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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:
EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: Probelte S.A., Manufacturer batch number: 7003, Probelte batch number: 312432
- Sort of product: Solid crystalline
- Expiration date of the lot/batch: Not specified
- Purity test date: 99.9% p/p

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Maintain at room temperature
- Stability under testing conditions
Radiolabelling:
yes
Analytical monitoring:
yes
Duration:
5 d
pH:
4
Temp.:
25 °C
Initial conc. measured:
0.271 g/L
Duration:
5 d
pH:
7
Temp.:
25 °C
Initial conc. measured:
0.271 g/L
Duration:
5 d
pH:
9
Temp.:
25 °C
Initial conc. measured:
0.271 g/L
Preliminary study:
Three samples were prepared to a concentration equal to half the saturation concentration (0.26-0.27 g/L) and dissolved in the buffered solutions at pH 4, 7 and 9. A known quantity of 8-HQ technical product has been weighed to contain 0.0265g in 100 ml the buffered solution. After these 3 samples are prepared, they are submitted at 50C for a period between 2,4hours and 5 days. Some aliquots are periodically taken and analyzed, quantifying the content of 8.HQ by HPLC.
Transformation products:
not specified
pH:
4
Temp.:
25 °C
Hydrolysis rate constant:
0.59 d-1
DT50:
> 1 yr
Type:
not specified
pH:
7
Temp.:
25 °C
Hydrolysis rate constant:
8.61 d-1
DT50:
> 1 yr
Type:
not specified
pH:
9
Temp.:
25 °C
Hydrolysis rate constant:
54.3 d-1
DT50:
> 1 yr
Type:
not specified
Validity criteria fulfilled:
yes
Conclusions:
The half-life for 8-HQ dissolved in buffered solution at pH 4, 7 and 9 is higher thatn 1 year in the environmentak relevant conditions (25 C)
Executive summary:

The stability of 8-hydroxyquinoline to hydrolysis at pH 4, 7 and 9 was tested on a preliminary study at 50ºC (García, A. 2004). The study was conducted according to the EEC C.7 guideline, "abiotic degradation: hydrolysis as a function of pH". The concentrations of test item were quantified via HPLC and external standards.

In the preliminary test, 8-HQ samples were dissolved in buffered solutions of different pH values, and the they were put at 50C with a lack of light to observe the pH and temperature effects of the active ingredient on hydrolysis. In this way, no hydrolysis of the active ingredient was observed in the sample at Ph 4, In the sample of pH 7, a hydrolysis lower than 10% was observed after 5 days at 50C with a lack of light. In the sample at Ph9, when sample was dissolved. In the sample at pH 9, when the sample was dissolved with the lack of light and presence of oxygen, a decreased of concentration was observed in the assay conditions of the preliminary test. Due to the decreased of the concentration that the active ingredient shows at a basic Ph, the preliminary test was carried out in conditions of nitrogen atmosphere, with a lack of light and at 50C, using two different buffered solutions at pH 9. Hydrolysis lower than 10% has been obtained in both cases under mentioned conditions after 5 days.

Description of key information

The stability of 8-hydroxyquinoline to hydrolysis at pH 4, 7 and 9 was tested on a preliminary study at 50ºC (García, A., 2004). The study was conducted according to the EEC C.7 guideline, "abiotic degradation: hydrolysis as a function of pH". The concentrations of test item were quantified via HPLC and external standards. The results indicate that 8-HQ was stable to hydrolysis at pH 4 and 7 and 50ºC after 5 days (<10% degradation). At pH 9 it was also stable in the absence of oxygen (< 10% degradation). Hence, the half-life for 8-HQ dissolved in buffered solution at pH 4, 7 and 9 is higher thatn 1 year in the environmental relevant conditions (25 degrees Celsius).

Key value for chemical safety assessment

Half-life for hydrolysis:
1 yr
at the temperature of:
25 °C

Additional information