Carboxylic acids, di-, C4-6

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

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

Estimation Program Interface (EPI) Suite
2. MODEL (incl. version number)
KOCWIN v2.00 included in EPI-Suite v 4.11, 2000-2012.
3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
A SMILES notation (OC(=O)CCCCC(=O)O) was entered in the initial data entry screen.
4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL AND APPLICABILITY DOMAIN
a) Domains:
i. Molecular weights:
With a molecular weight of 146.14 g/mol the substance is within the range of the training set (32 - 665 g/mol) as well as in the range of the validation set (27 – 991 g/mol).
ii. Structural fragment domain:
Regarding the structure of adipic acid the fragment descriptors found by the program are complete and listed in Appendix D (KOCWIN Fragment and Correction Factor descriptors).
iii. Mechanism domain:
No information available.
iv. Metabolic domain, if relevant:
Not relevant.
b) Structural analogues: no information available
c) Considerations on structural analogues: no information available
3.4 The uncertainty of the prediction (OECD principle 4)
Adipic acid is not highly complex and the rules applied for the substance appear appropriate. An individual uncertainty for the investigated substance is not available.
5. ADEQUACY OF THE RESULT
Regulatory purpose:
The data may be used under any regulatory purpose.
Approach for regulatory interpretation of the model result:
If no experimental data are available, the estimated value may be used to fill data gaps needed for hazard and risk assessment, classification and labelling and PBT / vPvB assessment. Further the value is used for other calculations.
Outcome:
The prediction of organic carbon partition coefficient yields a useful result for further evaluation.
Conclusion:
The result is considered as useful for regulatory purposes.

Reason / purpose for cross-reference:

read-across: supporting information

Principles of method if other than guideline:

QSAR Estimation Method: KOCWIN v2.00 included in EPI-Suite v 4.11, 2000-2012

GLP compliance:

no

Remarks:

Calculation model, thus no GLP compliance required.

Type of method:

other: calculated

Media:

soil

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material
PHYSICO-CHEMICAL PROPERTIES
[*) Properties that should be provided for the HPLC method]
- Vapour pressure: 0.097 hPa at 18.5°C (Kirk-Othmer)
- Water solubility*: 23 g/L at 25°C (MITI, 1992)
- Solubility in organic solvents*: Adipic acid is not stable in alcohol. The corresponding ester is formed (Beyer, 2004).
- Henry's Law constant: 9,656e-9 hPa m³/mol 25°C (Currenta, 2009)
- log Pow*: 0.093 at pH 3.3 (BASF-Study, 1988)
- pKa: 4.34-5.44 at 18°C; 4.43-5.42 at 20°C; 4.43 at 25°C (Beilstein, 2003)

Type:

Koc

Value:

24.34 L/kg

Temp.:

25 °C

Remarks on result:

other: Calculation based on MCI method.

Type:

Koc

Value:

1.61 L/kg

Temp.:

25 °C

Remarks on result:

other: Calculation based on log Kow method

Transformation products:

not measured

Validity criteria fulfilled:

yes

Conclusions:

The estimated Koc values for adipic acid, using different accepted calculation methods are 1.61 L/kg (low Kow method) and 24.34 L/kg (MCI method). This result is acceptable for regulatory purposes.

Executive summary:

The estimated Koc values for adipic acid, using different accepted calculation methods are 1.61 L/kg (low Kow method) and 24.34 L/kg (MCI method). This result is acceptable for regulatory purposes.

Description of key information

For the mixture no data on adsorption properties are available. Adipic acid is applied for read-across approach. The estimated Koc values for adipic acid, using different accepted calculation methods are 1.61 L/kg and 24.34 L/kg (Kow/MCI method respectively). (Currenta, 2019)

Key value for chemical safety assessment

Koc at 20 °C:

1.61

Additional information

There is no adsorption / desorption test for dicarboxylic acids available.

Under environmental relevant pHs, adipic-, succinic- and glutaric acid exist predominantly in the dissociated form, based upon the individual pKa values of each cinstituent. At pH 5 to 9, the substances will be deprotonated resulting in the corresponding anion. As cationic substances in particular generally adsorb strongly, an adsorption potential of the dissociated form of the dicarboxylic acids is not expected. Nevertheless, in order to predict the mobility and fate of dicarboxylic acids in soil and sediments results from adipic acid were used, since the physico-chemical properties are very similar to the other dicarboxylic acids, and data on Koc for adipic acid are already estimated. For that purpose, the organic carbon-water partition coefficient (Koc) is calculated (Currenta, 2019) using different estimation methods following the recommendations of the Guidance document on information requirements and chemical safety assessment, chapter R.7a: Endpoint specific guidance document R.7a (ECHA, 2008). The log Kow of 0.093 was measured at pH 3.3, where the substance exists in its neutral from. This value is used as a worst-case assumption for calculation of the adsorption coefficient. Methods for estimating Koc, based on statistical relationships between Koc and the octanol/water partition coefficient (Kow) are used for calculation. Moreover, the Koc is estimated with the EPI Suite program (v. 3.20) of the U.S. Environmental Protection Agency. Here, calculations are based upon the molecule structure using the molecular connectivity method.