Methylphosphonic acid

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

13.02-30.04.2013

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:

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

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

no

Analytical monitoring:

no

Details on sampling:

- Sampling method: The samples were taken from the water bath at various times and the pH of each sample recorded.
- Sampling methods for the volatile compounds, if any: no
- Sampling intervals/times for pH measurements: 0, 24, 120 hours
- Other observation, if any (e.g.: precipitation, colour change etc.): no

Buffers:

-ph 4:
Potassium hydrogen phthalate 5 mmol dm-3
pH 7:
Disodium hydrogen orthophosphate (anhydrous) 3 mmol dm-3
Potassium dihydrogen orthophosphate 2 mmol dm-3
Sodium chloride 2 mmol dm-3
pH 9:
Disodium tetraborate 1 mmol dm-3
Sodium chloride 2 mmol dm-3

Details on test conditions:

TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: stoppered glass vessels
- Lighting: the solutions were shielded from light whilst maintained at the test temperature
- Measures taken to avoid photolytic effects: not reported
- Measures to exclude oxygen: ultrasonication and degassing with nitrogen
- Details on test procedure for unstable compounds: not applicable
- Details of traps for volatile, if any: not applicable
- If no traps were used, is the test system closed/open: closed
- Is there any indication of the test material adsorbing to the walls of the test apparatus? no
TEST MEDIUM
- Volume used/treatment: not reported
- Kind and purity of water: sterile buffer solution
- Preparation of test medium: Sample solutions were prepared in stoppered glass vessels at a nominal concentration of 400 mg/L in the three buffer solutions. The solutions were then adjusted to the respective nominal buffer solution pH, as necessary, with 0.1 M sodium hydroxide solution. The test solutions were split into individual vessels for each data point.
- Renewal of test solution: no
OTHER TEST CONDITIONS
- Adjustment of pH: adjusted to the respective nominal buffer solution pH, as necessary, with 0.1 M sodium hydroxide solution
- Dissolved oxygen: solutions were subjected to ultrasonication and degassing with nitrogen to minimize dissolved oxygen content

Duration:

0 h

pH:

4

Temp.:

50

Initial conc. measured:

0.378 mg/L

Duration:

0 h

pH:

4

Temp.:

50

Initial conc. measured:

0.391 mg/L

Duration:

0 h

pH:

7

Temp.:

50

Initial conc. measured:

0.4 mg/L

Duration:

0 h

pH:

7

Temp.:

50

Initial conc. measured:

0.421 mg/L

Duration:

0 h

pH:

9

Temp.:

50

Initial conc. measured:

0.407 mg/L

Duration:

0 h

pH:

9

Temp.:

50

Initial conc. measured:

0.349 mg/L

Number of replicates:

2 per pH and per sampling date

Positive controls:

not specified

Negative controls:

not specified

Statistical methods:

no

Preliminary study:

Preliminary Test/Tier 1: Sample solutions at pH 4, 7 and 9 were maintained at 50.0 ± 0.5 °C for a period of 5 days.
Test Tier 2: Results from the Preliminary Test/Tier 1 showed it was not necessary to undertake further testing at pH 4, 7 and 9.

Transformation products:

not specified

% Recovery:

99.6

St. dev.:

2

pH:

4

Temp.:

50 °C

Duration:

24 h

% Recovery:

98.2

St. dev.:

0.4

pH:

4

Temp.:

50 °C

Duration:

120 h

% Recovery:

98

St. dev.:

0.2

pH:

7

Temp.:

50 °C

Duration:

24 h

% Recovery:

92.3

St. dev.:

3.2

pH:

7

Temp.:

50 °C

Duration:

120 h

% Recovery:

104.5

St. dev.:

2.1

pH:

9

Temp.:

50 °C

Duration:

24 h

% Recovery:

102

St. dev.:

2.8

pH:

9

Temp.:

50 °C

Duration:

120 h

pH:

4

Temp.:

50 °C

DT50:

> 1 yr

Type:

not specified

pH:

7

Temp.:

50 °C

DT50:

> 1 yr

Type:

not specified

pH:

9

Temp.:

50 °C

DT50:

> 1 yr

Type:

not specified

Details on results:

TEST CONDITIONS
- pH, sterility, temperature, and other experimental conditions maintained throughout the study: yes
- Anomalies or problems encountered (if yes): no

MAJOR TRANSFORMATION PRODUCTS: not the purpose of the study

MINOR TRANSFORMATION PRODUCTS: not the purpose of the study

Table 1 Mean recovery of the test item in different pH buffer solutions (recalculated)

pH	Time (Hours)	Concentration (g/L) % of initial
		A	B	mean	SD
4	24	98.2	101	99.6	2.0
4	120	98.4	97.9	98.15	0.4
7	24	98.1	97.8	97.95	0.2
7	120	94.6	90.1	92.35	3.2
9	24	106	103	104.5	2.1
9	120	100	104	102	2.8

 

Validity criteria fulfilled:

yes

Conclusions:

Methylphosphonic acid 70 % was found to be hydrolytically stable with estimated half-life at 25 °C >1 year at pH 4, 7 and 9.

Executive summary:

In a valid, reliable and conclusive study, the hydrolysis behaviour of methylphosphonic acid 70 % has been determined. Assessment of hydrolytic stability was carried out using a procedure designed to be compatible with Method 111 of the OECD Guidelines for Testing of Chemicals, 13 April 2004. The results are summarized below:

pH 4: estimated half-life at 25 °C >1 year

pH 7: estimated half-life at 25 °C >1 year

pH 9: estimated half-life at 25 °C >1 year

Description of key information

In a valid, reliable and conclusive study, the hydrolysis behaviour of methylphosphonic acid 70 % has been determined. Assessment of hydrolytic stability was carried out using a procedure designed to be compatible with Method 111 of the OECD Guidelines for Testing of Chemicals. The results are summarized below:

pH 4: estimated half-life at 25 °C >1 year

pH 7: estimated half-life at 25 °C >1 year

pH 9: estimated half-life at 25 °C >1 year

Key value for chemical safety assessment

Half-life for hydrolysis:

1 yr

at the temperature of:

25 °C