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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
Study period:
2012-04-27 to 2012-07-06
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Version / remarks:
(2004)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)
Version / remarks:
(2008)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
In the preliminary test, samples were taken at test start (0 h) and at test end (120 h).
For definitive testing, samples were taken at test start and at a minimum of 8 spaced points, normally between 10 and 90 % of hydrolysis, at each test temperature.
All samples were analysed immediately (max. 60 min for preparation and analyses) via LC-MS/MS.
Buffers:
pH 4: 45 mL of 0.1 mol/L NaOH were mixed with 250 mL 0.1 mol/L monopotassium citrate and diluted to 500 mL with double distilled water.
pH 7: 148.15 mL of 0.1 mol/L NaOH were mixed with 250 mL 0.1 mol/L KH2PO4 and diluted to 500 mL with double distilled water.
pH 9: 106.5 mL of 0.1 mol/L NaOH were mixed with 2500 mL 0.1 mol/L H3BO3 in 0.1 mol/L KCl and diluted to 500 mL with double distilled water.

Buffers were prepared from chemicals with analytical grade or better quality. Buffers were purged with nitrogen for 5 min. Then the pH was checked to a precision of at least 0.1 at the required temperature, adjusted if necessary and sterilised by filtration through 0.22 µm.
Details on test conditions:
Stock solution: 100 mg/L acetonitrile, diluted to 1500 µg/L
Co-solvent: Acetonitrile, 10 % (v/v)
Test concentration: 150 µg/L buffer solution
Control: Sterile buffer solutions (pH value 4, 7 and 9)
Test vessels: Sterile amber HPLC vials, volume: 4 mL
Test volume: 2 mL
Temperatures
- Preliminary test: 50°C ± 0.5 °C
- Definitive test: 20, 30 and 50°C ± 0.5 °C
The bath temperature was checked automatically once an hour.
Sterility: Checked by colony forming units (CFU)-determination with Water Plate Count Agar (additional samples).
Duration:
598 h
pH:
4
Temp.:
20 °C
Initial conc. measured:
141 µg/L
Duration:
264 h
pH:
4
Temp.:
30 °C
Initial conc. measured:
141 µg/L
Duration:
44.1 h
pH:
4
Temp.:
50 °C
Initial conc. measured:
141 µg/L
Duration:
692 h
pH:
7
Temp.:
20 °C
Initial conc. measured:
137 µg/L
Duration:
691 h
pH:
7
Temp.:
30 °C
Initial conc. measured:
137 µg/L
Duration:
335 h
pH:
7
Temp.:
50 °C
Initial conc. measured:
137 µg/L
Duration:
691 h
pH:
9
Temp.:
20 °C
Initial conc. measured:
133 µg/L
Duration:
690 h
pH:
9
Temp.:
30 °C
Initial conc. measured:
133 µg/L
Duration:
261 h
pH:
9
Temp.:
50 °C
Initial conc. measured:
133 µg/L
Number of replicates:
Duplicates
Positive controls:
no
Negative controls:
yes
Remarks:
Sterile buffer solutions (pH 4, 7 and 9) sampled at test start and test end.
Statistical methods:
average of two determinations
Preliminary study:
In the preliminary test more than 10 % of the test item was hydrolysed after 120 hours at pH 4, 7 and 9:
pH 4: 92.1 %; pH 7: 56.9 %; pH 9: 59.4%
Test performance:
- The pH of the test solution did not differ for more than ± 0.1 from the nominal value at test temperature.
- The test temperatures should have been within ± 0.5 °C of the nominal temperature. At target temperature 50 °C the temperature was below the intended temperature range for 4 x 1 hour of the total incubation time. Compared to the total incubation time this short term deviation could be regarded as negligible and having no significant influence on the study results.
Transformation products:
not measured
pH:
4
Temp.:
20 °C
Hydrolysis rate constant:
0 s-1
DT50:
187 h
Type:
(pseudo-)first order (= half-life)
pH:
4
Temp.:
30 °C
Hydrolysis rate constant:
0 s-1
DT50:
79.4 h
Type:
(pseudo-)first order (= half-life)
pH:
4
Temp.:
50 °C
Hydrolysis rate constant:
0 s-1
DT50:
12.8 h
Type:
(pseudo-)first order (= half-life)
Key result
pH:
7
Temp.:
20 °C
Hydrolysis rate constant:
0 s-1
DT50:
666 h
Type:
(pseudo-)first order (= half-life)
pH:
7
Temp.:
30 °C
Hydrolysis rate constant:
0 s-1
DT50:
625 h
Type:
(pseudo-)first order (= half-life)
pH:
7
Temp.:
50 °C
Hydrolysis rate constant:
0 s-1
DT50:
114 h
Type:
(pseudo-)first order (= half-life)
pH:
9
Temp.:
20 °C
Hydrolysis rate constant:
0 s-1
DT50:
1 385 h
Type:
(pseudo-)first order (= half-life)
pH:
9
Temp.:
30 °C
Hydrolysis rate constant:
0 s-1
DT50:
630 h
Type:
(pseudo-)first order (= half-life)
pH:
9
Temp.:
50 °C
Hydrolysis rate constant:
0 s-1
DT50:
87.1 h
Type:
(pseudo-)first order (= half-life)
Details on results:
Concentrations at test end (µg/L; for initial concentrations and test duration see above)
pH 4, 20 °C: 13.5 (11th sample)
pH 4, 30 °C: 9.32 (10th sample)
pH 4, 50 °C: 8.36 (9th sample)
pH 7, 20 °C: 85.8 (11th sample)
pH 7, 30 °C: 46.0 (11th sample)
pH 7, 50 °C: 17.7 (11th sample)
pH 9, 20 °C: 81.0 (11th sample)
pH 9, 30 °C: 46.8 (11th sample)
pH 9, 50 °C: 15.2 (10th sample)

