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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:
20.11.2012 - 5.2.2013
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
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
- Sample storage conditions before analysis: At the required sampling times, a portion of sample solution was transferred into a vial and this sample was immediately analysed by HPLC. The concentration of MeOH was kept at < 1 % (v/v).
Buffers:
- pH: 4
Composition of buffer: 10.2 g of potassium hydrogen phthalate was weighed into a 1000 mL volumetric flask and dissolved in 250 mL of deionised water. 4 mL of 0.1M NaOH was then added and the volumetric flask was filled to volume with deionised water.

- pH: 7
Composition of buffer: 6.8 g of KH2PO4 was weighed into a 1000 mL volumetric flask and dissolved in 250 mL of deionised water. 296 mL of 0.1 M NaOH was then added and the volumetric flask was filled to volume with deionised water.

- pH: 9
Composition of buffer: 3.1 g of H3BO3 and 3.7 g of KCl were together weighed into a 1000 mL volumetric flask and dissolved in 250 mL of deionised water. 213 mL of 0.1M NaOH was then added and the volumetric flask was filled to volume with deionised water.
Details on test conditions:
TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: 100 mL volumetric flasks were used. 1 mL of calibration stock solution was pipetted into each. Each volumetric flask (in duplicate) was filled up to volume with an appropriate buffered solution of given pH. During the experimental part of hydrolysis, the volumetric flasks were placed in the thermostatic bath kept at a certain temperature.
- Sterilisation method: All prepared buffer solutions, glassware and reagent grade water were sterilised in an autoclave (121 °C, 90 minutes) and purged by nitrogen.
- Measures taken to avoid photolytic effects: The sample solutions in volumetric flasks were wrapped in aluminium foil
- Measures to exclude oxygen: Prior to preparation of a sample solution, each buffered solution was bubbled with nitrogen for at least 5 minutes. Flasks were tightly closed with a stopper.
- Is there any indication of the test material adsorbing to the walls of the test apparatus: Yes

TEST MEDIUM
- Kind and purity of water: deionized water

CALIBRATION STOCK SOLUTION
Approximately 30 mg of the test substance was weighed into a 100 mL volumetric flask, dissolved in and diluted to volume with MeOH (calibration stock solution, CSS). This stock solution was diluted with MeOH to three lower concentrations of calibration solutions (CS) as follows:
- CS-1: 1 mL CSS/50 mL MeOH, nominal concentration of 6 mg/L
- CS-2: 1 mL CSS/100 mL MeOH, nominal concentration of 3 mg/L
- CS-3: 1 mL CS-2/25 mL MeOH, nominal concentration of 0.12 mg/L
Duration:
5 d
pH:
4
Temp.:
50 °C
Initial conc. measured:
2.7 mg/L
Remarks:
Tier 1
Duration:
5 d
pH:
7
Temp.:
50 °C
Initial conc. measured:
2.74 mg/L
Remarks:
Tier 1
Duration:
5 d
pH:
9
Temp.:
50 °C
Initial conc. measured:
2.73 mg/L
Remarks:
Tier 1
Duration:
18 d
pH:
4
Temp.:
22 °C
Initial conc. measured:
2.61 - 2.63 mg/L
Remarks:
Tier 2
Duration:
18 d
pH:
7
Temp.:
22 °C
Initial conc. measured:
2.52 - 2.6 mg/L
Remarks:
Tier 2
Duration:
32 d
pH:
9
Temp.:
22 °C
Initial conc. measured:
2.55 - 2.6 mg/L
Remarks:
Tier 2
Duration:
12 d
pH:
4
Temp.:
50 °C
Initial conc. measured:
2.67 - 2.7 mg/L
Remarks:
Tier 2
Duration:
30 d
pH:
7
Temp.:
50 °C
Initial conc. measured:
2.73 - 2.74 mg/L
Remarks:
Tier 2
Duration:
30 d
pH:
9
Temp.:
50 °C
Initial conc. measured:
2.72 - 2.73 mg/L
Remarks:
Tier 2
Duration:
5 d
pH:
4
Temp.:
60 °C
Initial conc. measured:
2.6 - 2.63 mg/L
Remarks:
Tier 2
Duration:
18 d
pH:
7
Temp.:
60 °C
Initial conc. measured:
2.56 - 2.61 mg/L
Remarks:
Tier 2
Duration:
21 d
pH:
9
Temp.:
60 °C
Initial conc. measured:
2.59 - 2.62 mg/L
Remarks:
Tier 2
Number of replicates:
2 replicates per pH value per test
Preliminary study:
During the preliminary test (Tier 1) a decrease of more than about 10 % of the test substance concentration was observed. Therefore the test substance was considered to be hydrolytically unstable and Tier 2 was performed.
Transformation products:
no
Details on hydrolysis and appearance of transformation product(s):
In all experiments, there was no a significant signal of any possible hydrolytic product of the test substance. No degradation products were detected in all of tested buffered solutions.
Key result
Remarks on result:
other: Precipitation of the test substance and its subsequent adherence to glass affected the obtained results. Therefore the decrease of the test substance during the whole testing procedure was not caused by hydrolysis.
Details on results:
HYDROLYSIS OF UNSTABLE SUBSTANCE (TIER 2)
Different concentrations of the test substance from the parallel tests in the same buffered solution were obtained. That situation was the same for each used buffered solution and temperature during the whole Tier 2. At the end of Tier 2, precipitation of the test substance was observed in all of the tested buffered solutions. The precipitated test substance adhered to glass. Precipitation of the test substance and its subsequent adherence to glass affected the obtained results.
Therefore the decrease of the test substance during the whole testing procedure was not caused by hydrolysis. No degradation products were detected in all of tested buffered solutions.

