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Environmental fate & pathways

Adsorption / desorption

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Description of key information

Based on the available experimental data of the structurally analogous substance TETA, adsorption to solid soil phase is indicated (geometric mean log Koc = 3.49; Koc = 3090.3 L/kg; Akzo Nobel, 2010). In terms of a worst-case approach, these data were selected for the assessment (PNEC derivation).

However, since 3,3'-iminodi(propylamine) is readily biodegradable and has a low log Kow of -1.25, it is not expected to adsorb to the solid phase.

Key value for chemical safety assessment

Additional information

In accordance with column 2 of REACH Annexes VIII and IX, a 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. 3,3'-iminodi(propylamine) (CAS 56 -18 -8) has a measured log Kow of -1.25 (BASF AG 1989; BRU 89.022; @25°C) and is readily biodegradable (according to OECD criteria; BASF SE 2011; 22G0696/05G003).

Considering the adsorption potential of 3,3'-iminodi(propylamine), no experimental data are available. Therefore, the assessment is based on a weight-of-evidence approach by read-across data for the structurally similar substance TETA (CAS 112-24-3), as well as by calculated data for 3,3'-iminodi(propylamine) itself:

The adsorption of the structural analogue TETA (CAS 112-24-3) was determined in a GLP guideline study according to OECD 106 (Akzo Nobel, 2010). The log Koc was measured to be in a range of 3.2 to 3.7 (at 22 °C) depending on type of soil (geometric mean log Koc = 3.49; Koc = 3090.3 L/kg; Akzo Nobel, 2010), indicating adsorption to be expected. In terms of a worst-case approach, these data were selected for the assessment (PNEC derivation).

In addition, the Koc value was estimated using QSAR models. According to the MCI method of the KOCWIN v2.00 module of EPI Suite v4.11, 3,3'-iminodi(propylamine) has a Koc of 112.2 L/kg and a log Koc of 2.05. 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 of -1.25 @25°C, BASF AG 1989, report no. BRU 89.022). The latter method resulted in a Koc of 1.40 L/kg and a log Koc of 0.147. These estimates are representative for the uncharged molecule.

At environmentally relevant conditions, however, the substance will be present in its ionised form (pKa = 10.69; calculated with SPARC On-Line Calculator (http://archemcalc.com/sparc-web/calc). 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 resulting Koc value was 12.1 at pH 7. 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.

 

Conclusion:

Based on the available experimental data of the structurally analogous substance TETA, adsorption to solid soil phase is indicated (geometric mean log Koc = 3.49; Koc = 3090.3 L/kg; Akzo Nobel, 2010). In terms of a worst-case approach, these data were selected for the assessment (PNEC derivation).

However, since 3,3'-iminodi(propylamine) is readily biodegradable and has a low log Kow of -1.25, it is not expected to adsorb to the solid phase. The calculated data for 3,3'-iminodi(propylamine) further support this conclusion.