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Adsorption / desorption

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Description of key information

Adsorption of 1-(dimethylamino)propan-2-ol to the solid soil phase is not expected.  
    
    
    

Moreover, the substance is readily biodegradable.

Moreover, the substance is readily biodegradable.

Key value for chemical safety assessment

Additional information

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 1 -(dimethylamino)propan-2 -ol (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.

Assessment

In accordance with column 2 of REACH Annexes VIII and IX, the study does not need to be conducted if based on the physicochemical properties the substance can be expected to have a low potential for adsorption (e.g. the substance has a low octanol water partition coefficient), or the substance and its relevant degradation products decompose rapidly. The substance has an measured log Kow of -0.12 (@23°C, pH 10.9, BASF SE 2013, report no. 11L00464).

 

In order to assess the adsorption potential of the substance, the Koc value was estimated using QSAR models. According to the MCI method of the KOCWIN v2.00 module of EPI Suite v4.11, 1 -(dimethylamino)propan-2 -ol has a Koc of 1.88 (log Koc of 0.273). The MCI module is more reliable than the log Kow method of KOCWIN v2.00, which estimates the KOC based on the n-octanol/water partition coefficient (log Kow: -0.12; BASF SE 2013, report no. 11L00464). The latter method resulted in a Koc of 2.41 (log Koc of 0.382). The substance is within the applicability domain of the MCI method but not within the applicability domain of the log Kow method. These estimates are representative for uncharged molecules.

The pKa of 9.8 (measured; BASF SE, 2013; report no. 11L00464) indicates that the molecule will exist primarily as a cation in the environment. Cations generally adsorb stronger to soils containing organic carbon and clay than their neutral counterparts. 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. Under environmental conditions (pH from 5 to 8) the test substance is almost completely present in its charged form (as calculated by the formula ionised = 100/(1+10(pKa - pH)): 100% at pH 5 to 8).

Regarding the charged molecule, at pH 7 the log Koc was estimated to be 1.76 (Koc = 58 L/kg) following the method of Franco & Trapp (2008, 2009, 2010) and using the pKa of 9.8 and the estimated log Kow for the uncharged molecule of -0.12. The correction was performed for pH 5, 7 and 8, which represents 98% of the European soils.

According the calculated results it can be concluded that adsorption to the solid soil phase is not to be expected. Moreover, the substance is readily biodegradable.