IDENTIFICATION OF HYDROLYSIS PRODUCTS (TIER 3)
In all experiments, there was no significant signal of any possible hydrolytic product of the test substance. No degradation products were detected in all of tested buffered solutions.
Validity criteria fulfilled:
yes
Conclusions:
Under the conditions of this study, the test substance is considered to be hydrolytically stable.
Executive summary:

The potential of the test substance to undergo hydrolysis was investigated in accordance with Method C.7 – Degradation – Abiotic Degradation: Hydrolysis as a Function of pH, Council regulation (EC) No 440/2008, Published in OJ No L 142/518 May 2008.

A preliminary test (Tier 1) was performed at 50 ± 0.5 °C and pH 4.0, 7.0, and 9.0. During the preliminary test a decrease of more than about 10 % of the test substance concentration was observed. Therefore the test substance was considered to be hydrolytically unstable and Tier 2 was performed.

Tier 2 was carried out at 22, 50 and 60 °C and buffered solution with a nominal value of pH 4, 7 and 9. For Tier 3, any major hydrolysis products, at least those representing > 10 % of the applied dose, are to be identified by appropriate analytical methods.

At the end of Tier 2, precipitation of the test substance was observed in all of the tested buffered solutions. The precipitated test substance adhered to glass. Analyses from Tier 3 confirmed the presence of no degradation products in all of the tested buffered solutions.

On the basis of these observations, the decrease of the test substance during the whole testing procedure was not caused by hydrolysis. Therefore the test substance is considered to be hydrolytically stable. 

Description of key information

The test substance is considered to be hydrolytically stable. 

Key value for chemical safety assessment

Additional information

The potential of the test substance to undergo hydrolysis was investigated in accordance with Method C.7 – Degradation – Abiotic Degradation: Hydrolysis as a Function of pH, Council regulation (EC) No 440/2008, Published in OJ No L 142/518 May 2008.

A preliminary test (Tier 1) was performed at 50 ± 0.5 °C and pH 4.0, 7.0, and 9.0. During the preliminary test a decrease of more than about 10 % of the test substance concentration was observed. Therefore the test substance was considered to be hydrolytically unstable and Tier 2 was performed.

Tier 2 was carried out at 22, 50 and 60 °C and buffered solution with a nominal value of pH 4, 7 and 9. For Tier 3, any major hydrolysis products, at least those representing > 10 % of the applied dose, are to be identified by appropriate analytical methods.

At the end of Tier 2, precipitation of the test substance was observed in all of the tested buffered solutions. The precipitated test substance adhered to glass. Analyses from Tier 3 confirmed the presence of no degradation products in all of the tested buffered solutions.

On the basis of these observations, the decrease of the test substance during the whole testing procedure was not caused by hydrolysis. Therefore the test substance is considered to be hydrolytically stable.