1,1'-iminodipropan-2-ol

Adsorption / desorption

Description of key information

Adsorption to a solid soil phase is not expected under environmentally relevant conditions. 

Additional information

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. DIPA (CAS 110-97-4) has a low log Kow of -0.79 (at 23 °C; BASF AG, 1987; see IUCLID Ch. 4.7) and is readily biodegradable according to OECD criteria (Dow Chemical Company, 1998; see IUCLID Ch. 5.2.1).

 

Although a study could be waived, the Koc was estimated using both models of KOCWIN v2.00 of EPI Suite v4.11. Using the Molecular Connectivity Index (MCI) which is regarded as more reliable compared to the log Kow method, the log Koc for the uncharged molecule was estimated to be -0.31 (Koc = 1 L/kg). Based on the measured log Pow of -0.79 (see Ch. 4.7), the log Koc was estimated at -0.38 (Koc = 0.42 L/kg) using the log Kow method. Both estimates refer to the uncharged molecule (BASF SE, 2013). However, the substance is not within the applicability domain of both of the estimation models. Therefore, these estimates may be less accurate.

 

However, the measured pKa of 9.5 (Perrin, 1964) indicates that the substance will primarily exist 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 moelcule. The pKa of MEA is 9.05 (measured; BASF AG, 1987). For the log Kow, the measured value of -0.79 (BASF AG, 1987) was used.

Regarding the charged molecule, at pH 7 the log Koc was estimated to be 1.68 (Koc = 48 L/kg) following the method of Franco & Trapp (2008, 2009, 2010) based on these data. The correction was performed for pH 5, 7, and 8, which represents 98% of the European soils. The value at pH 7 will be used as key value, i.e. for PEC and PNEC calculations.

 

There is one experimental result available for an adsorption coefficient Kd which was determined for a Canadian soil (humus-rich surface soil with approx. 16% clay, ca. 3.6% Corg) at a pH of 7.0 (Luther et al., 1998). The Kd was reported to be 2.0. Based on the given Corg content for the soil (3.6%), this value was converted according to OECD TG 106 (ECHA, 2000) to a Koc of 55.6 (log Koc = 1.745). However, as only data on one soil can be used to determine a Koc value, this data should only be used as an indicative value to support the calculated Koc.

 

In conclusion, the log Koc of the charged molecule is expected to be < 3 (pH 7, 25 °C). Therefore, significant adsorption of the substance to the solid soil phase is unlikely.