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Reference
Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
key study
Study period:
from 2021-0125 to 2021-03-19
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
EU Method C.18 (Adsorption / Desorption Using a Batch Equilibrium Method)
Qualifier:
according to guideline
Guideline:
OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method)
Principles of method if other than guideline:
The Freundlich adsorption isotherm was not determined. The desorption behavior of the test item was not investigated. These deviations from the guideline are on request of the sponsor.
The extraction efficiency of the soil extraction method was lower than 90%. Despite extensive method development for the extraction, this efficiency could not be optimized.
This deviation is considered to have no impact on the quality and integrity of the study.
GLP compliance:
yes (incl. QA statement)
Type of method:
batch equilibrium method
Media:
soil
Specific details on test material used for the study:
Three components, o-TDA-1EO-3PO, o-TDA-2EO-5PO and o-TDA-3EO-6PO, of the UVCB substance oTDA-EO-PO, were selected as being representative and analysed in aqueous phases as well as in soil extracts.
Radiolabelling:
no
Test temperature:
The temperature was in the range of 20 to 25 °C during the course of the study.
Analytical monitoring:
yes
Details on sampling:
- Concentrations: 2 mg/L
- Sampling interval: Tier 2: 2 h, 4 h, 24 h, 48 h and 72 h
Details on matrix:
Standard LUFA soils 2.1, 2.2, 2.3 and 2.4 as well as Eurosoil 2 in contact to 0.01 M CaCl2-solution were used for this study. These matrices have varying adsorption capacities in relation to their content of organic matter, clay, pH and cation exchange capacity. (see table 1)
COLLECTION AND STORAGE
-Origin of soils:
LUFA soils:Landwirtschaftliche Untersuchungs- und Forschungsanstalt LUFA Speyer. Obere Langgasse 40. 67346 Speyer, Germany
Eurosoils: European Commission, Joint Research Centre. Institute for Reference Materials and Measurements IRMM; Retieseweg. B-2440 Geel, Belgium
- Storage conditions:
Eurosoils: Room temperature. in brown glass bottles
LUFA soils: Room temperature. in closed containers
- Soil preparation (e.g.: 2 mm sieved; air dried etc.):

PROPERTIES
Please see table 1 for details
Details on test conditions:
TEST CONDITIONS
- pH: see table 1
- Temperature: 20-25 °C

TEST SYSTEM
- Reaction vessel: 50 mL polypropylene centrifugation tubes
- Water filtered (i.e. yes/no; type of size of filter used, if any):
- Amount of soil/sediment/sludge and water per treatment (if simulation test):
- Soil/sediment/sludge-water ratio (if simulation test):
- Number of reaction vessels/concentration:
- Measuring equipment:
- Test performed in closed vessels due to significant volatility of test substance:
- Test performed in open system:
- Method of preparation of test solution:
- Are the residues from the adsorption phase used for desorption:
- Other:
Sample No.:
#1
Duration:
24 h
Remarks:
o-TDA-2EO-5PO
Sample No.:
#3
Duration:
72 h
Remarks:
o-TDA-3EO-6PO
Sample No.:
#2
Duration:
48 h
Remarks:
o-TDA-1EO-3PO
Sample No.:
#2
Duration:
72 h
Remarks:
o-TDA-2EO-5PO
Sample No.:
#5
Duration:
48 h
Remarks:
o-TDA-2EO-5PO
Sample No.:
#5
Duration:
72 h
Remarks:
o-TDA-1EO-3PO
Sample No.:
#1
Duration:
72 h
Remarks:
o-TDA-3EO-6PO
Key result
Sample No.:
#3
Type:
log Koc
Remarks:
o-TDA-3EO-6PO
Value:
5.35 dimensionless
Matrix:
LUFA 2.3: Sandy loam (see table 1)
% Org. carbon:
0.412
Key result
Sample No.:
#2
Type:
log Koc
Remarks:
o-TDA-1EO-3PO
Value:
5.25 dimensionless
Matrix:
LUFA 2.2: Loamy sand (see table 1)
% Org. carbon:
1.47
Key result
Sample No.:
#2
Type:
log Koc
Remarks:
o-TDA-2EO-5PO
Value:
5.21 dimensionless
Matrix:
LUFA 2.2. loamy sand (see table 1)
% Org. carbon:
1.47
Sample No.:
#5
Type:
log Koc
Remarks:
o-TDA-2EO-5PO
Value:
3.68 dimensionless
Matrix:
Eurosoil 2: Silt loam (see table 1)
% Org. carbon:
3.72
Sample No.:
#5
Type:
log Koc
Remarks:
o-TDA-1EO-3PO
Value:
3.46 dimensionless
Matrix:
Eurosoil 2: Silt loam (see table 1)
% Org. carbon:
3.72
Sample No.:
#1
Type:
log Koc
Remarks:
o-TDA-3EO-6PO
Value:
3.45 dimensionless
Matrix:
LUFA 2.1: Loamy sand (see table 1)
% Org. carbon:
0.718
Adsorption and desorption constants:
see table 3
Recovery of test material:
The recovery rate for soil extracts was below 90%. The extraction efficiency could not be optimized, presumably due to rapid formation of NER. See table 4a-c for details.
Remarks on result:
other: see table 4 a-c
Transformation products:
not specified

