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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
Study period:
not reported
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Remarks:
Non GLP study. The study was conducted according to a method equivalent to the OECD 106 guideline without major deviations. However, no data on test conditions are reported.
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method)
Version / remarks:
von Oepen et al., 1989, 1990
Deviations:
no
GLP compliance:
no
Type of method:
batch equilibrium method
Media:
soil
Radiolabelling:
no
Test temperature:
not specified
Analytical monitoring:
yes
Details on sampling:
After reaching the equilibrium the soil samples were centrifuged, decanted, and the concentrations in the supernatant were determined by means of GC, HPLC or scintillation measurements (von Oepen 1990). All samples were determined in parallel. One control and one blank were investigated additionally.
Matrix no.:
#1
Matrix type:
Podzol
% Clay:
2.6
% Silt:
8.2
% Sand:
89.2
% Org. carbon:
4.85
pH:
2.8
CEC:
15.1 meq/100 g soil d.w.
Matrix no.:
#2
Matrix type:
Alfisol
% Clay:
15.9
% Silt:
14.4
% Sand:
69.7
% Org. carbon:
1.25
pH:
6.7
CEC:
12.3 meq/100 g soil d.w.
Matrix no.:
#3
Matrix type:
other: Sediment
% Clay:
35.7
% Silt:
58.8
% Sand:
5.5
% Org. carbon:
1.58
pH:
7.1
CEC:
13.4 meq/100 g soil d.w.
Details on matrix:
The soils used for testing were selected under support of Prof. Fräinzle and Brümmer (von Oepen 1989) considering representativity for the FRG and covering a broad spectrum of sorption relevant properties e.g. organic carbon content (% oc), clay content , pH value, Cation Exchange Capacity etc.. The soils used for testing were an acidic forest soil, a Podzol and an agricultural soil (Alfisol). Additionally the sorption behaviour of a sublimnic soil, a
sediment of the Lake Constance, was investigated.
Details on test conditions:
TEST SYSTEM
- Method of preparation of test solution: The preparation of the soils for testing, e.g. homogenization, sterilization etc., in order to obtain reproducible results was described in an earlier publication (von Oepen et al. 1989). First the sorption kinetics were determined for special selected compounds of each substance class according to the OECD-Guideline 106 (c.f.e.g. von Oepen 1989). 50 mL of the test solution were added to 10 g (dry weight) of the specific soils. The soil samples were shaken for 0.5, 1, 1.5, 5, 24 respectively 72 hours. Then an aliquot of 1 mL of the water-phase was removed and the concentration of the substance in the aqueous phase was determined. As for all investigated substances the sorption equilibrium was reached within 16 hours, the Freundlich isotherms were determined after an incubation period of 16 hours. The initial concentrations used were about 15 mg/L, 5 mg/L, 0.5 and 0.15 mg/L.
Key result
Type:
Koc
Value:
125 dimensionless
Matrix:
Alfisol
% Org. carbon:
1.25
Type:
Koc
Value:
162 dimensionless
Matrix:
Podzol
% Org. carbon:
4.85
Type:
Koc
Value:
92 dimensionless
Matrix:
Sediment
% Org. carbon:
1.58
Duration:
16 h
% Desorption:
> 80
Validity criteria fulfilled:
yes
Conclusions:
The modified batch-equilibrium method was applied for the determination of the adsorption coefficient (Koc) of the test substance. The mean Koc was determined to be 128. The results of the test can be considered reliable without restriction.

Description of key information

This endpoint is covered with a non GLP-study (key, publication, von Oepen, 1991) performed according to the modified test guideline OECD 106. The mean Koc of butyl benzoate was determined to be 128 using the batch-equilibrium method.

Key value for chemical safety assessment

Koc at 20 °C:
128

Additional information

[LogKoc: 2.11]