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EC number: 204-376-9 | CAS number: 120-20-7
Adsorption / desorption
Administrative data
Link to relevant study record(s)
Description of key information
It can be concluded that adsorption of 3,4-Dimethoxyphenethylamine (CAS 120-20-7) to the solid soil phase is not expected under environmentally relevant conditions.
Key value for chemical safety assessment
- Koc at 20 °C:
- 119
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.
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 3,4 - Dimethoxyphenethylamine (CAS 120 -20 -7) (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 Annex IX the study does not need to be conducted since the substance is readily biodegradable and it has a log Kow less or equal than 3. The substance (CAS 120-20-7) has a log Kow of -1.15 (measured at pH 7, 25 °C; BASF AG, 1991, report no. 91P04664) and it is readily biodegradable according OECD criteria (see IUCLID Ch. 5.2.1)
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 3,4-Dimethoxyphenethylamine (CAS 120-20-7) has a log Koc of 2.32. 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: -1.15; charged molecule, BASF AG, 91P04664, 1991). The latter method resulted in a log Koc of 0.38. These estimates are representative for uncharged molecules; the substance is within the applicability domain of the estimation models.
At environmentally relevant conditions,3,4-Dimethoxyphenethylamine(CAS 120-20-7) will be present in ionized form (pKa= 10.46 @ 20°C, HSDB 2010, 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 at pH 5-8 is 119 L/kg (log Koc: 2.07).
It can be concluded that adsorption to the solid soil phase is not expected under environmentally relevant conditions.
[LogKoc: 2.07]
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