Methyl O-(4-amino-3,5-dichloro-6-fluoropyridin-2-yloxy)acetate

Hydrolysis

Administrative data

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

9 May - 30 September 1991

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: GLP-Guideline study with acceptable restrictions (no information on transformation products)

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1991

Report date:

1991

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other: 84/449/EEC, Annex V, Method C10. Adopted in 1984

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Methyl O-(4-amino-3,5-dichloro-6-fluoropyridin-2-yloxy)acetate

EC Number:

407-550-4

EC Name:

Methyl O-(4-amino-3,5-dichloro-6-fluoropyridin-2-yloxy)acetate

Cas Number:

69184-17-4

Molecular formula:

Hill formula: C8 H7 Cl2 F N2 O3 CAS formula: C8 H7 Cl2 F N2 O3

IUPAC Name:

methyl 2-[(4-amino-3,5-dichloro-6-fluoropyridin-2-yl)oxy]acetate

Details on test material:

- Name of test material (as cited in study report): Fluroxypyr methyl ester (technical)
- Substance type: technical product
- Physical state: solid, fine, black, crystalline powder
- Analytical purity: 90.8% w/w
- Lot/batch No.: C-3B

Radiolabelling:

no

Study design

Analytical monitoring:

yes

Details on sampling:

- Sampling intervals for the parent compound: minimum 6 times per group
- Sampling method:
Preliminary study: duplicate aliquots (1 mL) were removed and diluted to 10 mL with acetonitrile/0.1M orthophosphoric acid (60:40 v/v) and analysed by HPLC
Definitive study: duplicate aliquots were removed from each test solution and directly analysed by HPLC
- Sampling intervals/times for pH measurements: pH values of each test solution were measured at the beginning and at the end of the test period in both preliminary and definitive tests

Buffers:

- pH: 4
Disodium hydrogen phosphate 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 1 M hydrochloric acid or 1 M sodium hydroxide. The volume was adjusted to 2000 mL with distilled water
- pH: 7
Potassium dihydrogen phosphate (6.8 g) was dissolved in distilled water (1900 mL), 1 M sodium hydroxide (30 mL) was added and the pH was adjusted to 7.0 with 1 M hydrochloric acid or 1 M sodium hydroxide. The volume was adjusted to 2000 mL with distilled water
- pH 9
Disodium tetraborate decahydrate (33.1 g) and potassium dihydrogen phosphate (3.59 g) were dissolved in distilled water (1900 mL) and the pH was adjusted to 9.0 with 1 M hydrochloric acid, or 1 M sodium hydroxide. The volume was adjusted to 2000 mL with distilled water

Details on test conditions:

- Preliminary study: Samples (250 mL) of each buffer solution were measured into Pyrex bottles, purged with nitrogen, sealed and placed in a thermostatically controlled oven at 50 °C in the dark. Once the buffer solutions had equilibrated to the temperature of the oven they were fortified with an aliquot (100 µL) of a stock solution (4.88 mg/mL) of the test substance in acetonitrile to give a nominal test solution concentration of 1.95 mg/L. The bottles were transferred back to the oven and held in the dark until sampling was required. The oven was monitored during the period of the test to ensure that the test temperature was maintained

- Definitive study: three samples of pH4 and three samples of pH7 buffer solutions (250 mL) were measured into Pyrex bottles, purged with nitrogen, sealed and one sample placed in each of three thermostatically controlled areas (a water bath at 50 °C, a water bath at 60 °C and an oven at 70 °C) in the dark. Once the buffer solutions had equilibrated to the respective test temperatures they were fortified with aliquots (100 µL) of a stock solution (4.96 mg/mL) of the test substance in acetonitrile to give a nominal test solution concentration of 1.99 mg/L. The pH7 buffer solutions equilibrated at 60°C and 70°C were fortified with aliquots (100 µL) of a stock solution (5.11 mg/mL) of the test substance in acetonitrile to give a nominal test solution concentration of 2.05 mg/L. The bottles were transferred back to their respective storage areas and held in the dark until sampling was required. The water baths and oven were monitored during the period of the test to ensure that the test temperatures were maintained

Duration of test

Duration of test 1

Duration:

120 h

pH:

4

Temp.:

50 °C

Initial conc. measured:

1.91 mg/L

Duration of test 2

Duration:

120 h

pH:

7

Temp.:

50 °C

Initial conc. measured:

1.93 mg/L

Duration of test 3

Duration:

120 h

pH:

9

Temp.:

50 °C

Initial conc. measured:

1.59 mg/L

Duration of test 4

Duration:

497 h

pH:

4

Temp.:

50 °C

Initial conc. measured:

1.91 mg/L

Duration of test 5

Duration:

261 h

pH:

4

Temp.:

60 °C

Initial conc. measured:

1.84 mg/L

Duration of test 6

Duration:

214 h

pH:

4

Temp.:

70 °C

Initial conc. measured:

1.88 mg/L

Duration of test 7

Duration:

11 h

pH:

7

Temp.:

50 °C

Initial conc. measured:

1.84 mg/L

Duration of test 8

Duration:

7

pH:

7

Temp.:

60 °C

Initial conc. measured:

1.78 mg/L

Duration of test 9

Duration:

4.67 h

pH:

7

Temp.:

70 °C

Initial conc. measured:

1.81 mg/L

Number of replicates:

1 replicate per pH and temperature value

Results and discussion

Preliminary study:

The results from the preliminary test showed that after after 2.4 hours at pH 9 and 50 °C the test substance hydrolized by more than 50%, whereas it did not at pH 4 and 7 at the same temperature. However, at pH 4 and 7 more than 10% hydrolysis took place and therefore, additional testing at these two pH conditions was necessary

Transformation products:

not specified

Dissipation DT50 of parent compound

Dissipation DT50 of parent compound 1

pH:

4

Temp.:

25 °C

Hydrolysis rate constant:

0 h-1

DT50:

356 d

Type:

(pseudo-)first order (= half-life)

Dissipation DT50 of parent compound 2

pH:

7

Temp.:

25 °C

Hydrolysis rate constant:

0.006 h-1

DT50:

4.8 d

Type:

(pseudo-)first order (= half-life)

Any other information on results incl. tables

Table 1. Results of the definitive hydrolysis test of Fluroxypyr methyl ester (technical)

pH	Temperature	Slope of log linear regression (x10^3)	Kobs (x10^3)	t1/2
4	50	-0.409	0.942	735
4	60	-0.665	1.53	453
4	70	-2.09	4.82	144
7	50	-19.5	44.9	15.4
7	60	-31.6	72.7	9.53
7	70	-75.5	174	3.99