Table 2: Tier 2 - Adsorption Kinetics - Results


Applied nominal test item concentration: 2 mg/L; n = 2;
Mobility according to McCall et al. (1980): KOC 0 – 50 very high, KOC 50 – 150 high, KOC 150 – 500 medium, KOC 500 – 2000 low, KOC 2000 – 5000 slight, KOC > 5000 immobile



















































































































































































































Matrix



pH Value


1)



MB


[%]



teq


[h]



Direct Method



Indirect Method



Kd


[mL/g]



KOC


[mL/g]



Mobility according to McCall et al.



Kd


[mL/g]



KOC


[mL/g]



Mobility according to McCall et al.



o-TDA-1EO-3PO



LUFA 2.1



5.8



26



48



-0.0001



-0.02



very high



138



19263



immobile



LUFA 2.2



6.2



1



48



-0.0002



-0.01



very high



2642



179728



immobile



LUFA 2.3



6.4



8



72



-0.0002



-0.04



very high



590



143086



immobile



LUFA 2.4



7.9



7



72



-0.00008



-0.004



very high



795



42957



immobile



Eurosoil 2



7.5



32



72



-0.00003



-0.001



very high



108



2898



slight



o-TDA-2EO-5PO



LUFA 2.1



5.8



54



24



-0.00006



-0.009



very high



45



6294



immobile



LUFA 2.2



6.2



2



72



0.0004



0.02



very high



2408



163790



immobile



LUFA 2.3



6.4



8



72



0.0004



0.09



very high



643



156075



immobile



LUFA 2.4



7.9



10



72



0.001



0.06



very high



524



28320



immobile



Eurosoil 2



7.5



31



48



0.01



0.3



very high



179



4819



slight



o-TDA-3EO-6PO



LUFA 2.1



5.8



72



72



-0.00004



-0.005



very high



20



2789



slight



LUFA 2.2



6.2



4



48



0.0006



0.04



very high



1745



118720



Immobile



LUFA 2.3



6.4



5



72



0.0004



0.09



very high



927



224884



Immobile



LUFA 2.4



7.9



4



72



0.003



0.2



very high



1502



81206



Immobile



Eurosoil 2



7.5



31



48



0.05



1



very high



429



11534



Immobile



 


Table 3: Kd and KOC Values for the three selected Components after equilibrium time


teq              = equilibrium time; time to reach the adsorption plateau






































































































Soil Type



o-TDA-1EO-3PO



o-TDA-2EO-5PO



o-TDA-3EO-6PO



 



teq


[h]



