ethyl 5,5-diphenyl-2-isoxazoline-3-carboxylate

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:

EPA Guideline Subdivision N 161-1 (Hydrolysis)

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

GLP compliance:

yes

Radiolabelling:

yes

Analytical monitoring:

yes

Details on sampling:

- Sampling intervals for the parent/transformation products: depending on pH treatment: 3 hours, 6 hours, day 1, 3, 5, 7, 14, 15, 21, 28, 29, 30
- Sampling method: At each timepoint, duplicate samples were removed from the constant temperature environment and analyzed.
- Sampling intervals/times for pH measurements: The pH of the hydrolysis samples was monitored at the start and termination of each series. In all cases, pH did not significantly change during the course of the study
- Sample storage conditions before analysis: All samples were analyzed by HPLC within 5 minutes of removal from the constant temperature environment and so storage stability was not an issue.
- Other observation, if any: a single Day 0 replicate of the pH 5 at 25 °C hydrolysis set was anomalously low

Buffers:

- pH: 4, 5, 6, 7, 9
- Type of buffer: pH 4 Buffer Solution: 0.025 M Acetate; pH 5 Buffer Solution: 0.025 M Acetate; pH 6 Buffer Solution: 0.025 M Acetate; pH 7 Buffer Solution: 0.025 M Phosphate; pH 9 Buffer Solution: 0.024 M Borate
- Composition of buffer: pH 4 Buffer Solution: Sodium acetate trihydrate (3.4 g) was dissolved in water to 1 L total volume and labeled as Solution A. Glacial acetic acid (0.71 mL at density of 1.05) was diluted to 500 mL and labeled Solution B. The combination of 53 mL of solution A and 150 mL of Solution B resulted in 203 ml of 0.025 M acetate solution buffered to pH 3.99 (as determined by pH meter); pH 5 Buffer Solution: 0.025 M Acetate: The combination of 330 mL of Solution A and 105.8 mL of Solution B resulted in 435 mL of 0.025 M acetate solution buffered to pH 4.99 (as determined by pH meter).; pH 6 Buffer Solution: 0.025 M Acetate: The combination of 200 mL of Solution A and 7.7 mL of Solution B resulted in 208 mL of 0.025 M acetate solution buffered to pH 6.03 (as determined by pH meter).; pH 7 Buffer Solution: 0.025 M Phosphate: Potassium dihydrogen phosphate (KH2P04, 2.27 g) was dissolved with water to a volume of 250 ml (2.96 g). In a second vessel, 2.96 g of anhydrous disodium hydrogen phosphate (Na2HP04) was dissolved with water to a total volume of 250 ml. Combination of 155 ml KH2P04 solution and 223 ml Na2HPO4 solution with 622 ml water resulted in 0.025 M phosphate buffer at a final pH of 7.10 (as determined by pH meter).

Details on test conditions:

TEST SYSTEM
- Type, material and volume of test flasks: Autoclavable 30 mL screw cap graduated test tubes with Teflon® lined caps
- Lighting: Incubation chamber was maintained in the dark, except for sampling points and system checks.
- Measures taken to avoid photolytic effects: vials wrapped in aluminum foil
- If no traps were used, is the test system closed/open? Open
TEST MEDIUM
- Volume used/treatment: 20.2 mL
- Kind and purity of water: Water used in the study was deionized and purified using a Millipore ultrafiltration system fitted with three de-ionizing cartridges and one charcoal filter (model no. 12047-C).
- Preparation of test medium: The radiochemical was applied by pipetting 200 µL of 0.03 mg test substance/mL stock solution into 20.0 mL of buffer solution giving a final concentration of 0.3 ug/mL H20 with 1% (v/v) dimethyl formamide.

Duration:

5 d

pH:

4

Temp.:

50 °C

Duration:

30 d

pH:

5

Temp.:

25 °C

Duration:

28 d

pH:

5

Temp.:

40 °C

Duration:

5 d

pH:

6

Temp.:

25

Duration:

30 d

pH:

7

Temp.:

25

Duration:

29 d

pH:

9

Temp.:

25

Number of replicates:

2

Transformation products:

yes

No.:

#1

Details on hydrolysis and appearance of transformation product(s):

- Formation and decline of each transformation product during test: The safener AE F122006 was hydrolyzed rapidly under basic conditions with a
half-life in the order of minutes. Under more acidic conditions the rate of hydrolysis was slowed, to give a half-life of 98.6 days at pH 5 and 25 °C. The
graphical plot of Ln [%AE F122006] against time was in all cases a straight line with a correlation coefficient of 0.992 or greater. This demonstrated that first order kinetics was in operation at all temperatures and pH values studied.
- Pathways for transformation: The hydrolytic mechanism was a simple de-esterification and the free acid (AE F129431) was the only significant hydrolysis product found at any pH or temperature.
- Other: Less than 1 % of any additional component was present in any sample and consequently AE F129431 appeared to be relatively stable under the conditions studied.

