5,7-dichloro-4-(4-fluorophenoxy)quinoline;quinoxyfen (ISO)

Hydrolysis

Link to relevant study record(s)

Reference

Reference 1

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:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

Test substance name: Radiolabelled DE-795
Batch No: GHD-3058-19
Radiochemical purity: > 97%

Radiolabelling:

yes

Analytical monitoring:

yes

Details on sampling:

- Sampling intervals for the parent/transformation products: Duplicate hydrolysis samples of each test system were taken for analysis at Day 0, 2 days and 5 days after treatment.
- Sampling method: Duplicate samples for each buffer and each time point were treated with 14C-labelled test substance at a concentration of ca 0.5 µg/ml, with acetone present as a 1% v/v co-solvent. Similarly, duplicate samples for each buffer and each time point were treated with 14C-labelled test substance at a concentration of ca 0.06 µg/ml with THF present as a 0.03% v/v co-solvent. The treated hydrolysis samples were then incubated at 50°C in the dark and sampled at intervals up to 5 days for analysis.

Buffers:

- pH: 4
- Type and final molarity of buffer: Pthalate and citrate
- Composition of buffer: The composition of buffer and co-solvents used is given in Table-1 under any other information on materials and methods including tables. The solubility of test substance in buffer solution was estimated at 1 µg/mL. The highest nominal concentration chosen to be used in this hydrolysis study was 0.5 µg/mL, which is below this solubility value.

Details on test conditions:

TEST SYSTEM
- Type, material and volume of test flasks: Volumetric flask (10 ml capacity for 1 and 3 treatments and 50 ml capacity for 2 and 4 treatments) and and the empty glass vial or jar washed with acetone (2-5 ml), which was also added to the volumetric flask.
- Sterilisation method: Autoclaving

TEST MEDIUM
- Volume used/treatment: For test groups 1 & 3: 8 mL of buffer was added to 74 µL of 14C-labelled test substance; For test groups 2 & 4: 45 ml of the respective buffer was added 12.3 µL of the 14C-labelled test substance.
- Identity and concentration of co-solvent: 1% v/v acetone and 0.03% v/v tetrahydrofuran (THF)

OTHER TEST CONDITIONS
- Adjustment of pH: Yes

Duration:

5 d

pH:

4

Temp.:

50 °C

Remarks:

Two concentrations were measured 0.5 µg/mL and 0.06 µg/mL

Number of replicates:

1

Negative controls:

yes

Transformation products:

yes

Remarks:

5,7-dichloro-4-hydroxy quinoline (DCHQ)

No.:

#1

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

- Formation and decline of each transformation product during test: Incubation of the samples at pH 4 and 50°C for 2 days resulted in the formation of a peak corresponding to DCHQ which accounted for between 21.1 and 29% of the total radioactivity recovered (TRR). For samples that had been incubated for 5 days at pH 4 and 50°C the relative proportion of DCHQ had increased to between 45.4 and 60.7% of the TRR
- Pathways for transformation: Hydrolysis

pH:

4

Temp.:

50 °C

Duration:

5 d

Remarks on result:

other: Recoveries were lower in the Day 5 samples in particular for the 0.06 µg/mL samples (70.1-81.4% recovery) as compared to the 0.5 µg/mL samples (86.4-102.5% recovery).

Key result

pH:

4

Temp.:

50 °C

DT50:

5 d

Details on results:

TEST CONDITIONS
- pH, sterility, temperature, and other experimental conditions maintained throughout the study: The desired test conditions were maintained throughout the 5 day incubation period. The pH during incubation did not range by more than ±0.4 from the initial pH values of 4.01 (phthalate buffer) and 3.99 (citrate buffer). The temperature range during incubation at 50°C did not vary by more than ±1°C from the nominal values throughout.

MAJOR TRANSFORMATION PRODUCTS
The HPLC results showed that the Day 0 samples only contained test substance. Incubation of the samples at pH 4 and 50°C for 2 days resulted in the formation of a peak corresponding to DCHQ which accounted for between 21.1 and 29% of the total radioactivity recovered. For hydrolysis samples that had been incubated for 5 days at pH 4 and 50°C the relative proportion of DCHQ had increased to between 45.4 and 60.7% of the TRR. These results clearly indicate that test substance is hydrolysed at pH 4 and 50°C in all test groups investigated giving an approximate half life of about five days irrespective of buffer type, initial test substance concentration, and the co-solvent used.

