH 7: 0, 0.25, 0.5, 1.0, 1.5, 2.0, 5.0 days; pH 9: 0, 0.75, 1.5, 2.25, 3.0, 4.0, 5.0 hours. [14C-Phenylamino] Radiolabel: pH 5: 0, 2, 7, 16, 21, 30 days; pH 7: 0, 0.25, 0.5, 1.0, 1.5, 2.0, 5.0 days; pH 9: 0, 0.75, 1.5, 2.25, 3.0, 4.0, 5.0 hours.
In the experiments designed to identify the degradation products, non-volatile degradation products were characterized and identified after 2 days incubation (pH 9). Volatile degradation products were collected after 3 days of incubation at pH 9.
In the experiments designed to determine material balance for the [14C-PA] label, samples (including traps) were taken after 3 days of incubation at pH 9, 25°C, and after 3 days of incubation at pH 7, 35°C.
- Sample storage conditions before analysis: Frozen (<-15°C)

Buffers:

pH 5: A total of 148 mL of 0.02 M acetic add plus 352 mL of 0.02 M sodium acetate was transferred to a 1000 mL volumetric flask and diluted with deionized water to produce a 0.01 M pH 5.0 acetate buffer solution.

pH 7: A total of 195 mL of 0.02 M sodium phosphate (monobasic) plus 305 mL of 0.02 M sodium phosphate (dibasic) was transferred to a 1000-mL volumetric flask and diluted with deionized water to produce a 0.01 M pH 7.0 phosphate buffer solution.

pH 9: A 0.2 M glycine solution was prepared by transferring 1.5 g of glycine (75.07 g/mole) to a 100-mL volumetric flask and diluting it to volume with deionized water. A 0.2 M sodium hydroxide solution was prepared by transferring 1.6 g of 50% NaOH to a 100-mL volumetric flask and diluting to volume with deionized water. Twenty-five mL of the 0.2 M glycine solution and 4.4 mL of the 0.2 M NaOH solution were diluting it to volume with deionized water. A 0.2 M sodium hydroxide solution was prepared by transferring 1.6 g of 50% NaOH to a 100-mL volumetric flask and diluting to volume with deionized water. Twenty-five mL of the 0.2 M glycine solution and 4.4 mL of the 0.2 M NaOH solution were transferred to a 100-mL volumetric flask and diluted to volume with deionized water. One hundred mL of this 0.05 M glycine buffer were transferred to a 500-mL volumetric flask and diluted to volume with deionized water. The pH of this 0.01 M glycine buffer was 9.0.

Details on test conditions:

TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: For kinetic experiments: The test vessels for both [14C-POP] and [14C-PA] radiolabels were 20-mL borosilicate scintillation vials equipped with polyethylene-lined screw caps. For material balance experiments: The test vessel was a sterilized, large, circular borosilicate glass container which held at least 250 mL of solution.
- Sterilisation method: All glassware and test vessels were sterilized by autoclaving for 20 minutes at -120°C immediately prior to use. The buffers were filtered through 0.22-µm sterile, disposable filtration
units into autoclaved culture bottles. The stock solutions of [14C]test substance were prepared in acetonitrile. Samples were taken for microbiological examination for buffer solutions from the kinetics of degradation experiments at pH 5 and 7 after 30 days.
- Lighting: Dark
- Measures taken to avoid photolytic effects: With exception of vessels taken for immediate analysis, vessels containing treated buffer solutions were placed in a temperature-controlled incubator at 25 ± 2°C in the dark.
- Details of traps for volatile, if any: For kinetic experiments, there was no provision for trapping of volatiles. For material balance experiments, specialized glassware was used to trap organic volatiles for GC and mass spectral analysis. The test system was a flat-bottomed, borosilicate glass container (approximate volume 4 L) with a single opening. The opening was dosed using an all glass assembly with an inlet tube and an outlet tube.

Duration:

30 d

pH:

5

Temp.:

25 °C

Initial conc. measured:

25 µg/L

Duration:

30 d

pH:

7

Temp.:

25 °C

Initial conc. measured:

25 µg/L

Duration:

30 d

pH:

9

Temp.:

25 °C

Initial conc. measured:

25 µg/L

Positive controls:

no

Negative controls:

no

Preliminary study:

The test substance was found to be highly insoluble in water. Preliminary experiments indicated that the test substance adhered to glass. Accurate quantitation of test substance and its hydrolysis products in aqueous solutions was limited by these physical characteristics.

Transformation products:

yes

Remarks:

IN-MN968, IN-JL856, IN-JS940, IN-Н3310, phenol, catechol, and benzene.

