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Adsorption / desorption

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Reference
Endpoint:
adsorption / desorption: screening
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:
OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method)
Version / remarks:
2000
Qualifier:
according to
Guideline:
EU Method C.18 (Adsorption / Desorption Using a Batch Equilibrium Method)
Version / remarks:
2001
GLP compliance:
yes (incl. certificate)
Remarks:
Hessisches Ministerium für Umwelt, Energie, Landwirtschaft und Verbraucherschutz, Wiesbaden, Germany
Type of method:
batch equilibrium method
Media:
soil
Radiolabelling:
no
Test temperature:
20 °C ± 2 °C
in case of the first adsorption kinetic experiment the temperature was in range of 17 to 20 °C
Analytical monitoring:
yes
Details on sampling:
- Sampling was accomplished applying the parallel method, hence as many samples with the same soil/solution ratio were prepared, as time intervals at which it was desired to study the adsorption behaviour.
- Sampling interval: after 4 h, 24 h and 48 h
Details on matrix:
Five different soils were initially used which varied in clay content, organic carbon content and pH. The following soils with typical characteristics were used:
Soil A (LUFA 2.1):
sand (pH 5.1, clay content 3.0 %, organic carbon content 0.68 %), origin: LUFA Speyer, Germany

Soil B (LUFA 6S):
clay (pH 7.2, clay content 42 %, organic carbon content 1.75 %), origin: LUFA Speyer, Germany

Soil C (LUFA 2.4):
loam (pH 7.1, clay content 27 %, organic carbon content 2.42 %), origin: LUFA Speyer, Germany

Soil D (EUROSOIL 1):
clay (pH 5.7, clay content 75.0 %, organic carbon content 3.27 %), origin: IRMM Geel, Belgium

Soil E (EUROSOIL 5):
loamy sand (pH 3.1, clay content 6.0 %, organic carbon content 5.96 %); origin: IRMM Geel, Belgium

The tests were run using air-dried fine sieved soil (< 2 mm). The dry weight content of the soil was determined. Soils were not sterilised.
The test soils were chosen based on the guidance/advice given by the OECD 106 guideline.
Details on test conditions:
TEST CONDITIONS
- Test vessels: The test vessels were made of glass and adsorbed negligible amounts of the test item.
- Buffer: 0.01 M CaCl2 solution
- pH: 3.1 - 7.2

TEST SYSTEM
- Method of preparation of test solution: The stock solution was diluted using 0.01 M CaCl2 to a concentration of 80 mg/L in 0.01 M CaCl2. Aliquots of the 80 mg/L solution were applied to soil.
- Preparation of the test soils: The soil samples were equilibrated by agitating the soil with 4 mL of 0.01 M CaCl2 solution overnight followed by addition of 0.1 mL of the stock solution.
Desorption test:
Preparation of test solutions and test soil was conducted identically to the adsorption test. After the equilibration time of 48 h the solid and liquid phases were separated by centrifugation. The aqueous phase was removed to the greatest extent possible. The volume of CaCl2 removed was replaced by an equal volume of fresh 0.01 M CaCl2. The new mixtures were agitated again and samples were taken applying a parallel method after 4 h, 24 h and 48 h. The aqueous phases were recovered after centrifugation and analysed after filtration over 0.2 μm syringe filters by HPLC coupled with UV detection.
Type:
Koc
Value:
37.5
% Org. carbon:
0.68
Remarks on result:
other: LUFA 2.1 (sand)
Type:
log Koc
Value:
1.6
% Org. carbon:
0.68
Remarks on result:
other: LUFA 2.1 (sand)
Type:
Koc
Value:
4.4
% Org. carbon:
1.72
Remarks on result:
other: LUFA 6S (clay)
Type:
log Koc
Value:
0.6
% Org. carbon:
1.72
Remarks on result:
other: LUFA 6S (clay)
Type:
Koc
Value:
12.7
% Org. carbon:
2.42
Remarks on result:
other: LUFA 2.4 (loam)
Type:
log Koc
Value:
1.1
% Org. carbon:
2.42
Remarks on result:
other: LUFA 2.4 (loam)
Type:
Koc
Value:
115.7
% Org. carbon:
3.27
Remarks on result:
other: Eurosoil 1 (clay)
Type:
log Koc
Value:
2.1
% Org. carbon:
3.27
Remarks on result:
other: Eurosoil 1 (clay)
Type:
Koc
Value:
42.1
% Org. carbon:
5.96
Remarks on result:
other: Eurosoil 5 (loamy sand)
Type:
log Koc
Value:
1.6
% Org. carbon:
5.96
Remarks on result:
other: Eurosoil 5 (loamy sand)
Adsorption and desorption constants:
Apparent desorption coefficients:
LUFA 2.1 (sand) -2.5
LUFA 6S (clay) 1.8
LUFA 2.4 (clay) -1.7
Eurosoil (loam)33.4
Eurosoil (loamy sand) 6.2
Details on results (Batch equilibrium method):
PRELIMINARY TEST
- Mass balance: 87% to 105%
- Weighed soil: ca. 2 g
- Volume of CaCl2 solution: 5, 10 and 20 mL
- Initial test substance concentration: approx. 10 mg/L

SCREENING TEST - ADSORPTION KINETICS AT ONE CONCENTRATION
- Test material stability during adsorption/desorption phase: Analyses of control samples confirmed that the test item was stable under the test conditions.

Description of key information

log Koc: 0.6 - 2.1 (OECD 106)

Key value for chemical safety assessment

Additional information

One study is available on the adsorption/desorption behaviour of Reaction mass of 2-(3,4-dimethyl-1H-pyrazol-1-yl)succinic acid and 2-(4,5-dimethyl-1H-pyrazol-1-yl)succinic acid. The study was conducted according to OECD Guideline 106 and GLP (Meinerling, 2012). Log Koc values of 0.6 - 2.1 were obtained for the five different soils tested.