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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:
15 Oct - 18 Dec 2014
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Qualifier:
according to
Guideline:
EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)
GLP compliance:
yes (incl. certificate)
Remarks:
Staatliches Gewerbeaufsichtsamt Hildesheim, Germany
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
- Sampling intervals for the parent/transformation products: In the preliminary test, samples were taken at 0 h and 120 h. The main test was performed at pH4 and samples were taken after: 0, 13.9, 62.1, 86.0, 159, 206, 256, 326, 421, 547 and 710 h (pH4, 20 °C); 0, 13.4, 61.7, 85.5, 158, 206, 255, 325, 420, 546, 709 h (pH4, 30 °C); 0, 12.9, 61.1, 84.9, 158, 184, 205, 255, 261, 325 h (pH4, 50 °C)
- Sampling intervals/times for pH measurements: The pH was measured before start of hydrolysis.
- Sampling intervals/times for sterility check: Sterility was checked at test end by colony forming units (CFU)-determination.
- Sample storage conditions before analysis: Samples were analysed immediately (if possible less than 30 min until start of analysis, but at least not more than 5% of the total run time).
Buffers:
- pH: 4
- Composition of buffer: 0.18 g of NaOH and 5.7555 g of mono potassium citrate were dissolved in 500 mL double distilled water

- pH: 7
- Composition of buffer: 0.7358 g of NaOH and 4.3012 g of KH2PO4 were dissolved in 500 mL double distilled water

- pH: 9
- Composition of buffer: 0.426 g NaOH, 1.8638 g KCl and 1.5458 g H3BO3 were dissolved in 500 mL double distilled water

Buffers were purged with nitrogen for 5 min and then the pH was checked to a precision of at least 0.1 at the test temperatures.
Details on test conditions:
TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: HPLC vials, volume: 4 mL
- Sterilisation method: Buffers were sterilised by filtration through 0.2 µm.
- Lighting: Photolytic effects were avoided using opaque water baths.
- Open/Closed: vials were sealed
- Is there any indication of the test material adsorbing to the walls of the test apparatus? no

TEST MEDIUM
- Volume used/treatment: 4 mL
- Kind and purity of water: double distilled water
- Preparation of test medium: Sterile buffer solutions were spiked to a test substance concentration of 250 mg/L and filled into test vials.
- Renewal of test solution: no
- Identity and concentration of co-solvent: acetonitrile, ≤ 1% (v/v)

OTHER TEST CONDITIONS
- Adjustment of pH: no
Duration:
120 h
pH:
4
Temp.:
50 °C
Initial conc. measured:
250 mg/L
Duration:
120 h
pH:
7
Temp.:
50 °C
Initial conc. measured:
250 mg/L
Duration:
120 h
pH:
9
Temp.:
50 °C
Initial conc. measured:
250 mg/L
Duration:
710 h
pH:
4
Temp.:
20 °C
Initial conc. measured:
242 mg/L
Duration:
709 h
pH:
4
Temp.:
30 °C
Initial conc. measured:
242 mg/L
Duration:
325 h
pH:
4
Temp.:
50 °C
Initial conc. measured:
242 mg/L
Number of replicates:
Duplicates per pH value and sampling date
Positive controls:
no
Negative controls:
yes
Remarks:
buffer solutions at pH4, 7 and 9
Preliminary study:
The degradation after 120 h of incubation at 50 °C was 58.2% at pH4 and 0% at pH7 and pH9.
Transformation products:
not measured
% Recovery:
93.8
pH:
4
Temp.:
20 °C
Duration:
710 h
% Recovery:
67.36
pH:
4
Temp.:
30 °C
Duration:
709 h
% Recovery:
14.71
pH:
4
Temp.:
50 °C
Duration:
325 h
pH:
4
Temp.:
20 °C
Hydrolysis rate constant:
0 s-1
DT50:
286 d
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: r²: 0.581; Confidence interval: 285 - 1264 d
pH:
4
Temp.:
30 °C
Hydrolysis rate constant:
0 s-1
DT50:
49.2 d
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: r²: 0.994; Confidence interval: 49.2 - 54.7 d
pH:
4
Temp.:
50 °C
Hydrolysis rate constant:
0 s-1
DT50:
4.83 d
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: r²: 0.996; Confidence interval: 4.83 - 5.33 d
Other kinetic parameters:
For all temperature conditions of the advanced test the ln concentration vs. time plots have regression graphs with slopes significantly non zero. Therefore first / pseudo first order reaction kinetic was applied for data computation. A confirmation of first / pseudo first order reaction kinetic with coefficients of determination > 0.8 could be obtained for the 30 °C and 50 °C test conditions. For the 20 °C test condition, due to the observed high half life a coefficient of determination < 0.8 was calculated. Nevertheless, the first / pseudo first order kinetic model was regarded as acceptable and used for evaluation.
Details on results:
TEST CONDITIONS
- pH, sterility, temperature, and other experimental conditions maintained throughout the study: Yes

The test item showed only a slow hydrolysis (t1/2> 40 d) at pH 4 at 20 and 30 °C as well as a moderate hydrolysis (t1/230 d) at 50 °C. At pH 7 and 9 no significant elimination was observed in the preliminary test and therefore the test item was considered as hydrolytically stable under this condition and a half-life of > 1 year could be assumed for environmental typical temperatures.

Validity criteria fulfilled:
yes
Conclusions:
The hydrolysis study according to OECD 111 resulted in hydrolysis < 10% after 5 d at pH 7 and 9 and 50 °C. Thus, a DT50 > 1 yr at pH 7 and 9 (25 °C) was extrapolated in accordance with the guideline. A main test was performed for pH 4 at 20, 30 and 50 °C for 13.5 - 29.58 d resulting in DT50 values of 286 d (20 °C), 49.2 d (30 °C) and 4.83 d (50 °C). Thus, the substance hydrolyses slowly under environmental conditions.

Description of key information

The hydrolysis study according to OECD 111 resulted in hydrolysis < 10% after 5 d at pH 7 and 9 and 50 °C. Thus, a DT50 > 1 yr at pH 7 and 9 (25 °C) was extrapolated in accordance with the guideline. A main test was performed for pH 4 at 20, 30 and 50 °C for 13.5 - 29.58 d resulting in DT50 values of 286 d (20 °C), 49.2 d (30 °C) and 4.83 d (50 °C).Thus, the substance hydrolyses slowly under environmental conditions.

Key value for chemical safety assessment

Additional information

One experimental study is available investigating the hydrolytic properties of the substance. The study was performed according to OECD 111 (GLP). A preliminary test with a concentration of approx. 250 mg/L was performed at 3 different pH values (pH 4, 7 and 9) and 50 °C for 120 h. The result from HPLC-DAD analysis indicated that the test substance is hydrolytically stable at pH 7 and 9 at 50 °C. Recovery of the substance at pH7 and pH9 was 100% at both pH levels. Thus, in accordance with the guideline no main test was considered necessary for pH 7 and 9 and the results from the preliminary test were extrapolated to 25 °C. At 25 °C the DT50 of the test substance was estimated to be > 1 yr at pH 7 and 9.
At pH 4 only 41.8% of the substance was found after 120 h in the preliminary test. Since hydrolysis was > 10% for pH4 a main test at three different temperatures (20, 30 and 50 °C) was performed. The main test lasted for 29.58 d (20 °C), 29.54 d (30 °C), 13.5 d (50 °C). DT50 values of 286 d (20 °C), 49.2 d (30 °C) and 4.83 d (50 °C) resulted. In conclusion, the test substance hydrolyses slowly under environmental conditions.