3,3,5,7,7-pentamethyl-1,2,4-trioxepane

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

The method is validated periodically using acetylsalicyclic acid.

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

Clear colourless liquid, purity 96.5%.

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

The test solutions at pH 4, pH 7 and pH 9 were placed in a thermostatically controlled water bath set at 50 oC in the dark. The concentration of the test substance was determined immediately after preparation (t=0), after 2.4 hours and after 5 days of incubation. At each sampling point, a 2 ml sample was taken for pretreatment and analysis.

The samples taken at t > 0 were cooled to room temperature with running tap-water immediately after sampling. Thereafter, each sample was diluted with Milli-Q water to obtain concentrations within the calibration range and analysed.

On the first day of each test, blank buffer solutions were diluted with Milli-Q water by the same factor as the corresponding test solutions.

Buffers:

A sterile 0.05 M acetate buffer pH 4: sodium acetate/acetic acid/Milli-Q water.
A sterile 0.05 M phosphate buffer pH 7: potassium dihydrogen phosphate/sodium hydroxide/Milli-Q water.
A sterile 0.05 M borate buffer pH 9: boric acid/potassium chloride/sodium hydroxide/Milli-Q water.

83mg pentamethyl-trioxepane is added to 50ml buffer pH 4, 7 or 9. Solutions were filter-sterilized through a 0.2 μm filter. pH values were determined at the beginning and the end of the tests.

Details on test conditions:

Preliminary test pH 4, 7 and 9: at 49.9 °C ± 0.2 up to 5 days. Higher tier test pH 4: conducted until 90% hydrolysis was observed, at 39.4 °C ± 0.1 up to 31 hours and 50 °C ± 0.1 for 23 hours.

Duration:

5 d

pH:

4

Temp.:

49.9 °C

Initial conc. measured:

1 503 mg/L

Remarks:

Preliminary test

Duration:

5 d

pH:

7

Temp.:

49.9 °C

Initial conc. measured:

1 494 mg/L

Remarks:

Preliminary test

Duration:

5 d

pH:

9

Temp.:

49.9 °C

Initial conc. measured:

1 539 mg/L

Remarks:

Preliminary test

Duration:

31 h

pH:

4

Temp.:

39.4 °C

Initial conc. measured:

1 485 mg/L

Remarks:

Higher tier test

Duration:

24.5 h

pH:

4

Temp.:

39.4 °C

Initial conc. measured:

1 609 mg/L

Remarks:

Higher tier test

Duration:

23 h

pH:

4

Temp.:

50 °C

Initial conc. measured:

1 478 mg/L

Remarks:

Higher tier test

Number of replicates:

duplicate at 39.4 oC pH 4 (higher tier test)

Positive controls:

no

Negative controls:

no

Preliminary study:

Preliminary test measured values (mg/L) after 5 days: pH 4, n.d.; pH 7, 1375; pH 9, 1500.
Preliminary test degradation % after 5 days: pH 4, 100%; pH 7, 8%; pH 4, 2%. Temperature 49.9 °C ± 0.2.

Test performance:

Higher tier test measured values (mg/L) pH 4: after 23 hours 237 (49.9 °C ± 0.2), after 31 hours 716 (39.4°C ± 0.1) and the duplicate after 24.5 hours 909
Higher tier test degradation % pH 4: after 23 hours at 49.9 °C ± 0.2 16% after 31 hours at 39.4°C ± 0.1 48% and the duplicate after 24.5 hours 57%.

Transformation products:

no

Details on hydrolysis and appearance of transformation product(s):

Half-life at pH 7 and pH 9 > 1 year at 25 °C and at pH 4 172 hours at 25 °C.
At pH 7 and pH 9, a decrease in concentration <10% was observed after 5 days. Therefore no further testing is required. The reactions at pH 4 were considered to be pseudo-first order hence a half life could be estimated after performing the higher tier test.

% Recovery:

80

pH:

4

Temp.:

49.9 °C

Duration:

2.4 h

Remarks on result:

other: Preliminary test

% Recovery:

0

pH:

4

Temp.:

49.9 °C

Duration:

5 d

Remarks on result:

other: Preliminary test

% Recovery:

94

pH:

7

Temp.:

49.9 °C

Duration:

2.4 h

Remarks on result:

hydrolytically stable based on preliminary test

% Recovery:

92

pH:

7

Temp.:

49.9 °C

Duration:

5 d

Remarks on result:

hydrolytically stable based on preliminary test

% Recovery:

96

pH:

9

Temp.:

49.9 °C

Duration:

2.4 h

Remarks on result:

hydrolytically stable based on preliminary test

% Recovery:

98

pH:

9

Temp.:

49.9 °C

Duration:

5 d

Remarks on result:

hydrolytically stable based on preliminary test

Key result

pH:

9

Temp.:

25 °C

DT50:

> 1 yr

Type:

other: stable

Remarks on result:

hydrolytically stable based on preliminary test

Key result

pH:

7

Temp.:

25 °C

DT50:

> 1 yr

Type:

other: stable

Remarks on result:

hydrolytically stable based on preliminary test

Key result

pH:

4

Temp.:

50 °C

Hydrolysis rate constant:

ca. 0.078 h-1

DT50:

8.92 h

Type:

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

Key result

pH:

4

Temp.:

39.4 °C

Hydrolysis rate constant:

ca. 0.235 h-1

DT50:

29.5 h

Type:

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

Key result

pH:

4

Temp.:

25 °C

Hydrolysis rate constant:

0.004 h-1

DT50:

172 h

Type:

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

Remarks on result:

other: rate constant estimated using Arrhenius equation

Validity criteria fulfilled:

yes

Conclusions:

Pentamethyl-trioxepane is hydrolytically stable (half-life > 1 year at 25 °C) in aqueous solutions buffered at pH 7 and pH 9. The half-life of pentamethyl-trioxepane is 172 hours in aqueous solutions buffered at pH 4 at 25 °C.

Executive summary:

Pentamethyl-trioxepane is hydrolytically stable (half-life > 1 year at 25 °C) in aqueous solutions buffered at pH 7 and pH 9. The half-life of pentamethyl-trioxepane is 172 hours in aqueous solutions buffered at pH 4 at 25 °C.

Description of key information

Pentamethyl-trioxepane is hydrolytically stable (half-life > 1 year at 25 °C) in aqueous solutions buffered at pH 7 and pH 9. The half-life of pentamethyl-trioxepane is 172 hours in aqueous solutions buffered at pH 4 at 25 °C.