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Environmental fate & pathways

Hydrolysis

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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.

Key value for chemical safety assessment

Additional information