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Environmental fate & pathways

Adsorption / desorption

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Description of key information

Adsorption to the solid soil phase is not expected.

Key value for chemical safety assessment

Koc at 20 °C:

Additional information


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.

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 2-Methylimidazole (CAS 693-98-1) (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 of adsorption potential: Adsorption

 2-Methylimidazole CAS (693-98-1) has a measured log Kow of 0.22 (BASF AG, 1989, rep. no.: 103652101). In addition, the substance is readily biodegradable. Therefore, a study does not need to be provided according to Regulation (EC) 1907 (2006) Annex VIII section 9.3.1 column 2.

In order to assess the adsorption potential of the substance, the Koc value was also estimated using QSAR models. According to the MCI method of the KOCWIN v2.00 module of EPI Suite v4.11 the substance has a log Koc of 1.51. 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 (measured log Kow = 0.22, BASF AG, 1989, rep. no.: 103652101). The latter method resulted in a log Koc of 1.44. These estimates are representative for uncharged molecules; the substance is within the applicability domain of the estimation models.

At environmentally relevant conditions, CAS 693-98-1 will be present in ionized form (pKa = 7.86, see IUCLID Ch 4.21). Therefore, the adsorption coefficient was calculated according to Franco & Trapp (2008, 2009, 2010) to correct for the charged molecule at pH 5, 7, and 8. This pH range is representative for 98% of the European soils. 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 resulting Koc are at

pH 5: log Koc 2.97 (Koc: 943 L/kg)

pH 7: log Koc 2.92 (Koc: 837 L/kg)

pH 8: log Koc 2.64 (Koc: 432 L/kg)

It can be concluded that adsorption to the solid soil phase is not expected under environmentally relevant conditions.