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Hydrolysis

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Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2013-12-18 to 2013-12-18
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
test procedure in accordance with generally accepted scientific standards and described in sufficient detail
Remarks:
No GLP and no guideline study, but detailed and well-described analytical method available. The study was conducted in equivalent conditions to good laboratory praxis.
Qualifier:
no guideline followed
Principles of method if other than guideline:
The test substance was investigated in terms of its relative hydrolysis rates as a function of the pH value (4, 6, 7 and 9) by means of flow injection mass spectrometry (FIMS). In this regard short- and long-term measurements were performed.
GLP compliance:
yes
Remarks:
The study was conducted with equivalence to good laboratory praxis conditions.
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
- Common name: Sika Hardener AI
- Chemical formula: C24H42N2O4
- Mass: 422.31446 g/mol
- Batch I1300718-13565-AKM (SW404/05)
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
- Short-term measurements:
The test substance was dissolved in methanol (20 µg/mL). The sample solution was injected by a syringe pump (10 µL/min) through a T-piece into an aqueous carrier flow. The T-piece was located at a given distance to the entrance of the mass spectrometer.
The hydrolysis conditions for pH 4 were varied as described:
Variation of the injection distance (40, 72 and 165 cm) and the flow rate:
a) At a flow rate of 400 µL/min reaction times of 0.8, 1.4 and 3.1 seconds were estimated.
b) At a flow rate of 200 µL/min reaction times of 1.6, 2.8 and 6.2 seconds were estimated.

For the hydrolysis experiments at pH ≈6, ultra-pure water was used.
For the hydrolysis experiments at pH 7 and 9, the buffer stock solutions were diluted with water (10:90). The injection distance was 40 cm and the carrier flow rate was set to 400 µL/min. Esti-mated hydrolysis time: 0.8 seconds.

- Long-term measurements
For hydrolysis experiments at pH 4, 2 mL of sample solution (100 µg/mL, dissolved in MeOH) were added to 3 mL MeOH, 2 mL of buffer stock solution pH 4 and finally to 3 mL of water. The solution was thoroughly mixed. At a constant carrier flow rate of 400 µL/min (water / 1 mM NH4HCOO in MeOH = 30:70), the sample solution was injected by a syringe pump (10 µL/min) directly into the mass spectrometer. Injections were performed 2 min after mixing with the aqueous solution.
For hydrolysis experiments at pH≈ 6, 2 mL of sample solution (100 µg/mL, dissolved in MeOH) were added to 3 mL MeOH and 5 mL of ultrapure water. The injection was performed 2 min after mixing with the aqueous solution.
For hydrolysis experiments at pH 7 and 9, 2 mL of sample solution (100 µg/mL, dissolved in MeOH) was added to 3 mL MeOH and diluted buffer stock solution (10:90). The solution was thoroughly mixed. At a carrier flow rate of 400 µL/min (water / 1 mM NH4HCOO in MeOH = 30:70), the sample solution was injected by a syringe pump (10 µL/min) directly into the mass spectrometer. Injections were performed 2 min (pH 7); 2, 20 and 90 min (pH 9) after mixing with the aqueous solution.
Buffers:
Composition of the buffer stock solutions:
- pH 4: 5.7 g Ammonium formate and 1.885 mL (0.1 M) of formic acid were dissolved and di-luted to 500 mL with ultra-pure water.
- pH ≈6: ultra-pure water
- pH 7: 10.9 g Diammonium hydrogenphosphate and 1 mL formic acid (0.05 M) were dis-solved and diluted to 500 mL with ultra-pure water.
- pH 9: 3.2 g Ammonium formate (0.1 M) and 2.0 mL ammonia solution (25 %) were dissolved and diluted with ultra-pure water.
Details on test conditions:
TEST MEDIUM
- The pH of each buffer solution was checked with a calibrated pH meter.
Duration:
0.013 min
pH:
4
Temp.:
25 °C
Initial conc. measured:
20 other: µg/mL
Duration:
0.023 min
pH:
4
Temp.:
25 °C
Initial conc. measured:
20 other: µg/mL
Duration:
0.051 min
pH:
4
Temp.:
25 °C
Initial conc. measured:
20 other: µg/mL
Duration:
0.026 min
pH:
4
Temp.:
25 °C
Initial conc. measured:
20 other: µg/mL
Duration:
0.047 min
pH:
4
Temp.:
25 °C
Initial conc. measured:
20 other: µg/mL
Duration:
0.103 min
pH:
4
Temp.:
25 °C
Initial conc. measured:
20 other: µg/mL
Duration:
0.013 min
pH:
6
Temp.:
25 °C
Initial conc. measured:
20 other: µg/mL
Duration:
0.013 min
pH:
7
Temp.:
25 °C
Initial conc. measured:
20 other: µg/mL
Duration:
0.013 min
pH:
9
Temp.:
25 °C
Initial conc. measured:
20 other: µg/mL
Number of replicates:
1 replicate
Positive controls:
not specified
Negative controls:
not specified
Transformation products:
yes
No.:
#1
No.:
#2
Key result
pH:
4
Temp.:
20 °C
DT50:
< 6.2 min
Key result
pH:
6
Temp.:
20 °C
DT50:
< 2 min
Key result
pH:
7
Temp.:
20 °C
DT50:
< 2 min
Key result
pH:
9
Temp.:
20 °C
DT50:
< 90 min
Details on results:
Based on the short term measurements (0.8 sec.), the hydrolysis was clearly visible at pH 4, at higher pH values only traces of the hydrolysis products were observed.
The test substance hydrolyzes at pH 4 within 3 to 4 seconds completely, at pH 6 and 7 within less than 2 minutes. At pH 9 the test substance hydrolyzes within less than 90 minutes.

