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Reference
Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Qualifier:
according to guideline
Guideline:
OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method)
Deviations:
yes
Remarks:
There was no C0 control units in the tier 1 test and there was no desorption steps in the tier 2 test. None of the deviations affected the quality or integrity of the study.
GLP compliance:
yes (incl. QA statement)
Type of method:
batch equilibrium method
Media:
soil
Radiolabelling:
no
Test temperature:
The temperature was in the range of 20~25°C through the whole test period
Analytical monitoring:
yes
Details on sampling:
Tier 1-preliminary test
Equilibrium time: both the concentrations of aqueous phase and soil phase were measured on the 4th, 6th, 8th and 24th hour to calculate the adsorption percentage.

After at least 12 hours at 20~25C pre-equilibrium, 24.0 μL of stock solution of 1050.3 mg/L was added into the aqueous phase to achieve a nominal concentration of 1 mg/L. And then 4 hours agitation was run to reach adsorption equilibrium.


Matrix no.:
#1
Matrix type:
other: Paddy Soil
% Clay:
18.1
% Silt:
17.1
% Sand:
64.8
% Org. carbon:
1.14
pH:
6.88
CEC:
6.8 other: cmol/kg
Matrix no.:
#2
Matrix type:
other: meadow soil
% Clay:
10.1
% Silt:
43.4
% Sand:
46.5
% Org. carbon:
1.19
pH:
8.51
CEC:
6.8 other: cmol/kg
Matrix no.:
#3
Matrix type:
other: red soil
% Clay:
32
% Silt:
20.3
% Sand:
47.7
% Org. carbon:
0.45
pH:
5.48
CEC:
2.2 other: cmol/kg
Matrix no.:
#5
Matrix type:
other: Moister soil
% Clay:
24.6
% Silt:
24.2
% Sand:
51.2
% Org. carbon:
0.71
pH:
7.87
CEC:
3.5 other: cmol/kg
Matrix no.:
#4
Matrix type:
other: Black soil
% Clay:
14.5
% Silt:
35.4
% Sand:
50.1
% Org. carbon:
2.51
pH:
6.54
CEC:
34.1 other: cmol/kg
Details on matrix:
The soils was sieved through 2 mm and stored under room temperature. The characteristics are listed in the following table:
Soil type Batch No. Soil location

Paddy Soil 20170206 Huai’an, Jiangsu province
Meadow soil 20150707 Zhangye, Gansu province
Red Soil 20151209 Yangchun, Guangdong province
Black Soil 20150717 Ji’an, Jilin province
Moisture soil 20150906-3 Heze, Shandong province
Key result
Sample No.:
#1
Type:
log Koc
Value:
3.3 dimensionless
Matrix:
Paddy soil
Key result
Sample No.:
#2
Type:
log Koc
Value:
3.5 dimensionless
Matrix:
Medow soil
Key result
Sample No.:
#3
Type:
log Koc
Value:
3.7 dimensionless
Matrix:
Red soil
Key result
Sample No.:
#4
Type:
log Koc
Value:
3.1 dimensionless
Matrix:
Black soil
Key result
Sample No.:
#5
Type:
log Koc
Value:
3.8 dimensionless
Matrix:
Moister soil
Recovery of test material:
The recovery test in 0.01 mol/L CaCl2 solution was set two concentrations, i.e. 0.001 mg/L and 1 mg/L, the mean recovery rate was in the range of 93.7%~104.7% with RSD in the range of 4.1%~14.3%. The recovery test in soils was set two concentrations, i.e. 0.5 mg/kg and 5 mg/kg, the mean recovery rate was in the range of 91.1 %~110.5% with RSD in the range of 1.9%~10.9%.
Concentration of test substance at end of desorption equilibration period:
After 4 hour adsorption agitation, another two parallel samples were subjected to desorption phase for 8 hours. The desorption rates of all the five concentrations in red soil was in the range of 0~24.4% in the red soil, 0.9%~11.4% in the black soil, 0~8.7% in the paddy soil, 3.7%~62.2% in the moisture soil and 6.5%~15.7% in the aquic-brown soil, respectively. Because the desorption rates were all <75%, the adsorption of test item on these five soils was thought to be irreversible.
Sample no.:
#1
Duration:
4 h
% Adsorption:
97.8
Sample no.:
#2
Duration:
4 h
% Adsorption:
97.7
Sample no.:
#3
Duration:
4 h
% Adsorption:
89.9
Sample no.:
#4
Duration:
4 h
% Adsorption:
89.9
Sample no.:
#5
Duration:
4 h
% Adsorption:
95.1
Transformation products:
not measured
Validity criteria fulfilled:
yes
Conclusions:
The red soil, black soil, paddy soil, moisture soil and aquic-brown soil were employed in adsorption isotherms test, the solution/soil ratio was 5:1, and 4 hours as the equilibrium time; the concentrations were 0.01 mg/L, 0.05 mg/L, 0.1 mg/L, 0.5 mg/L and 1 mg/L. The log Koc of red soil, black soil, paddy soil, moisture soil and aquic-brown soil was 3.7, 3.1, 3.3, 3.8 and 3.5, respectively. The test item Ethylene glycol dibenzoate has a moderate adsorption potential, and the adsorption was deduced as irreversible.
Executive summary:

The GC/MS/MS instrument was employed to determine the test item Ethylene glycol dibenzoate. The recovery test in 0.01 mol/L CaCl2solution was set two concentrations, i.e. 0.001 mg/L and 1 mg/L, the mean recovery rate was in the range of 93.7%~104.7% with RSD in the range of 4.1%~14.3%. The recovery test in soils was set two concentrations, i.e. 0.5 mg/kg and 5 mg/kg, the mean recovery rate was in the range of 91.1 %~110.5% with RSD in the range of 1.9%~10.9%. The present analytical method met the quality criteria.

Abatch equilibrium method was performed on the basis of OECD Guideline for the Testing of Chemicals. No.106: Adsorption/desorption Using a Batch Equilibrium Method.

The red soil, black soil, paddy soil, moisture soil and aquic-brown soil were employed inadsorption isotherms test,the solution/soil ratio was 5:1, and 4 hours as the equilibrium time; the concentrations were 0.01 mg/L, 0.05 mg/L, 0.1 mg/L, 0.5 mg/L and 1 mg/L. The log Kocof the test item on red soil, black soil, paddy soil, moisture soil and aquic-brown soil was 3.7, 3.1, 3.3, 3.8 and 3.5, respectively. The test item Ethylene glycol dibenzoate has a moderate adsorption potential, and the adsorption was deduced as irreversible.

Description of key information

A batch equilibrium method was performed on the basis of OECD Guideline for the Testing of Chemicals. No.106: Adsorption/desorption Using a Batch Equilibrium Method.

The red soil, black soil, paddy soil, moisture soil and aquic-brown soil were employed in adsorption isotherms test, the solution/soil ratio was 5:1, and 4 hours as the equilibrium time; the concentrations were 0.01 mg/L, 0.05 mg/L, 0.1 mg/L, 0.5 mg/L and 1 mg/L. The log Koc of the test item on red soil, black soil, paddy soil, moisture soil and aquic-brown soil was 3.7, 3.1, 3.3, 3.8 and 3.5, respectively.

The average log Koc of the five soils is 3.48 which corresponds to a Koc of 3020.

Key value for chemical safety assessment

Koc at 20 °C:
3 020

Additional information

[LogKoc: 3.48]