% Recovery:

>= 92.2 - <= 99.4

pH:

4

Temp.:

50 °C

Duration:

5 d

% Recovery:

>= 101.9 - <= 104.1

pH:

5

Temp.:

40 °C

Duration:

28 d

% Recovery:

>= 95.8 - <= 99.6

pH:

5

Temp.:

25 °C

Duration:

30 d

% Recovery:

>= 100.1 - <= 100.6

pH:

6

Temp.:

25 °C

Duration:

5 d

% Recovery:

>= 102.4 - <= 103.2

pH:

7

Temp.:

25 °C

Duration:

30 d

% Recovery:

>= 102.1 - <= 102.3

pH:

9

Temp.:

25 °C

Duration:

29 d

pH:

4

Temp.:

50 °C

Hydrolysis rate constant:

0.001 d-1

DT50:

21 d

Type:

other: natural logarithm of percent AE F122006 remaining against time

pH:

5

Temp.:

40 °C

Hydrolysis rate constant:

0.007 d-1

DT50:

98.6 d

Type:

other: natural logarithm of percent AE F122006 remaining against time

pH:

5

Temp.:

25 °C

Hydrolysis rate constant:

0.045 d-1

DT50:

15.7 d

Type:

other: natural logarithm of percent AE F122006 remaining against time

pH:

6

Temp.:

25 °C

Hydrolysis rate constant:

0.039 d-1

DT50:

17.7 d

Type:

other: natural logarithm of percent AE F122006 remaining against time

pH:

7

Temp.:

25 °C

Hydrolysis rate constant:

0.279 d-1

DT50:

2.3 d

Type:

other: natural logarithm of percent AE F122006 remaining against time

pH:

9

Temp.:

25 °C

Hydrolysis rate constant:

32.82 d-1

DT50:

0.021 d

Type:

other: natural logarithm of percent AE F122006 remaining against time

Details on results:

TEST CONDITIONS
- pH, sterility, temperature, and other experimental conditions maintained throughout the study: Yes
- Anomalies or problems encountered: a single Day 0 replicate of the pH 5 at 25 °C hydrolysis set was anomalously low

MAJOR TRANSFORMATION PRODUCTS
At pH5:
- Range of maximum concentrations in % of the applied amount and day(s) of incubation when observed: at 25°C: 0.5, 5.8, 9.9, 13.7 on the zeroth, the 7th, the 14th and 21st day of incubation, respectively; at 40°C: 0.3, 25.6, 58.5, 70.2 on the zeroth, the 7th, 14th,21st and 28th day of incubation, respectively
- Range of maximum concentrations in % of the applied amount at end of study period: At the end of the study period, the corresponding concentrations were 98.1 and 97.8% of the applied amount at 25°C and 40°C and on day 30 or 28, respectively.

At pH7:
- Range of maximum concentrations in % of the applied amount and day(s) of incubation when observed: 0.3, 4.4, 8, 28.6, 88.1, 96, 97.5% in the zeroth hour, after 3 hours, after 6 hours, on the 1st, the 7th, 14th, 21st and 28th day of incubation, respectively.
- Range of maximum concentrations in % of the applied amount at end of study period: At the end of the study period, the corresponding concentration was 96.8% of the applied amount.

At pH9:
- Range of maximum concentrations in % of the applied amount and day(s) of incubation when observed: 0.8, 94.7, 95.9, 98.5, 97.3 in the zeroth, thesecond hour, on the 1st, 8th, and 15th day of incubation, respectively.
- Range of maximum concentrations in % of the applied amount at end of study period: At the end of the study period, the corresponding concentrations was 98.2% of the applied amount.

UNIDENTIFIED RADIOACTIVITY (at end of study)
- at pH5: at 25°C: 1.9 %; at 40 °C: 2.2%
- at pH7: 2.2%
- at pH9: 1.7 %

Validity criteria fulfilled:

not applicable

Description of key information

DT50: 2.3 days (pH 7, 25 °C) (OECD 111, EPA Guideline Subdivision N 161-1)

Additional information

One GLP guideline study on the hydrolytic degradation according to EPA guideline N, Series 161 -1 is available. The substance hydrolysed rapidly to its free acid under basic conditions with a half-life on the order of minutes (DT50 of 0.021 d at pH 9 and 25°C). Under more acidic conditions the rate of hydrolysis was reduced, such that the half-life at pH 5 and 25 °C was approximately 98.6 days. At the environmental relevant pH 7, the DT50 of the target compound is 2.3 days (25 °C).

De-esterification was the only significant hydrolysis mechanism found at any pH or temperature and the free acid was quite stable under the conditions of this investigation. Further transformation products were negligible.