Estimation of half-lives:
- FIMS data showed that at pH = 4 after 6.2 minutes no signals of the test substance could be detected. Thus the hydrolysis half-live at pH = 4 was considered to be < 6.2 minutes.
- FIMS data showed that at pH = 6 after 2 minutes only a weak signal of the test substance could be detected. Thus the hydrolysis half-live at pH = 6 was considered to be < 2 minutes.
- FIMS data showed that at pH = 7 after 2 minutes only a weak signal of the test substance could be detected. Thus the hydrolysis half-live at pH = 7 was considered to be < 2 minutes.
- FIMS data showed that at pH = 9 after 90 minutes no signal of the test substance could be detected. Thus the hydrolysis half-live at pH = 9 was considered to be < 90 minutes.


Transformation product #1:

- Chemical name: Isophorone diamine (IPDA)

- protonated form MH+: 171.18558, C10H23N2+

Transformation product #2:

- Common name: Aldehyde A

- protonated form MH+: 145.08592, C7H13O3+

Validity criteria fulfilled:
not specified
Conclusions:
The hydrolysis rate of the test substance at pH = 4, 6, 7 and 9 (at room temperature) was investigated using FIMS (Flow Injection Mass Spectrometry). Short- and long-term measurements show that the test substance hydrolyzed faster at pH 4, 6 and 7 than at pH 9. FIMS data showed that at pH = 7 after 2 minutes only a weak signal of the test substance could be detected. Thus the hydrolysis half-live at pH = 7 was considered to be < 2 minutes.
Executive summary:

The hydrolysis of the test substance pH = 4, 6, 7 and 9 (at room temperature) was investigated using FIMS (Flow Injection Mass Spectrometry). Short- and long-term measurements show that the test substance hydrolyzed faster at pH 4, 6, 7 than at pH 9 and that the hydrolysis reaction occured at pH 7 within a few minutes. The compounds isophorone diamine (protonated form, MH+ = 171.18558) and Aldehyde A (protonated form, MH+ = 145.08592) were formed during the hydrolysis reaction of the test item.

FIMS data showed that at pH = 4 after 6.2 minutes no signals of the test substance could be detected. Thus the hydrolysis half-live at pH = 4 was considered to be < 6.2 minutes. At pH = 6 and 7 after 2 minutes only a weak signal of the test substance could be detected. Thus the hydrolysis half-live at pH = 6 and 7 was considered to be < 2 minutes. At pH = 9 after 90 minutes no signal of the test substance could be detected. Thus the hydrolysis half-live at pH = 9 was considered to be < 90 minutes.

Description of key information

The hydrolysis rate of the test substance at pH = 4, 6, 7 and 9 (at room temperature) was investigated using FIMS (Flow Injection Mass Spectrometry). Short- and long-term measurements show that the test substance hydrolyzed faster at pH 4, 6 and 7 than at pH 9. FIMS data showed that at pH = 7 after 2 minutes only a weak signal of the test substance could be detected. Thus the hydrolysis half-live at pH = 7 was considered to be < 2 minutes. 

Key value for chemical safety assessment

Half-life for hydrolysis:
2 min
at the temperature of:
25 °C

Additional information

The hydrolysis of the test substance pH = 4, 6, 7 and 9 (at room temperature) was investigated using FIMS (Flow Injection Mass Spectrometry). Short- and long-term measurements show that the test substance hydrolyzed faster at pH 4, 6, 7 than at pH 9 and that the hydrolysis reaction occured at pH 7 within a few minutes. The compounds isophorone diamine (protonated form, MH+ = 171.18558) and Aldehyde A (protonated form, MH+ = 145.08592) were formed during the hydrolysis reaction of the test item.

FIMS data showed that at pH = 4 after 6.2 minutes no signals of the test substance could be detected. Thus the hydrolysis half-live at pH = 4 was considered to be < 6.2 minutes. At pH = 6 and 7 after 2 minutes only a weak signal of the test substance could be detected. Thus the hydrolysis half-live at pH = 6 and 7 was considered to be < 2 minutes. At pH = 9 after 90 minutes no signal of the test substance could be detected. Thus the hydrolysis half-live at pH = 9 was considered to be < 90 minutes. As key value for chemical risk assessment the half-life for hydrolysis was set to 2 minutes (worst case at pH 7).