α-n-butyl-α-(4-chlorophenyl)-1H-1,2,4-triazole-1-propanenitrile

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1993-09-20 to 1993-11-01

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

Guideline screening test, full study not required since hydrolysis not observed 50ºC.

Qualifier:

equivalent or similar to guideline

Guideline:

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

Version / remarks:

EC Directive 92/69/EEC (OJ no. L383A, 29.12.1992), Part C, Method C.7

Principles of method if other than guideline:

Only screening test was needed due to lack of hydrolysis at 50ºC.

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

Technical grade myclobutanil was prepared in solution at a concentration of 5015.5 µg/mL (solvent not specified in report), and an aliquot (1.0 mL) added to ca 98 mL of each buffer contained in a volumetric flask (100 mL capacity, pre-calibrated to give the correct volume at 50ºC). After making up to volume with the appropriate buffer at 50ºC to give a nominal myclobutanil concentration of 50.155 µg/mL, duplicate aliquots (20.0 mL) were removed as zero-time samples. Further duplicate aliquots of each buffer solution were also removed after 2.4 hours and 5 days incubation.

Blank samples were prepared in the same way containing buffer only (no test item).

At each sampling time, duplicate quality control solutions at each pH were prepared using analytical grade myclobutanil at a nominal concentration of 50 µg a.s./mL, and these samples were taken through the analytical procedure as recovery samples.

Buffers:

Aqueous buffer solutions at pH 4 (potassium dihydrogen citrate), pH 7 (potassium dihydrogen orthophosphate), and pH 9 (potassium chloride/boric acid/sodium hydroxide) were prepared and sterilised by autoclaving. The final pH was checked at 50ºC and adjusted if necessary.

Duration:

5 d

pH:

9

Temp.:

50 °C

Initial conc. measured:

ca. 50 mg/L

Remarks:

No significant hydrolysis of myclobutanil occurred over 5 days at pH 4, 7 and 9 and 50ºC.

Duration:

5 d

pH:

7

Temp.:

50 °C

Initial conc. measured:

ca. 50 mg/L

Remarks:

No significant hydrolysis of myclobutanil occurred over 5 days at pH 4, 7 and 9 and 50ºC.

Duration:

5 d

pH:

4

Temp.:

50 °C

Initial conc. measured:

ca. 50 mg/L

Remarks:

No significant hydrolysis of myclobutanil occurred over 5 days at pH 4, 7 and 9 and 50ºC.

Preliminary study:

No preliminary study was identified.

Transformation products:

no

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

The data showed that the measured zero time concentrations ranged from 96.5 to 104.8% of nominal, and that no significant hydrolysis of myclobutanil occurred over 5 days at pH 4, 7 and 9 and 50ºC.

% Recovery:

90.3

pH:

9

Temp.:

50 °C

% Recovery:

91

pH:

7

Temp.:

50 °C

% Recovery:

91.9

pH:

4

Temp.:

50 °C

Key result

pH:

9

Remarks on result:

other: Under the test conditions, the test item was found to undergo no hydrolysis.

Key result

pH:

4

Remarks on result:

other: Under the test conditions, the test item was found to undergo no hydrolysis.

Key result

pH:

7

Remarks on result:

other: Under the test conditions, the test item was found to undergo no hydrolysis.

Details on results:

The pH of all the test solutions remained constant throughout the duration of the test. Calibration data showed that the detector response was linear in the concentration range employed, with correlation coefficients of 0.999. The recovery of myclobutanil in the quality control solutions ranged from 85.8-100.9% at pH 4 (mean 91.9%), 89.8-92.6% at pH 7 (mean 91.0%), and 85.1-96.1% at pH 9 (mean 90.3%). No peaks were seen at the retention time (4.1 mins) of myclobutanil in the blank solutions, indicating no interference in the analytical method.

Myclobutanil was stable to hydrolysis under sterile conditions in pH 4, 7 and 9 buffers over 5 days at 50ºC, and therefore it is not meaningful to calculate any DT50 values. According to the test method, it can be concluded that the hydrolytic half-life of myclobutanil at 25ºC is >1 year.
Although not investigated as part of the study, it is expected that there are no hydrolysis products due to the minimal degradation.

Validity criteria fulfilled:

yes

Conclusions:

The data showed that the measured zero time concentrations ranged from 96.5-104.8% of nominal, and that no significant hydrolysis of myclobutanil occurred over 5 days at pH 4, 7 and 9 and 50ºC. According to the test method, it can be concluded that the half-life of myclobutanil is greater than one year at 25ºC.
Although not investigated as part of the study, it is expected that there are no hydrolysis products due to the minimal degradation.

Executive summary:

A study was performed to assess the abiotic degradation of RH-3866. The method followed was for the preliminary test described in the EEC Methods for determination of ecotoxicity, Directive 92/69/EEC (OJ No. L383A, 29.12.1992) Part C, Method C.7. Abiotic degradation: hydrolysis as a function of pH.
Hydrolysis was evaluated over 5 days at 50°C in aqueous solution at pH 4, 7 and 9. The starting concentration was ca. 50 µg/mL, a concentration that represented less than 0.01M. The concentration of RH-3866 was determined by HPLC analysis. Under the test conditions, RH-3866 was found to undergo no hydrolysis at pH 4, 7 or 9. The results indicate that at 25°C RH-3866 will possess half-life times of greater than one year at pH 4, 7 and 9.

Description of key information

The data of a GLP-study performed according to EU Method C.7, showed that no significant hydrolysis of myclobutanil occurred over 5 days at pH 4, 7 and 9 and 50ºC. According to the test method, it can be concluded that the half-life of myclobutanil is greater than one year at 25ºC.