Phosphinic acid, P-[3-(acetyloxy)-3-cyanopropyl]-P-methyl-, butyl ester

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1995

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)

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

- Sampling intervals/times for pH measurements: At the end of each incubation time one flasks per buffer or unbuffered water and sampling time was removed from the water bath. The sample pH was measured and an aliquot was directly injected into the HPLC.

Buffers:

- pH: The pH values remained moderately constant during the entire experimental period irrespective of buffered or unbuffered system.
- Composition of buffer: The buffer solution (0.05 mol/l) was prepared by Analytisches Laboratorium, Hoechst AG, using de-ionised water.
pH 8: 6.8 g potassium dihydrogen phosphate were dissolved in 4800 mL of de-ionised water. This solution was adjusted with aqueous sodium hydroxide solution (1 mol/L) to pH 8.0 and was finally brought to a volume of 5000 mL with de-ionised water.

Details on test conditions:

TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: centrifugation tubes
- Sterilisation method:
glassware: two hours at 180 °C in a desiccator cabinet
buffer: boiling twice for 20 minutes within 24 hours
- Lighting: dark
- Closed system
- Is there any indication of the test material adsorbing to the walls of the test apparatus? no
TEST MEDIUM
- Volume used: 3 ml
- Kind and purity of water: sterile buffer or unbuffered water
- Preparation of test medium: approx. 130 - 150 mg Hoe 125869 were weighed into 50 ml volumetric flasks for the buffer and unbuffered water and filled up to the mark with the respective sterile buffer or unbuffered water.

Positive controls:

no

Negative controls:

no

Transformation products:

not specified

pH:

8

Temp.:

60 °C

Hydrolysis rate constant:

0.42 h-1

DT50:

0.07 d

St. dev.:

0.97

Type:

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

pH:

8

Temp.:

40 °C

Hydrolysis rate constant:

0.09 h-1

DT50:

0.33 d

St. dev.:

0.99

Type:

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

pH:

8

Temp.:

22 °C

Hydrolysis rate constant:

0.01 h-1

DT50:

2.22 d

St. dev.:

0.99

Type:

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

pH:

4.2

Temp.:

60 °C

DT50:

172 d

St. dev.:

0.8

Type:

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

Remarks on result:

other: Hydrolysis rate: 0.00017 h-1

Other kinetic parameters:

first order rate constant k = 0.01301 h-1
correlation coefficient r^2 = 0.98637

Details on results:

Under abiotic conditions the test substance appeared to be hydrolytically unstable in a buffer solution (pH 8, 0.05 mol/L) with hydrolytical half lives between 22°C and 60°C never exceeding 3 days.
However, at pH 4 (unbuffered water) turned out to be hydrolytically stable with a half life time of 172 days ( 25°C).
Due to an increase in the final mean concentration (occurrence of unknown products), a hydrolytic half life could not be calculated for higher temperatures (60°C).

Validity criteria fulfilled:

yes

Conclusions:

Under abiotic conditions the test item appeared to be hydrolytically unstable in a buffer solution (pH 8, 0.05 mol/L) with hydrolytical half lives between 22°C and 60°C never exceeding 3 days. However, at pH 4 (unbuffered water) turned out to be hydrolytically stable with a half life time of 172 days ( 25°C).
The test substance turned out to be hydrolytically stable with half life of approx. 1 70 days in unbuffered water (pH 4, 25°C), whereas with increasing temperatures (60°C ) the intermediate appeared to be hydrolytically less stable.

Description of key information

A hydrolysis study was performed with CAS 167004-78-6 according to the OECD Guideline 111 at temperatures between 22 and 60°C.

Under abiotic conditions the test item appeared to be hydrolytically unstable in a buffer solution (pH 8, 0.05 mol/L) with hydrolytical half lives between 22°C and 60°C never exceeding 3 days. However, at pH 4 (unbuffered water) turned out to be hydrolytically stable with a half life time of 172 days ( 25°C).
The test substance turned out to be hydrolytically stable with half life of approx. 170 days in unbuffered water (pH 4, 25°C), whereas with increasing temperatures (60°C ) the intermediate appeared to be hydrolytically less stable.

Key value for chemical safety assessment

Half-life for hydrolysis:

170 d

at the temperature of:

25 °C