Oxirane, reaction products with ammonia, distn. residues

Adsorption / desorption

Description of key information

For the main constituents of AMIX TE (CAS 68953-70-8), adsorption to the solid soil phase is to be expected.

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 AMIX TE (CAS 68953 -70 -8) (Q)SAR results for the three main components of the UVCB 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

A study on the adsorption potential of AMIX TE does not need to be conducted because AMIX TE is readily biodegradable according to OECD criteria (BASFAG, 1996; project no. 95/0675/21/1). In addition, a study is also not required as the main constituents of AMIX TE have a low log Kow (see IUCLID Ch. 4.7).

 - Triethanolamine (CAS 102-71-6; typical concentration: 86%): log Kow = -2.3 at pH 7 and 25 °C; log Kow = 1.34 at pH 9.5 and 25 °C (measured; BASF AG, 1995; project no. 90P03095.03)

- 2,2'-{[2-(2-hydroxyethoxy)ethyl]imino}diethanol (CAS 17626-34-5; typical conc.: 6%): log Kow = -2.75 at 25 °C (calculated, KOWWIN v1.68, see IUCLID Ch. 4.7)

- N,N,N',N'-Tetra-(2-hydroxyethyl)-bis 2,2'-aminoethylether (CAS 55468 -09 -2; typical conc.: 7%): log Kow = -4.03 at 25°C (calc., KOWWIN v1.68, see IUCLID Ch. 4.7)

In order to derive a value for the adsorption potential of the constituents, the Koc values were estimated using QSAR models. The KOCWIN v2.00 submodel of EPI Suite v4.11 (US EPA, 2012) provides two methods for the derivation of the log Koc: MCI and log Kow. The MCI method is more reliable than the log Kow method of KOCWIN v2.00, which estimates the KOC based on the n-octanol/water partition coefficient. These estimates are representative for uncharged molecules. As the number of fragments were exceeded by all three main constituents, none of the substances was within the applicability domain of KOCWIN.

At environmentally relevant conditions, the main constituents will be present in ionised form (pKa = 7.05 to 7.86; see IUCLID Ch. 4.21). Therefore, the adsorption coefficients of the three main constituents were 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 log Koc values range from 0.74 to 3.60 at pH 7.

The individual log Koc values are listed below: 

CAS no.	Typical conc.	KOCWIN v2.00: log Koc (uncharged molecule)			Franco & Trapp (2008/2009/2010): log Koc
		MCI method	KOW method	Applicability domain	pH 5	pH 7	pH 8
102-71-6	86%	-0.148	0.778	not in AD	3.65	3.60	3.30
55468-09-2	7%	1.00	-2.34	not in AD	0.78	0.74	0.53
17626-34-5	6%	1.00	-1.78	not in AD	1.32	1.12	0.81

While the log Koc for the charged molecule of triethanolamine (CAS 102-71-6) indicates that adsorption to the solid soil phase is to be expected, the other two main constituents do not adsorb. Based on a pH-corrected Koc calculated for the charged substance, adsorption to the solid soil phase is to be expected for the main constituent CAS 102-71-6 (typical conc. 86%), while adsorption of the other two main constituents (CAS 17626-34-5, 55468-09-2) is not to be expected at pH 7.