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Hydrolysis

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Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
comparable to guideline study
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Deviations:
yes
Remarks:
test conducted before quideline was issued but if anything, more severe.
Principles of method if other than guideline:
The study did not exactly follow OECD 111 since it has been performed before the issue of the guideline. If anything the testing conditions are more severe than requested in the OECD 111 guideline.
Here:
1) 5 pH conditions have been investigated, namely: 1 M HCl solution, pH 3 citrate-phosphate buffer, pH 6 citrate-phosphate buffer, pH 9 citrate-phosphate buffer, 1 M NaOH solution.
2) 2 storage temperatures, namely 40°C and 100°C.
3) The samples were stored up to 20 days.
For comparison, the OECD guideline would request to perform the test at pH 4, pH 7 and pH9 at 50°C for one week.
GLP compliance:
not specified
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
- Sampling intervals for the parent/transformation products: 0, 20, 41, 61 days
- Sampling method: duplicate ampules for each series were removed from the climate room
- Sampling intervals/times for pH measurements: 0, 20, 41, 61 days
- Sample storage conditions before analysis: at -20°C
- Other observation, if any (e.g.: precipitation, color change etc.): none indicated
Buffers:
- pH: 5 and 7
- Type and final molarity of buffer: citrate-phosphate
- Composition of buffer: mixing appropriate volumes of 0.01 M citric acid and 0.02 M Na2HPO4 solutions

- pH: 9
- Type and final molarity of buffer: borax - hydrochloric acid
- Composition of buffer: mixing appropriate volumes of 0.05 M Borax and 0.1 N HCl solutions
Details on test conditions:
TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: 20 ml ampules, sterilized by autoclavation, filled with 10 ml of the test solution using aseptic techniques, and flame sealed
- Sterilisation method: membrane filtration (0.45 µm)
- Lighting: in the dark
- If no traps were used, is the test system closed/open : closed
- Is there any indication of the test material adsorbing to the walls of the test apparatus? none indicated

TEST MEDIUM
- Volume used/treatment : 10 ml test solution
- Kind and purity of water: bidistilled water
- Preparation of test medium: All experimental solutions were prepared in bidistilled water. A 200 ppm imazalil solution was prepared by dissolving 13.3 mg of imazalil sulphate in 50 ml water. Fifteen ml of the 200 ppm imazalil solution were diluted to 150 ml with the selected buffer solution and sterilized immediately by membrane filtration.

Duration:
61 d
pH:
5
Temp.:
25 °C
Initial conc. measured:
19.6 mg/L
Remarks:
mean measured value
Duration:
61 d
pH:
7
Temp.:
25 °C
Initial conc. measured:
18.5 mg/L
Remarks:
mean measured value
Duration:
61 d
pH:
9
Temp.:
25 °C
Initial conc. measured:
17.7 mg/L
Remarks:
mean measured value
Number of replicates:
14 for each pH series
Positive controls:
no
Negative controls:
no
Transformation products:
not specified
Key result
pH:
5
Temp.:
25 °C
DT50:
> 60 d
Remarks on result:
hydrolytically stable based on preliminary test
Key result
pH:
7
Temp.:
25 °C
DT50:
> 60 d
Remarks on result:
hydrolytically stable based on preliminary test
Key result
pH:
9
Temp.:
25 °C
DT50:
> 60 d
Remarks on result:
hydrolytically stable based on preliminary test
Details on results:
TEST CONDITIONS
- The range in measured pH-values did not exceed 0.05 units.

RECOVERY OF TEST SUBSTANCE
- The observed variations in imazalil concentration as a function of time in a single pH-series were clearly not larger than the scatter in the concentration values, due to experimental conditions of sample preparation and analysis. Therefore the experiment indicated that imazalil was not altered by a hydrolytic mechanism under the given experimental conditions.

The concentration Ct (mg/l) of imazalil, recovered from aqueous solutions of pH 5, 7 and 9, after various incubation periods at 25°C in the dark :

 

pH = 5

pH = 7

pH = 9

Time

(days)

Ampule

pHt

Ct

(ppm)

Mean

Ct

(ppm)

pHt

Ct

(ppm)

Mean

Ct

(ppm)

pHt

Ct

(ppm)

Mean

Ct

(ppm)

0

a

4.88

20.6

19.6

6.87

18.6

18.5

8.96

18.0

17.7

b

4.89

18.6

6.87

18.4

8.97

17.4

20

a

4.89

18.0

19.1

6.89

17.7

18.4

8.99

19.9

18.2

b

4.89

20.2

6.89

19.0

9.00

16.4

41

a

4.89

18.7

20.3

6.91

17.8

18.8

9.01

19.1

17.4

b

4.89

21.9

6.90

19.8

9.00

15.6

61

a

4.89

21.9

20.5

6.91

19.3

19.8

9.00

17.4

17.9

b

4.89

19.0

6.92

20.2

9.01

18.4

Validity criteria fulfilled:
yes
Conclusions:
The hydrolysis of imazalil was investigated according to the OECD guideline 111. Aqueous imazalil solutions of 20 ppm were incubated at pH 5, 7 and 9 at 25°C in the dark for periods up to 61 days. All of the imazalil was recovered at the end of the incubation period. The experiments indicate that chemical hydrolysis can be excluded as dissipation mechanism of imazalil in environmental systems.

Endpoint:
hydrolysis
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
Data from the related substance imazalil base is used to cover this endpoint. The justification for read across is attached in IUCLID Section 13.
Reason / purpose for cross-reference:
read-across source
Transformation products:
not specified
Key result
pH:
5
Temp.:
25 °C
DT50:
> 60 d
Remarks on result:
hydrolytically stable based on preliminary test
Key result
pH:
7
Temp.:
25 °C
DT50:
> 60 d
Remarks on result:
hydrolytically stable based on preliminary test
Key result
pH:
9
Temp.:
25 °C
DT50:
> 60 d
Remarks on result:
hydrolytically stable based on preliminary test

Description of key information

No study was available assessing hydrolysis for the target substance imazalil sulfate. A study on the imazalil 75 SP formulation was available and considered suitable as a source substance for read across. The imazalil 75 SP formulation contains exclusively 75% imazalil and 25% sulfuric acid. When diluted in water, the proportion of imazalil base- and imazalil-sulfate salt will depend on the pH in solution. At pH 3, only 0.03% of imazalil base will be present in solution. In other words, imazalil base will be almost fully protonated. At pH 6, the concentration of imazalil-sulfate and imazalil base will be roughly the same. At pH 9, only 1% imazalil-sulfate will be present in solution. Aqueous imazalil solutions were incubated at pH 5, 7 and 9 at 25°C for periods up to 61 days.

All imazalil was recovered at the end of the incubation period, indicating that chemical hydrolysis can be excluded as dissipation mechanism of imzalil in environmental systems. These results can be directly applied to imazalil sulfate (target read across substance) and result in a hydrolysis half-life > 60 days at 25°C.

Key value for chemical safety assessment

Half-life for hydrolysis:
60 d
at the temperature of:
25 °C

Additional information