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Environmental fate & pathways

Adsorption / desorption

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Reference
Endpoint:
adsorption / desorption, other
Remarks:
adsorption
Type of information:
(Q)SAR
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification
Justification for type of information:
1. SOFTWARE
ChemProp(TM) Main Module 6.5, Public OSIRIS Edition

2. MODEL (incl. version number)
Franco, Fu & Trapp (Partitioning, soil sorption coefficient, Koc), ionizable substances, acids and bases

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
See “Test material information”

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
See attached information on the model provided by the developer. Further information on the OECD criteria as outlined by the applicant is provided below under "Any other information of materials and methods incl. tables"

5. APPLICABILITY DOMAIN
See attached information and information as provided in "Any other information on results incl. tables".

6. ADEQUACY OF THE RESULT
See assessment of adequacy as outlined in the "Overall remarks, attachments" section.
Qualifier:
according to
Version / remarks:
REACH Guidance on QSARs R.6
Principles of method if other than guideline:
- Software tool(s) used including version: ChemProp v6.5
- Model(s) used: Franco, Fu & Trapp
Full reference and details of the used formulas can be found in:
1. Franco A, Fu W, Trapp S 2009. Influence of soil pH on the sorption of ionizable chemicals: Modeling advances. Environ. Toxicol. Chem. 28: 458-464.
2. Franco A, Trapp S 2008. Estimation of the soil-water partition coefficient normalized to organic carbon for ionizable organic chemicals. Environ. Toxicol. Chem. 27: 1995-2004.
- Model description: see field 'attached justification' and 'any other information on material and methods'
- Justification of QSAR prediction: see field 'Justification for type of information', 'Attached justification' and/or 'overall remarks'
GLP compliance:
no
Type of method:
other: calculation
Media:
soil
Details on test conditions:
BASIS FOR CALCULATION OF Koc:
- Estimation software: ChemProp v6.5, Franco, Fu and Trapp 2009 model for acids
- Log Kow: 2.53 at 25 °C, pH 5.5 (EU Method A.8 - Appendix 1, Estimation method)
- pKa: 3.76 (calculated via SPARC v4.6)
- pH: 4/ 7/ 9
Type:
Koc
Value:
228.394 L/kg
pH:
4
% Org. carbon:
5
Remarks on result:
other: based on eq. 2 (acids)
Type:
log Koc
Value:
2.36 dimensionless
pH:
4
% Org. carbon:
5
Remarks on result:
other: based on eq. 2 (acids)
Type:
Koc
Value:
66.35 L/kg
pH:
7
% Org. carbon:
5
Remarks on result:
other: based on eq. 2 (acids)
Type:
log Koc
Value:
1.82 dimensionless
pH:
7
% Org. carbon:
5
Remarks on result:
other: based on eq. 2 (acids)
Type:
Koc
Value:
65.82 L/kg
pH:
9
% Org. carbon:
5
Remarks on result:
other: based on eq. 2 (acids)
Type:
log Koc
Value:
1.82 dimensionless
pH:
9
% Org. carbon:
5
Remarks on result:
other: based on eq. 2 (acids)

For detailed information on the results please refer to the attached report.

Description of key information

Log Koc 1.82 (pH 7, QSAR: Chemprop v.6.5)

Key value for chemical safety assessment

Koc at 20 °C:
66.35

Additional information

There is no experimental study available, in which the log Koc of 4-(octadecylamino)-4-oxoisocrotonic acid (CAS 3077-27-8) was assessed. Considering the ionization properties of the substance, the adsorption potential has been calculated using Franco, Fu and Trapp‘s expressions (2009) on estimation of the organic carbon-water partitioning coefficient of ionisable organic substances. The log Kow for the neutral molecule, the pH as well as the pKa values were used as input parameters. The required input parameters for the calculations using ChemProp are the environmentally relevant pKa value (3.76 at pH 4, 7 and 9, calculated with SPARC v4.6) as well as the log Kow 2.53 (at 25 °C, pH 5.5 (EU Method A.8 - Appendix 1, Estimation method)).

The log Koc was calculated to be 2.36 at pH 4, 1.82 at pH 7 and pH 9. These values indicate a low adsorption potential of the substance to particulate matter in soils and sediments. According to the Guidance on Information Requirements and Chemical Safety Assessment, Chapter R.7.1.8.5 the log D value for the ionized molecule determined around the default pH of 7 is considered more relevant, compared to pH 4 or 9 for chemical safety assessment (ECHA Guidance R.7a 'Guidance on information requirements and chemical safety assessment' (ECHA, 2017). Therefore , the calculated log Koc of 1.83 (Koc = 66.35) at pH 7 has been used as key value for the chemical safety assessment.