Validity criteria fulfilled:

yes

Conclusions:

Approximate half life: 5 Days (pH 4 and 50°C)

Executive summary:

The test was conducted according to OECD guideline 111 to evaluate the effect of buffer and Co-solvent on the hydrolysis of test substance. The hydrolysis of test substance was studied at pH4, with two different buffers (phthalate and citrate), two different concentrations of 14C labelled test substance (0.5 µg/mL and 0.06 µg/mL) and two different co-solvents (acetone and THF), under sterile conditions.

Duplicate samples for each buffer and each time point were treated with 14C labelled test substance at a concentration of ca 0.5 µg/ml, with acetone present as a 1% v/v co-solvent. Similarly, duplicate samples for each buffer and each time point were treated with 14C labelled test substance at a concentration of ca 0.06 µg/mL with THF present as a 0.03% v/v co-solvent. The treated hydrolysis samples were then incubated at 50°C in the dark and sampled at intervals up to 5 days for analysis. Work conducted for a previous hydrolysis study, showed some adsorption of radioactivity occurred to the glass test apparatus and so the analytical procedure used in this study was designed to account for this.

A radiochemical balance of 89.2-111.5% was shown throughout the day 0 and day 2 samples. Recoveries were lower in the day 5 samples in particular for the 0.06 µg/mL samples (70.1- 81.4% recovery) as compared to the 0.5 µg/mL samples (86.4 - 102.5% recovery).

The HPLC analysis of the extracted radioactivity showed that the Day 0 samples only contained test substance. Incubation of the samples at pH 4 and 50°C for 2 days resulted in the formation of a peak corresponding to DCHQ (5,7-dichloro-4-hydroxy quinoline) which accounted for between 21.1 and 29% of the total radioactivity recovered (TRR). For samples that had been incubated for 5 days at pH 4 and 50°C the relative proportion of DCHQ had increased to between 45.4 and 60.7% of the TRR. These results clearly indicate that, in all the test groups investigated, test substance is hydrolyzed at pH 4 and 50°C. Results of this study have also demonstrated that test substance is hydrolyzed at pH 4 giving an approximate half-life of about five days irrespective of buffer type, initial test substance concentration, and the co-solvent used.

Reference 2

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:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA Guideline Subdivision N 161-1 (Hydrolysis)

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: EEC method C.10

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

Test substance name: XDE 795 (PURE)
Batch Number: TSN 100004
Purity: 99.7%

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

Aliquots (500 ml) of each buffer solution were measured into reagent bottles, purged with nitrogen, sealed and placed in a thermostatically controlled oven at 50°C in the dark. When the buffer solutions had equilibrated at the temperature of the oven they were fortified with an aliquot (150 µL) of a stock solution (200.6 mg/L) of test substance in THF to give a nominal concentration of approximately 60 µg/L. The bottles were transferred back to the oven and held in the dark until sampling was required (after a short incubation period (approximately 10 minutes, then 2.4 h, 96 h (4 days) and 120 h (5 days)}. The oven was monitored during the period of the test to ensure that the test temperature was maintained.
On each sampling occasion, duplicate aliquots (10 ml) were removed, 5M hydrochloric acid (100 mL) was added to each sample, and the concentration of test substance was determined by direct injection using HPLC with ultraviolet detection. The pH was determined over the period of the test.

Buffers:

- pH: 4, 7 & 9
- Composition of buffer: Buffer solutions were prepared using the following volumes:
pH 4.0: Disodium hydrogen orthophosphate dodecahydrate (27.6 g) and citric acid monohydrate (12.9 g) were dissolved in distilled water (1900 ml) and the pH was adjusted to 4.0 with 1M hydrochloric acid or 1M sodium hydroxide. The volume was adjusted to 2000 ml with distilled water.
pH 7.0: Potassium dihydrogen orthophosphate (6.8 g) was dissolved in distilled water (1900 ml), 1M sodium hydroxide (30 ml) was added and the pH was adjusted to 7.0 with 1M hydrochloric acid or 1M sodium hydroxide. The volume was adjusted to 2000 ml with distilled water.
pH 9.0: Disodium tetraborate decahydrate (33.1 g) and potassium dihydrogen orthophosphate (3.59 g) were dissolved in distilled water (1900 ml) and the pH was adjusted to 9.0 with 1M hydrochloric acid, or 1M sodium hydroxide. The volume was adjusted to 2000 ml with distilled water.

