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Environmental fate & pathways

Hydrolysis

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Administrative data

Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2004-06-07 - 2004-07-19
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2004
Report date:
2005

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Version / remarks:
12 May 1981.
GLP compliance:
yes (incl. QA statement)

Test material

Constituent 1
Chemical structure
Reference substance name:
Flucytosine
EC Number:
217-968-7
EC Name:
Flucytosine
Cas Number:
2022-85-7
Molecular formula:
C4H4FN3O
IUPAC Name:
flucytosine
Test material form:
solid: particulate/powder
Specific details on test material used for the study:
please refer to Test material information
Radiolabelling:
no

Study design

Analytical monitoring:
yes
Details on sampling:
- Sampling intervals for the parent/transformation products: 0 h, 2.4 h, 24 h, 120 h
- Sampling method: Aliquots of the sample solutions were taken from the flasks at various times and the pH of each solution recorded. The concentration of the sample solution was determined by high performance liquid chromatography (HPLC). Samples: Duplicate aliquots (A and B) of sample solution were diluted by a factor of 20 using methanol. Standards: Duplicate standard solutions of test material were prepared in methanol : relevant buffer solution at a nominal concentration of 50 mg/L.
- Sampling intervals/times for pH measurements: 0 h, 2.4 h, 24 h, 120 h
Buffers:
- pH: 4
- Type and final molarity of buffer:
- Composition of buffer: 50.0 mmol/L Potassium dihydrogen citrate, 9.0 mmol/l Sodium hydroxide

- pH: 7
- Type and final molarity of buffer:
- Composition of buffer: 7.5 mmol/L Disodium hydrogen orthophosphate (anhydrous), 5.0 mmol/L Potassium dihydrogen orthophosphate, 5.0 mmol/L Sodium chloride

- pH: 9
- Type and final molarity of buffer:
- Composition of buffer: 2.5 mmol/L Disodium tetraborate, 5.0 mmol/L Sodium chloride

The buffer solutions were filtered through a 0.2 µm membrane filter to ensure they were sterile before commencement of the test. Also these solutions were subjected to ultrasonication and degassing with nitrogen to minimise dissolved oxygen content.
Details on test conditions:
TEST SYSTEM
- Sterilisation method: The buffer solutions were filtered through a 0.2 µm membrane filter to ensure they were sterile before commencement of the test.
- Lighting: none
- Measures taken to avoid photolytic effects: The solutions were shielded from light whilst maintained at the test temperature.
- If no traps were used, is the test system closed/open: closed

OTHER TEST CONDITIONS
- Preparation of samples: Sample solutions were prepared in stoppered glass flasks at a nominal concentration of 1.0 g/L in the three buffer solutions.
- Preliminary test: Sample solutions at pH 4, 7 and 9 were maintained at 50.0 ± 0.5°C for a period of 5 days.

Positive controls:
not specified
Negative controls:
not specified
Statistical methods:
Calculation
Sample solution concentration
The mean peak area of each standard was corrected to a nominal concentration of 50 mg/L and the mean value taken.
The concentration of the sample solutions (g/L) was calculated using the following equation:
C spl = ( P spl / P std ) * C std * D * ( 1 / 1000)
where:
C spl = sample concentration (g/L)
P spl = mean peak area of sample solution
P std = mean peak area of standard solution, corrected to nominal standard concentration
C std = nominal standard concentration (50 mg/L)
D = sample dilution factor (20)

Results and discussion

Preliminary study:
At each pH, less than 10% hydrolysis occured after 5 days at 50°C, equivalent to a half-life greater than 1 year at 25°C.
Transformation products:
not specified
Total recovery of test substance (in %)open allclose all
% Recovery:
100
pH:
4
Temp.:
50 °C
Duration:
2.4 h
Remarks on result:
other: Temp: 50.0 ± 0.5ºC
% Recovery:
99.8
pH:
4
Temp.:
50 °C
Duration:
24 h
% Recovery:
99.1
pH:
4
Temp.:
50 °C
Duration:
120 h
% Recovery:
100
pH:
7
Temp.:
50 °C
Duration:
2.4 h
% Recovery:
100
pH:
7
Temp.:
50 °C
Duration:
24 h
% Recovery:
100
pH:
7
Temp.:
50 °C
Duration:
120 h
% Recovery:
99.8
pH:
9
Temp.:
50 °C
Duration:
2.4 h
% Recovery:
99.8
pH:
9
Temp.:
50 °C
Duration:
24 h
% Recovery:
101
pH:
9
Temp.:
50 °C
Duration:
120 h
Dissipation DT50 of parent compoundopen allclose all
Key result
pH:
4
Temp.:
50 °C
Remarks on result:
hydrolytically stable based on preliminary test
Key result
pH:
7
Temp.:
50 °C
Remarks on result:
hydrolytically stable based on preliminary test
Key result
pH:
9
Temp.:
50 °C
Remarks on result:
hydrolytically stable based on preliminary test

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Remarks:
The linearity of the detector response with respect to concentration was assessed over the nominal concentration range of 0 to 400 mg/l. This was satisfactory with a correlation coefficient of 1.000 being obtained.
Conclusions:
The estimated half-life at 25°C of the test material at pH 4, pH 7, and pH 9 is > 1 year.