Phosphonic acid, monoethyl ester, sodium salt (1:1)

Hydrolysis

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

hydrolysis

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

20 Mar - 26 Mar 2001

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)

Qualifier:

according to guideline

Guideline:

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

GLP compliance:

yes

Radiolabelling:

no

Analytical monitoring:

yes

Buffers:

A series of 0.05 M buffer solutions were prepared using double distilled water as follows:#

pH 4.0: 0.05 M potassium biphthalate adjusted to pH 4.0 with 1 N sodium hydroxide
pH 7.0: 0.05 M boric acid adjusted to pH 7.0 with 1 N sodium hydroxide solution
pH 9.0: 0.05 M boric acid adjusted to pH 9.0 with 1 N sodium hydroxide solution

The pH of the buffer solutions was measured using a Griffin pH meter Model 50 with pH probe (Fisher Scientific, Loughborough, Leics.) calibrated to pH 4 and 7 or 7 and 10, as appropriate, using standard pH solutions.
Nitrogen was bubbled through the buffer solutions for approximately 30 minutes to reduce the oxygen content. The oxygen content was measured using a Jenway 9071 dissolved oxygen meter.

Details on test conditions:

TEST SYSTEM
- Type, material and volume of test flasks, other equipment used:
- Sterilisation method: The glass ware and associated equipment required for the test were autoclaved at 121 °C and 15 lb/in2 for 15 minutes prior to use. The buffer solutions were sterilised by filtration through 0.2 µm sterile filters. All procedures involving preparation of the test system (for example, filtration of the buffer and preparation of test solutions) were conducted in a laminar flow cabinet to ensure maintenance of sterility. Sterility of the test solutions was not demonstrated during this preliminary test. However, sterility was demonstrated on a portion of filtered untreated buffer solution.
TEST MEDIUM
- Volume used/treatment: The test solution concentration is required to be less than half the water solubility, which for fosetyl-Al is 120g/L . The nominal test solution concentration selected for the study was 100mg/L.
- Preparation of test medium: Bulk test solutions at each pH were prepared by dissolving portions (10.1 mg) of Fosetyl-Al in each buffer solution and diluting to volume (100mL) with the appropriate buffer solution. Portions (approximately 30 mL) of the test solutions were then dispensed into individual vessels (30mL borosilicate glass vials with PTFE lined crimped caps).

Duration:

5 d

pH:

4

Temp.:

50 °C

Initial conc. measured:

100 mg/L

Duration:

5 d

pH:

7

Temp.:

50 °C

Initial conc. measured:

100 mg/L

Duration:

5 d

pH:

9

Temp.:

50 °C

Initial conc. measured:

100 mg/L

Positive controls:

no

Negative controls:

no

Transformation products:

no

pH:

4

Temp.:

50 °C

Remarks on result:

hydrolytically stable based on preliminary test

Remarks:

Test was conducted over 5 days

pH:

7

Temp.:

50 °C

Remarks on result:

hydrolytically stable based on preliminary test

Remarks:

Test was conducted over 5 days

pH:

9

Temp.:

50 °C

Remarks on result:

hydrolytically stable based on preliminary test

Remarks:

Test was conducted over 5 days

Details on results:

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

Achieved application:

Test systems were required to be fortified at a concentration equal to less than half of the reported water solubility of 120g/L. The nominal concentration chosen for the test systems was 100 mg/L. The achieved application rate was 90.4 mg/L, which is equivalent to 90.4% of nominal (this was based on the mean of the T0 samples).

Test system monitoring:

The pH values of the buffer solutions following sterilisation and prior to fortification were within ± 0.06 pH units of the nominal values. The pH of the test solutions was measured at each sampling occasion and were found to be within ± 0.48 pH units of the nominal values. The temperature was measured continuously and was in the range 48.9 to 50.3 °C throughout the period of the test.

Hydrolysis of Fosetyl-Al:

At pH 4, the concentration of Fosetyl-Al in solution, was essentially unchanged from 82.4 mg/L at T0 to 83.7 mg/L at 5 days. Therefore, at pH 4, no hydrolysis of Fosetyl-Al was detected after 5 days at 50 °C.

At pH 7, the concentration of Fosetyl-Al in solution, was essentially unchanged from 100.3 mg/L at T0 to 102.0 mg/L at 5 days. Therefore, at pH 7, no hydrolysis of Fosetyl-Al was detected after 5 days at 50 °C.

At pH 9, the concentration of Fosetyl-Al in solution, was essentially unchanged from 88.5 mg/L at T0 to 90.9 mg/L at 5days. Therefore, at pH 9, no hydrolysis of Fosetyl-Al was detected after 5 days at 50° C.

No hydrolysis of Fosetyl-Al was detected at pH 4, 7 and 9, each at 50 °C, during and after a 5 day test period. Fosetyl-Al is therefore considered to be hydrolytically stable and no additional investigations were conducted.

Table: Concentration of Fosetyl-Al in the buffer solutions treated with Fosetyl-Al and incubated at 50 °C at each pH on each sampling occasion in the preliminary test

pH	Fosetyl-Al detected (mg/L)
	day 0	2 days	5 days
4	82.4	83.7	83.7
7	100.3	102.1	102.0
9	88.5	90.0	90.9

Validity criteria fulfilled:

not applicable

Reference 2

Endpoint:

hydrolysis

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

Refer to analogue justification provided in IUCLID section 13

Reason / purpose for cross-reference:

read-across source

Transformation products:

no

pH:

4

Temp.:

50 °C

Remarks on result:

hydrolytically stable based on preliminary test

Remarks:

Test was conducted over 5 days

pH:

7

Temp.:

50 °C

Remarks on result:

hydrolytically stable based on preliminary test

Remarks:

Test was conducted over 5 days

pH:

9

Temp.:

50 °C

Remarks on result:

hydrolytically stable based on preliminary test

Remarks:

Test was conducted over 5 days

No hydrolysis of Fosetyl-Al was detected at pH 4, 7 and 9, each at 50 °C, during and after a 5 day test period. Fosetyl-Al is therefore considered to be hydrolytically stable and no additional investigations were conducted.

Validity criteria fulfilled:

not applicable

Description of key information

No hydrolysis at 50 °C in aqueous solution at pH 4, 7 and 9 after 5 days.

Additional information

No studies on hydrolysis are available for the target substance Fosetyl-sodium (CAS 39148-16-8). Therefore, this endpoint is covered by read-across to the analogous substance Fosetyl-aluminium (CAS 39148-24-8). The source substance Fosetyl-aluminium is a long and widely used fungicide. The evaluation of the extensive data base available shows that Fosetyl-aluminium is of very low acute and chronic toxicity. The target substance is a pre-manufacturing product for the synthesis of Fosetyl-aluminium. Details on the read across justification can be found in IUCLID Section 13. 

A GLP study according to OECD guideline 111 on the hydrolysis has been carried out with Fosetyl-aluminium to determine the rate of hydrolysis in aqueous solutions at pH values normally found in the environment (pH 4, 7, and 9). A preliminary hydrolysis test was performed at 50 °C in aqueous solution at pH 4, 7, and 9. Under the conditions of the test no hydrolysis of Fosetyl-Al was detected. Fosetyl-Al is therefore considered to be hydrolytically stable. On the basis of the results from the preliminary test, no further work was conducted.

Based on the results with the source substance Fosetyl-Aluminium (CAS 39148-24-8), the target substance Fosetyl-Sodium (CAS 39148-16-8) is also considered to be hydrolytically stable.