Details on test conditions:

TEST SYSTEM
- Type used: Reagent bottle
TEST MEDIUM
- Volume used/treatment: Buffer solution (150 µL)
- Identity and concentration of co-solvent: Tetrahydro fluran (THF)
OTHER TEST CONDITIONS
- Adjustment of pH: Yes

Duration:

5 d

Temp.:

50 °C

Initial conc. measured:

60 µg/L

Remarks:

At pH 4, 7 and 9

Number of replicates:

1

Transformation products:

no

Key result

Temp.:

50 °C

Remarks on result:

other: The hydrolysis rates at pH 4, 7 and 9 and 50°C were such that less than 10% hydrolysis was observed at 5 days.

Remarks:

This is equivalent to environmental half-lives of greater than 1 year.

Details on results:

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

Result: There was no significant change in the concentration of test substance when incubated in pH 4, 7 and 9 buffer solutions at 50°C. As the degree of degradation of test substance was less than 10% after 5 days (equivalent to an environmental half-life of greater than 1 year) further testing was not necessary.

Validity criteria fulfilled:

yes

Conclusions:

Test substance is hydrostatistically stable under acidic, neutral and basic conditions.

Executive summary:

The test was conducted according to OECD guideline 111 to evaluate hydrolysis of test substance as a function of pH.

The preliminary study showed that after 5 days at pH 4, 7 and 9 and 50°C less than 10% hydrolysis had occurred (t1/2 >1 year) at all three pH values, thus no further testing was necessary.

Under the conditions of the study, the test substance is hydrostatistically stable under acidic, neutral and basic conditions.

Reference 3

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:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

Radiolabelled test substance name: 14C-XDE-795
Batch ID: GHD-3058-19
Radiopurity: >99%

Non-Radiolabelled test substance name: XDE-795
Batch ID: 597-92G-31C18557

Radiolabelling:

yes

Remarks:

[14C]-test substance labelled at position 2 of the quinoline ring

Analytical monitoring:

yes

Details on sampling:

For the preliminary test at 50°C, duplicate hydrolysates at each pH were removed for analysis at 0, 2, 5 and 21 days after treatment (DAT). At pH 4, only a single sample was taken at 21 DAT, in addition to one at 12 DAT. The 21 DAT samples were stored in the dark at <-16°C prior to analysis. For the further work at pH 4 and 25°C, duplicate samples were taken at 0, 3, 7, 14, 21, 30 and 46 DAT, whilst those at 40°C were additionally sampled at 1 and 24 DAT, but not at 46 DAT.
For the preparative hydrolysis the entire sample was taken for analysis at 25 DAT

Buffers:

- pH: 4, 7 and 9
- Type and final molarity of buffer: The overall buffer concentrations did not exceed 0.05M
- Composition of buffer: The composition of buffers at pH 4, 7 and 9 are in given in table-1 under "any other information on materials and methods including tables". Prior to
use the prepared buffers were sterilised by autoclaving for a minimum of 15 minutes at 121°C and ca 2 bar. Autoclave tape was used to indicate that successful sterilisation had taken place.

Details on test conditions:

TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: 10mL volumetric flask
- Sterilisation method: Autoclaving

TEST MEDIUM
- Volume used/treatment Buffer & water
- Kind and purity of water: Single-distilled

Duration:

21 d

Temp.:

50 °C

Initial conc. measured:

0.5 other: µg/mL

Remarks:

At pH 4, 7 & 9, Preliminary test

Duration:

46 d

pH:

4

Temp.:

25 °C

Initial conc. measured:

0.5 other: µg/mL

Remarks:

Main test

Duration:

24 d

pH:

4

Temp.:

40 °C

Initial conc. measured:

0.5 other: µg/mL

Remarks:

Main test

Number of replicates:

1 for both main and preliminary test

Negative controls:

yes

Transformation products:

yes

Remarks:

5,7-dichloro-4-hydroxyquinoline (DCHQ)

No.:

#1

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

The results showed that in the pH 4 hydrolysate at 50°C, test substance degraded to give a single component that matched DCHQ by HPLC, and accounted for ca 90% of the radioactivity present in the sample at 21 days of treatment (DAT). However, degradation was less extensive in the adsorbate, suggesting that the radioactivity associated with the glass was less readily available for hydrolysis. At pH 7 and 50°C, only minimal degradation occurred in the hydrolysate (up to 4% at 21 DAT) with none seen in the adsorbate except in one 21 DAT sample (0.6%). At pH 9, little or no degradation was observed in either hydrolysate or adsorbate.

