5-amino-1-[2,6-dichloro-4-(trifluoromethyl)phenyl]-4-(ethylsulfinyl)-1H-pyrazole-3-carbonitrile

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

24 Jun - 01 Aug 1997

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EPA OPPTS 835.2120 (Hydrolysis of Parent and Degradates as a Function of pH at 25°C)

GLP compliance:

yes

Radiolabelling:

yes

Analytical monitoring:

yes

Details on sampling:

- Sampling intervals for the parent/transformation products: on days 0, 3, 6, 14, 21 and 31 for each pH test system
- Sampling method: At each timepoint, duplicate samples were removed from the test tubes and analysed
- Sampling intervals/times for pH measurements: Each sample was checked for pH.
- Sampling intervals/times for sterility check: On days 0 and 31, samples from all pH series were cultured on plates of Trypticase Soy Agar.
- Sample storage conditions before analysis: Samples were analysed on the day of harvest, with the exception of samples from day 31 being stored frozen for 4 days prior to analysis.

Buffers:

- pH: 4, 5, 7 and 9
- Type and final molarity of buffer: pH 4: 0.1 M Citrate, pH 5: 0.1 M Acetate, pH 7: 0.1 M Phosphate, pH 9: 0.01 M Borate

COMPOSITION OF BUFFERS
- pH 4 buffer solution: 1.071 g monosodium citrate, equivalent to 50 mL 0.1 M monosodium citrate, was mixed with 9.00 mL 0.1M NaOH; deionized water was added to a final volume of 100 mL.
- pH 5 buffer solution: 83.9 mL glacial acetic acid, equivalent to 14.6 mL 0.1 M acetic acid, was mixed with 10 mL of 0.1 M NaOH; deionized water was added to a final volume of 100 mL.
- pH 7 buffer solution: 2.24 mL of 0.1 M KH2PO4 was added to 2.58 mL of 0.1 M Na2HPO4; deionized water was added to a final volume of 100 mL.
- pH 9 buffer solution: 0.191 g sodium borate decahydrate, equivalent to 50 mL of 0.01 M Na2B4O7 x 10H2O, was mixed with 15.2 mL HCl, equivalent to 4.6 mL 0.04 M HC1; deionized water was added to a final volume of 100 mL.

Details on test conditions:

TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: 8 mL pyrex tubes with Teflon lined screw caps
- Sterilisation method: Buffer solutions were passed through a 0.22 µm filter, pyrex tubes were autoclaved
- Lighting: no, incubation in the dark
- If no traps were used, is the test system closed/open: closed

TEST MEDIUM
- Volume used/treatment: 5 mL
- Kind and purity of water: HPLC grade water or purified with a Barnstead Nano Pure II system
- Preparation of test medium: The test solutions were prepared by adding 245 µL (ca. 2.7 x 1E06 DPM) of [14C]RPA 107382 to 75 mL of each respective buffer. The resulting test solutions were mixed well and then radioassayed by liquid scintillation counting of three 100 µL aliquots. The applied concentrations were 3 ppm. For each pH, 5 mL aliquots of the test solution were dispensed into the test tubes.
- Identity and concentration of co-solvent: acetonitrile, < 1% of the final buffer volume

Duration:

31 d

pH:

4

Initial conc. measured:

3 other: ppm

Duration:

31 d

pH:

5

Initial conc. measured:

2.99 other: ppm

Duration:

31 d

pH:

7

Initial conc. measured:

2.94 other: ppm

Duration:

31 d

pH:

9

Initial conc. measured:

2.99 other: ppm

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 test substance did not degrade at pH 4, 5 or 7. In the pH 9 solution, the amide RPA 112916 was the only significant hydrolysis product detected representing 11.8% of the radiocarbon.
- Pathways for transformation: Hydrolysis of the nitrile group yields the amide.
- Other: After 31 days, 2.56 - 2.98% of any additional component was present in the samples incubated at pH 4, 5 and 7. In the pH 9 sample, 5.46% of any additional component was present.

% Recovery:

99.8

St. dev.:

2.1

pH:

4

Temp.:

25 °C

Duration:

31 d

% Recovery:

100.2

St. dev.:

1.3

pH:

5

Temp.:

25 °C

Duration:

31 d

% Recovery:

100.2

St. dev.:

1.4

pH:

7

Temp.:

25 °C

Duration:

31 d

% Recovery:

99.9

St. dev.:

1.3

pH:

9

Temp.:

25 °C

Duration:

31 d

pH:

9

Temp.:

25 °C

DT50:

121 d

Type:

other: natural logarithm of percent parent compound remaining against time

Details on results:

TEST CONDITIONS
- pH, sterility, temperature, and other experimental conditions maintained throughout the study: Yes
- pH variations: (pH 4) 3.99 - 4.02, (pH 5) 4.92 - 4.99, (pH 7) 6.99 - 7.08, (pH 9) 8.89 - 9.02

MAJOR TRANSFORMATION PRODUCTS
At pH9:
- Range of maximum concentrations in % of the applied amount and day(s) of incubation when observed: 0.9, 1.18, 4.28 and 8.24% on the 3rd, 6th, 14th and 21st 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 11.66 and 11.93 % of the applied amount, respectively.

Validity criteria fulfilled:

not applicable

Description of key information

Ethiprole is not hydrolytically degraded at pH 4, 5 or 7. At pH 9 the degradation half-life of the substance is 121 d.

Additional information

One GLP guideline study on the hydrolytic degradation of the substance at 25 °C according to EPA OPPTS 835.2120 is available. The substance did not hydrolyse at pH 4, 5 or 7. However, at pH 9 hydrolysis of the nitrile group was observed yielding the amide of the molecule. Under this condition, the dissipation half-life was determined as 121 d.