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Adsorption / desorption

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Description of key information

Based on a weight-of-evidence approach, adsorption of the N3/N4-Amine mix (CAS 68909-99-9) to solid soil phase is not expected under environmentally relevant conditions.

Key value for chemical safety assessment

Additional information

The assessment of the adsorption potential of the mixture N3/N4-Amine (CAS 68909-99-9) is based on experimental data for the component Ethylenediamine (CAS 107-15-3; fraction: 5 - 15 %, w/w) and additional (Q)SAR estimations, using the MCI method as well as the Kow method of the KOCWIN v2.00 module from SRC EPI Suite v4.11, for the following major constituents of the mixture:

 

- (CAS 13531-52-7) 1,3-Propanediamine, N1-(2 -aminoethyl)- (fraction: >25 - <35%, w/w)       

- (CAS 10563-26-5) 1,3-Propanediamine, N,N''-1,2-ethanediylbis- (fraction: >45 - <55%, w/w)

- (CAS 58214-71-4) 1,3-Propanediamine, N,N''-(iminodi-2,1-ethanediyl)bis- (fraction: 0 - 8%, w/w)

 

In addition, estimation data (KOCWIN v2.0; EPISuite v 4.11) for the structurally similar component 1,2-Ethanediamine, N,N'-bis(2-aminoethyl)- (CAS 112-24-3) are available.

 

The EPISuite estimates are representative for the uncharged molecules of the substances. However, the pKa values of the read-across substances (see IUCLID chapter 4.21) indicate that these molecules will primarily exist as cations in the environment. As cations generally adsorb stronger to soils containing organic carbon and clay than their neutral counterparts, the KOCWIN model may underestimate adsorption to organic carbon since it does not consider the ionic structure of the molecule. Franco & Trapp (2008, 2009, 2010) have developed a method to take this effect into consideration when assessing the adsorption potential. The model is not yet validated; in addition, the applicability domain is not clearly defined. Nevertheless, the Koc values of the Franco & Trapp method give a good indication on the adsorption potential of a substance depending on the pH conditions of soil. The method is based on the dissociation constant pKa and the log Kow for the uncharged molecule.

The calculated log KOC values are listed in the table below:

 

CAS#

KOCWIN v2.00

Franco & Trapp (@ pH 7)

MCI method

(uncharged)

KOW method (uncharged)

Within applicability domain

13531-52-7

1.79

-0.09

yes

0.96

10563-26-5

2.41

-0.06

no

1.0

58214-71-4

2.76

-0.455

no

0.8

112-24-3

1.89

-0.67

no

0.7

 

The log Koc value for the component ethylenediamine (CAS 107-15-3) was experimentally determined in an OECD 106 guideline study to be in a range of 3.32 to 3.85 (at pH 11; Dow Chemical Company, 1991).

 

Conclusion:

The measured data for ethylenediamine (CAS 107-15-3) indicate adsorption of this component to the solid soil phase; the fraction of ethylenediamine is between > 5 and < 15% (w/w). However, as the log Koc values for all other constituents, representing a main fraction of at least > 70% (w/w), were consistently calculated to be lower than 3, adsorption of the N3/N4-Amine mix (CAS 68909-99-9) to solid soil phase is concluded to be not expected under environmentally relevant conditions. The Koc value of the major constituent CAS 10563-26-5 1,3-Propanediamine, N,N''-1,2-ethanediylbis- (fraction: >45 - <55%, w/w) was used for PNEC derivation.

 

QSAR-disclaimer

In Article 13 of Regulation (EC) No 1907/2006, it is laid down that information on intrinsic properties of substances may be generated by means other than tests, provided that the conditions set out in Annex XI (of the same Regulation) are met. Furthermore according to Article 25 of the same Regulation testing on vertebrate animals shall be undertaken only as a last resort.

 

According to Annex XI of Regulation (EC) No 1907/2006 (Q)SAR results can be used if (1) the scientific validity of the (Q)SAR model has been established, (2) the substance falls within the applicability domain of the (Q)SAR model, (3) the results are adequate for the purpose of classification and labeling and/or risk assessment and (4) adequate and reliable documentation of the applied method is provided.

 

For the assessment of the mixture N3/N4-Amine (Q)SAR results were used for the estimation of the adsorption potential. The criteria listed in Annex XI of Regulation (EC) No 1907/2006 are considered to be adequately fulfilled and therefore the endpoint(s) sufficiently covered and suitable for risk assessment.

 

Therefore, further experimental studies on the adsorption potential are not provided.