Reaction Rate Constants and Half-Lives

 

 

pH 4

pH 7

pH 9

 


20 °C


30 °C


50 °C


20 °C


30 °C


50 °C


20 °C


30 °C


50 °C

Reaction rate constantkobs
[1/s]

1.03 x
10-6

2.43 x
10-6

1.51 x
10-5

2.89 x
10-7

3.08 x
10-7

1.69 x
10-6

1.39 x
10-7

3.06 x
10-7

2.21 x
10-6

Half-lifeT½[h]

187

79.4

12.8

666

625

114

1385

630

87.1

Half-lifeT½[d]

7.79

3.31

0.533

27.8

26.0

4.75

57.7

26.3

3.63

Conclusions:
The hydrolysis of Cyclohexane, 5-isocyanato-1-(isocyanatomethyl)-1,3,3-trimethyl-, homopolymer, acetone oxime-blocked was tested according to OECD TG 111 (2004) and EU Method C.7 (2008). In the preliminary test, more than 10% of the test substance was observed to hydrolyse at 50 °C at pH 4,7 and 9 after 120 hours. In the main test low rates of hydrolysis were determined for all pH values at temperatures of 20 and 30 °C and moderate rates at 50 °C. The half-lives derived for 20 °C are 187 h (pH 4), 666 h (pH 7) and 1385 h (pH 9).
Executive summary:

The hydrolysis of Cyclohexane, 5-isocyanato-1-(isocyanatomethyl)-1,3,3-trimethyl-, homopolymer, acetone oxime-blocked was tested according to OECD TG 111 (2004) and EU Method C.7 (2008). In the preliminary test, more than 10% of the test substance was observed to hydrolyse at 50 °C at pH 4,7 and 9 after 120 hours. In the main test low rates of hydrolysis were determined for all pH values at temperatures of 20 and 30 °C and moderate rates at 50 °C. The half-lives derived for 20 °C are 187 h (pH 4), 666 h (pH 7) and 1385 h (pH 9).

Description of key information

The hydrolysis of Cyclohexane, 5-isocyanato-1-(isocyanatomethyl)-1,3,3-trimethyl-, homopolymer, acetone oxime-blocked was tested according to OECD TG 111 (2004) and EU Method C.7 (2008). In the preliminary test, more than 10% of the test substance was observed to hydrolyse at 50 °C at pH 4,7 and 9 after 120 hours. In the main test low rates of hydrolysis were determined for all pH values at temperatures of 20 and 30 °C and moderate rates at 50 °C. The half-lives derived for 20 °C are 187 h (pH 4), 666 h (pH 7) and 1385 h (pH 9).

Key value for chemical safety assessment

Half-life for hydrolysis:
666 h
at the temperature of:
20 °C

Additional information