No.:

#7

No.:

#6

No.:

#5

No.:

#4

No.:

#3

No.:

#2

No.:

#1

% Recovery:

97.4

pH:

7

Temp.:

35 °C

Duration:

3 d

Remarks on result:

other: Material balance experiment

% Recovery:

97.6

pH:

9

Temp.:

25 °C

Duration:

3 d

Remarks on result:

other: Material balance experiment

% Recovery:

93

pH:

5

Temp.:

25 °C

Duration:

30 d

Remarks on result:

other: [14C-Phenylamino] Radiolabel (Kinetic experiment)

% Recovery:

80

pH:

7

Temp.:

25 °C

Duration:

5 d

Remarks on result:

other: [14C-Phenylamino] Radiolabel (Kinetic experiment)

% Recovery:

91

pH:

9

Temp.:

25 °C

Duration:

5 h

Remarks on result:

other: [14C-Phenylamino] Radiolabel (Kinetic experiment)

% Recovery:

97

pH:

5

Temp.:

25 °C

Duration:

30 d

Remarks on result:

other: [14C-Phenoxyphenyl] Radiolabel (Kinetic experiment)

% Recovery:

92

pH:

7

Temp.:

25 °C

Duration:

5 d

Remarks on result:

other: [14C-Phenoxyphenyl] Radiolabel (Kinetic experiment)

% Recovery:

94

pH:

9

Temp.:

25 °C

Duration:

5 h

Remarks on result:

other: [14C-Phenoxyphenyl] Radiolabel (Kinetic experiment)

Key result

pH:

5

Temp.:

25 °C

Hydrolysis rate constant:

0.017 d-1

DT50:

41 d

Key result

pH:

7

Temp.:

25 °C

Hydrolysis rate constant:

0.341 d-1

DT50:

2 d

Key result

pH:

9

Temp.:

25 °C

Hydrolysis rate constant:

10.7 d-1

DT50:

0.065 d

Validity criteria fulfilled:

yes

Conclusions:

Hydrolysis plays a major role in the degradation of the test substance. Because of the hydrolytic instability of the test substance and most of its major degradation products, they should not persist in most aquatic environments.

Executive summary:

The hydrolysis of the test substance has been studied in aqueous solutions at pH 5, 7, and 9. The study was conducted using test substance labeled separately with carbon-14 in the phenoxyphenyl ring and in the phenylamino ring. The rate of application was a nominal 25 µg/L. Test solutions were incubated under sterile conditions for up to 30 days in darkness at 25 ± 2°C.

At pH 9, the test substance was rapidly degraded with a half-life of 1.55 hours (0.0646 day). At pH 7, the half-life was 2 days, and at pH 5, the half-life was 41 days. The degradation rate was inversely proportional to the hydrogen ion [H+] concentration.

Several products were identified from the hydrolysis solutions using GC/MS, radio-GC and/or LC/MS. Identified products included IN-MN968, IN-JL856, IN-JS940, IN-H3310, phenol, catechol, and benzene. Polar, organic acid(s) were characterized, based on HPLC retention times and partitioning characteristics.

Two hydrolytic degradation pathways were observed. The quantitatively more important route involved hydrolysis of the amide linkage to give IN-MN968 (1-carboxy-1-(4-phenoxyphenyl)ethyl 2-phenylhydrazinecarboxylate monosodium salt). IN-MN968 underwent rapid hydrolysis (half-life at 25°C, pH 7 = 7 hours) to yield IN-JS940 (α-hydroxy-α-methyl-4-phenoxybenzeneacetic acid) and a proposed intermediate, the free acid of IN-KТ983. IN-KT983 (potassium 2-phenylhydrazinecarboxylate) is a very unstable compound which degrades in low concentration solutions to phenol, catechol, polar, organic add(s), and benzene probably via a radical mechanism.

Hydrolysis of the carbamate ester group (followed by decarboxylation) gave IN-JL856 (α-hydroxy-α-methyl-4-phenoxybenzeneacetic acid-2-phenylhydrazide). This was a relatively minor degradation pathway; less than 20% of the applied test substance degraded by this route. IN-JL856 was shown to degrade slowly at 25°C (at pHs 5,7, and 9).

A third degradation pathway from test substance was also observed in dilute solution. This degradation pathway involved the formation of IN-H3310 [1-(4-phenoxyphenyl)ethanone] which was only ~11% of the [14C-phenoxyphenyl] label at pH 7 (phosphate buffer). The mechanism of formation of IN-H3310 probably involves reaction with oxygen.

Degradation rate data were obtained for IN-MN968, IN-JL856, IN-JS940, and IN-H3310. The latter two compounds were hydrolytically stable.

Hydrolysis plays a major role in the degradation of test substance. Because of the hydrolytic instability of the test substance and most of its major degradation products, they should not persist in most aquatic environments.

Description of key information

Study Type	Study Details	Value	Guideline	Reliability
Hydrolysis	Tested at pH 5, pH 7 and pH 9	DT50 =41 days at pH 5; DT50 =2 days at pH 7; DT50 = 0.065 days at pH 9	EPA 161 -11	1

 

Key value for chemical safety assessment

Half-life for hydrolysis:

2 d

at the temperature of:

25 °C