Key result

pH:

4

Temp.:

50 °C

DT50:

1 wk

Remarks on result:

other: Preliminary test

Key result

pH:

4

Temp.:

25 °C

DT50:

11 wk

Remarks on result:

other: Main study

Key result

pH:

4

Temp.:

40 °C

DT50:

2 wk

Remarks on result:

other: Main study

Key result

Temp.:

50 °C

Remarks on result:

other: The test substance is stable at pH 7 & 9.

Remarks:

Preliminary test

Other kinetic parameters:

Adsorption of radioactivity to glass was observed under the test conditions. This was generally <10% of applied at pH 4, but increased at pH 7 (up to 22%) and pH 9 (up to 33%). When this is taken into account, a radiochemical balance (95- 109%) was achieved for all samples.

Details on results:

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

MAJOR TRANSFORMATION PRODUCTS
At pH 4: In preliminary study, At 50°C, test substance degraded at pH 4 with a t1/2 of ca 1 week to give a single product which was shown by spectroscopic analysis to be 5,7-dichloro-4-hydroxyquinoline (DCHQ). In main study, at pH 4, test substance degraded at 25°C with a t1/2 of 11 weeks, decreasing to ca 2 weeks at 40°C. DCHQ was the hydrolysis product.

At pH 7 & pH 9: At 50°C and pH 7 and pH 9 only 1% degradation or less occured after 5 days incubation. The very limited degradation at pH 7 and pH 9 under the preliminary test conditions meant that test substance was defined by the guideline as hydrolytically stable (t1/2 >1 year), and therefore no further testing was done at pH 7 or pH 9.

Validity criteria fulfilled:

yes

Conclusions:

At pH 4, test substance degraded at 25°C with a t1/2 of 11 weeks, decreasing to ca 2 weeks at 40°C. 5,7-dichloro-4-hydroxyquinoline (DCHQ) was the hydrolysis product.

Executive summary:

The test was conducted according to guideline OECD 111 to determine hydrolysis of test substance at pH 4, pH 7 and pH 9 under sterile conditions. Portions of each buffer were treated with quinoline-14C-labelled test substance at a nominal concentration of 0.5 µg/mL, with acetone present as a 1% v/v co-solvent. The hydrolysates were then incubated at 50°C in the dark and sampled at intervals for analysis. The results showed that test substance was stable at pH 7 and pH 9 under these conditions, but degraded at pH 4 to give 5,7-dichloro-4-hydroxyquinoline (DCHQ), with a t1/2 of ca 1 week.

Further work carried out at pH 4 and 25°C and 40°C, showed that test substance degraded with t1/2 of ca 11 and 2 weeks respectively, with DCHQ as the hydrolysis product. No further testing was done at pH 7 or pH 9.

Under the study conditions some adsorption of radioactivity to glass was observed. This was generally <10% of applied at pH 4, but increased at pH 7 (up to 22%) and pH 9 (up to 33%). When this is accounted for, a radiochemical balance (95-109%) was achieved for all samples.

Description of key information

No significant hydrolytic degradation was observed to occur in pH buffers 5, 7 or 9 at 50°C. Less than 10% hydrolysis was observed at 5 days which by the guidelines defines the substance as hydrolytically stable (t1/2> 1 year). In another test at pH 4,the test substance degraded at 25°C with a t1/2 of 11 weeks, decreasing to ca 2 weeks at 40°C. In a third test, the half-life at pH 4 and 50°C was 5 days. 5,7-dichloro-4-hydroxyquinoline (DCHQ) was found to be the hydrolysis product.

Key value for chemical safety assessment

Half-life for hydrolysis:

11 wk

at the temperature of:

25 °C