Kd


[ml/g]



KOC


[ml/g]



Log


 KOC



teq


[h]



Kd


[ml/g]



KOC


[ml/g]



Log


 KOC



teq


[h]



Kd


[ml/g]



KOC


[ml/g]



Log


 KOC



LUFA 2.1



48



138



19263



4.28



24



45



6294



3.80



72



20



2789



3.45



LUFA 2.2



48



2642



179728



5.25



72



2408



163790



5.21



48



1745



118720



5.07



LUFA 2.3



72



590



143086



5.16



72



643



156075



5.19



72



927



224884



5.35



LUFA 2.4



72



795



42957



4.63



72



524



28320



4.45



72



1502



81206



4.91



Eurosoil 2



72



108



2898



3.46



48



179



4819



3.68



48



429



11534



4.06



 


Table 4: Mass Ballance;


RR   = Recovery Rate, ‘-1%’ is calculated if the amount in the pore water is higher than in the soil extracts


nominal concentration, test item: 2 mg/L, n = 2


a) o-TDA-1EO-3PO


























































































































































Sampling point [h]



2



4



24



48



72



Soil Type



LUFA 2.1



RR aqueous phase [%]



49



53



30



28



26



RR solid phase [%]



0



0



0



0



0



Mass balance [%]



48



53



30



28



26



Soil Type



LUFA 2.2



RR aqueous phase [%]



63



52



17



3



1



RR solid phase [%]



-1



-1



0



0



0



Mass balance [%]



62



51



17



3



1



Soil Type



LUFA 2.3



RR aqueous phase [%]



84



59



46



15



8



RR solid phase [%]



-1



-1



0



0



0



Mass balance [%]



82



59



45



15



8



Soil Type



LUFA 2.4



RR aqueous phase [%]



59



41



29



10



7



RR solid phase [%]



-1



0



0



0



0



Mass balance [%]



59



41



29



10



7



Soil Type



Eurosoil 2



RR aqueous phase [%]



93



70



44



30



32



RR solid phase [%]



-1



0



0



0



0



Mass balance [%]



92



70



45



31



32



b) o-TDA-2EO-5PO


























































































































































Sampling point [h]



2



4



24



48



72



Soil Type



LUFA 2.1



RR aqueous phase [%]



84



77



54



51



55



RR solid phase [%]



-1



0



0



0



0



Mass balance [%]



83



76



54



51



55



Soil Type



LUFA 2.2



RR aqueous phase [%]



79



69



30



6



2



RR solid phase [%]



-1



1



0



0



0



Mass balance [%]



79



70



30



6



2



Soil Type



LUFA 2.3



RR aqueous phase [%]



89



90



55



20



7



RR solid phase [%]



1



2



0



0



0



Mass balance [%]



90



91



55



20



8



Soil Type



LUFA 2.4



RR aqueous phase [%]



72



55



35



19



10



RR solid phase [%]



5



6



4



1



0



Mass balance [%]



77



61



39



19



10



Soil Type



Eurosoil 2



RR aqueous phase [%]



69



63



31



23



22



RR solid phase [%]



11



12



11



8



9



Mass balance [%]



80



76



42



31



31



c) o-TDA-3EO-6PO


























































































































































Sampling point [h]



2



4



24



48



72



Soil Type



LUFA 2.1



RR aqueous phase [%]



90



76



81



63



72



RR solid phase [%]



0



0



1



0



0



Mass balance [%]



89



76



82



63



72



Soil Type



LUFA 2.2



RR aqueous phase [%]



85



73



26



4



2



RR solid phase [%]



1



2



0



0



0



Mass balance [%]



86



76



26



4



2



Soil Type



LUFA 2.3



RR aqueous phase [%]



87



86



40



13



5



RR solid phase [%]



2



3



1



0



0



Mass balance [%]



88



89



41



13



5



Soil Type



LUFA 2.4



RR aqueous phase [%]



