1,1,2,2,3,3,4-heptafluorocyclopentane

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From 1997-06-24 to 1997-12-11

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

Specific details on test material used for the study:

Batch No.: 9705-1A
Purity: >97%

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

At each sampling time point, duplicate vials were removed, cooled and then extracted with three portions (5 mL) of ethyl acetate. The combined extracts were diluted to volume (20 mL) with ethyl acetate, dried over anhydrous sodium sulphate and analysed by gas chromatogrpahy.

Buffers:

- pH 4.0: Disodium hydrogen orthophosphate dodecahydrate (13.8 g) and citic acid monohydrate (6.46 g) were dissolved in purified water (950 mL) and the pH was adjusted to 4.0±0.05 with 1M hydrochloric acid. The volume was adjusted to 1000 mL with purified water. Measured pH = 4.00
- pH 7.0: Potassium dihydrogen orthophosphate (3.4 g) was dissolved in purified water (900 mL), 1M sodium hydroxide (15 mL) was added and the pH was adjusted to 7.0 ±0.05 with 1M hydrochloric acid. The volume was adjusted to 1000 mL with purified water. Measured pH = 7.03
- pH 9.0: Disodium tetraborate decahydrate (16.6 g) and potassium dihydrogen orthophosphate (1.80 g) were dissolved in purified water (900 mL) and the pH was adjusted to 9.0±0.05 with 1M hydrochloric acid. The volume was adjusted to 1000 mL with purified water. Measured pH = 9.05

Details on test conditions:

- Preliminary Investigation:
liquots (10 mL) of each buffer solution were measured into Wheaton vials, 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 (50 μL) of a stock solution (69.1 g/L) of test item in ethyl acetate to give a nominal concentration of approximately 350 mg/L. The bottles were transferred back to the oven and held in the dark until sampling was required. Sampling was performed after a short incubation period (approximately 10 minutes), 2.4, 72, 96 and 120 hours.
A rapid decline in test item concentration was seen at pH 9, consequently the experiment was repeated using sampling times of 0, 1, 2, 3.5, 5 and 6.5 hours. On this occasion the buffer solutions were spiked with a stock solution of test item in tetrahydrofuran in order to verify that the solvent did not affect the hydrolysis reaction.
- Definitive Study:
Aliquots (10 mL) of each buffer solution were measured into Wheaton vials (10 mL), purged with nitrogen and the vials sealed. Vials containing pH 7 buffer solution were placed in thermostatically controlled ovens at 50°C, 60°C and 70°C whilst those containing pH 9 buffer were placed in a water bath at 25°C.
When the buffer solutions had equilibrated at the temperature of the ovens, they were fortified with aliquots (50 μL) of a stock solution (65 g/L) of test item in tetrahydrofuran to give nominal concentrations of 325 mg/L. The bottles were transferred to the ovens and held in the dark until sampling was required. The ovens were monitored during the period of the test to ensure that the correct temperature was maintained.

Duration:

168 h

pH:

7

Temp.:

50 °C

Initial conc. measured:

320 mg/L

Duration:

78 h

pH:

7

Temp.:

60 °C

Initial conc. measured:

331 mg/L

Duration:

43 h

pH:

7

Temp.:

70 °C

Initial conc. measured:

325 mg/L

Duration:

216 h

pH:

9

Temp.:

25 °C

Initial conc. measured:

321 mg/L

Number of replicates:

2

Positive controls:

no

Negative controls:

no

Preliminary study:

There was no significant change in the concentration of test item when incubated in pH 4 buffer solution at 50°C, however, at pH 7 and 9 there was a significant change in test item concentration. As the degree of degradation of test item in the latter two buffers was less than 50% after 2.4 hours and greater than 10% after 5 days (equivalent to an environmental half-life, te1/2, of between 1 day and 1 year) further study of the degradative behaviour of test item was necessary at pH 7 and 9.

Test performance:

There was no significant change in pH of the buffer solution with time.

Transformation products:

not measured

pH:

4

Temp.:

50 °C

Remarks on result:

hydrolytically stable based on preliminary test

pH:

7

Temp.:

25 °C

Hydrolysis rate constant:

0 h-1

DT50:

105 d

Type:

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

pH:

9

Temp.:

25 °C

Hydrolysis rate constant:

0.005 h-1

DT50:

5.5 d

Type:

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

Validity criteria fulfilled:

not specified

Conclusions:

The preliminary investigation indicated that the test item was hydrolytically stable under acid conditions, however, the test substance hydrolysed under neutral and basic conditions.
The definitive tests allowed the half-lives at 25°C to be determined as 105 days at pH 7 and 5.5 days at pH 9

Executive summary:

The hydrolysis of test item as a function of pH was studied according to EEC guidelines.

The preliminary study showed that after 5 days at pH 4 and 50°C less than 10% hydrolysis had occurred, however at pH 7 and 9, greater than 10% hydrolysis had occurred after 5 days. This is equivalent to environmental half-lives (te1/2) of between 1 day and 1 year and necessitated proceeding to the next stage of testing (EEC Test 1) at pH 7 and 9.

No further testing was required at pH 4.

The hydrolysis reaction for test item at pH 7 and 9 was shown to follow pseudo-first order behavior, and the half-lives at 25°C to be determined as 105 days at pH 7 and 5.5 days at pH 9.

Description of key information

The hydrolysis of test item as a function of pH was studied according to EEC guidelines.

The preliminary study showed that after 5 days at pH 4 and 50°C less than 10% hydrolysis had occurred, however at pH 7 and 9, greater than 10% hydrolysis had occurred after 5 days. This is equivalent to environmental half-lives (te1/2) of between 1 day and 1 year and necessitated proceeding to the next stage of testing (EEC Test 1) at pH 7 and 9.

No further testing was required at pH 4.

The hydrolysis reaction for test item at pH 7 and 9 was shown to follow pseudo-first order behavior, and the half-lives at 25°C to be determined as 105 days at pH 7 and 5.5 days at pH 9.

Key value for chemical safety assessment

Half-life for hydrolysis:

105 d

at the temperature of:

25 °C

Additional information

The half-lives at 25°C to be determined as 105 days at pH 7 and 5.5 days at pH 9.