74



56



27



10



4



RR solid phase [%]



11



13



6



1



0



Mass balance [%]



85



69



33



12



4



Soil Type



Eurosoil 2



RR aqueous phase [%]



32



32



13



11



10



RR solid phase [%]



35



37



25



20



22



Mass balance [%]



67



69



38



31



32



 

Validity criteria fulfilled:
yes
Conclusions:
It was found that the three selected components had a strong tendency to adsorb on soil and the equilibrium was mainly completely achieved after 72 hours.
Executive summary:

The adsorption behavior of the test item was investigated on five different soils according to OECD guideline 106 and Council Regulation (EC) No. 440/2008, C.18 (Tier 1 and Tier 2). Three components, o-TDA-1EO-3PO, o-TDA-2EO-5PO and o-TDA-3EO-6PO, of the UVCB substance oTDA-EO-PO, were selected as being representative and analysed in aqueous phases as well as in soil extracts. The determination for adsorption kinetics was performed with a nominal test item concentration of 2 mg test item/L. A soil / solution ratio of 1:50 was used. The concentrations of the test item were measured in aqueous phase and soil extracts at defined sampling points. The sampling points were 2 h, 4 h, 24 h, 48 h and 72 h. The test item was analysed via LC-MS/MS. It was found that the three selected components had a strong tendency to adsorb on soil and the equilibrium was mainly completely achieved after 72 hours. The measured log Koc reached from 3.46 (o-TDA-1EO-3PO at Eurosoil 2) to 5.35 (o-TDA-3EO-6PO at LUFA 2.3).


The Freundlich adsorption isotherm was not determined. The desorption behavior of the test item was not investigated. These deviations from the guideline are on request of the sponsor.
The extraction efficiency of the soil extraction method was lower than 90%. Despite extensive method development for the extraction, this efficiency could not be optimized.
This deviation is considered to have no impact on the quality and integrity of the study.

Description of key information

The three representative structures of the UVCB found to have a strong tendency to adsorp to thesoil phase with log Koc values ranging from 3.46 (o-TDA-1EO-3PO at Eurosoil 2) to 5.35 (o-TDA-3EO-6PO at LUFA 2.3) (NLP Polyols Consortium, 2021)..

Key value for chemical safety assessment

Additional information

An experimental study according to OECD guideline 106 and Council Regulation (EC) No. 440/2008, C.18 (Batch equilibrium method) with five different soil types was conducted to assess the adsorption behavior of the UVCB substance. Three components, o-TDA-1EO-3PO, o-TDA-2EO-5PO and o-TDA-3EO-6PO, of the UVCB substance oTDA-EO-PO, were selected as being representative and analysed in aqueous phases as well as in soil extracts. The determination for adsorption kinetics was performed with a nominal test item concentration of 2 mg test item/L at 20 -25 °C test temperature. A soil / solution ratio of 1:50 was used. The concentrations of the test item were measured in aqueous phase and soil extracts at defined sampling points. The sampling points were 2 h, 4 h, 24 h, 48 h and 72 h. The test item was analysed via LC-MS/MS. It was found that the three selected components had a strong tendency to adsorb on soil and the equilibrium was mainly completely achieved after 72 hours. The measured log Koc reached from 3.46 (o-TDA-1EO-3PO at Eurosoil 2) to 5.35 (o-TDA-3EO-6PO at LUFA 2.3). The Koc ranged from 2789 to 224884 ml/g (NLP Polyols Consortium, 2021).


These results are expected to provide a more realistic determination of adsorption potential than the HPLC estimation method, which may be confounded by the surface-activity of the test substance components and lack of relevant reference substances (i.e., aromatic, alcohols, ethers, amines) employed in the OECD 121 guideline.Furthermore, because the HPLC method does not account for the cation-exchange mode of adsorption, it may not correctly predict the adsorption of the test substance components which possess cationic amino-groups.