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Adsorption / desorption

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Description of key information

Adsorption of the major hydrolysis product bis(2-ethylhexyl)amine to solid phase is expected. The other degradation products are expected to be of higher mobility in soil.

Key value for chemical safety assessment

Additional information

Parent substance EC 401 -280 -0

Experimental data on the test substance EC 401 -280 -0 are available. However, as immediate hydrolysis was not considered in the test, the results of this test are not used for further assessment and disregarded. The substance EC 401-280-0 hydrolyses in contact with water immediately. Therefore the hydrolysis products need to be considered.

Hydrolysis products:

bis(2 -ethylhexyl)amine

The adsorption coefficient was measured according to the HPLC method (OECD 121). At pH 9.0, the HPLC retention time of the substance was greater than those of the reference substances. Therefore, the log Koc was determined as > 5.63. At pH 7.0, a log Koc of 5.5 was determined for the charged molecule (BASF SE, 2013, study no. 11L00538).

In addition, the Koc was estimated using both models of KOCWIN v2.00 of EPI Suite v4.10 (BASF SE, 2013). 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 4.49 (Koc = 30880 L/kg). Based on the measured log Pow of 7.3 (25 °C, pH 7.5; OXEA 2010, report no. AN-ASB 0496), the log Koc was estimated at 4.92 (Koc = 83060 L/kg) using the log Kow method. Both estimates refer to the uncharged molecule (pKa 10.59).

The pKa of 10.6 indicates that the molecule will exist primarily as a cation in the environment and cations generally adsorb stronger to soils containing organic carbon and clay than their neutral counterparts. Hence, the KOCWIN model may underestimate adsorption to organic carbon since it does not consider the ionic structure of the molecule. Under environmental conditions (pH from 5 to 8) the test substance is almost completely present in its charged form (as calculated by the formula% ionised = 100/(1+10(pKa - pH)): 100% at pH 5 to 8).

Regarding the charged molecule, at pH 7 the log Koc was estimated to be 4.64 (Koc = 43254 L/kg) following the method of Franco & Trapp (2008, 2009, 2010) and using the pKa of 10.59 and the estimated log Kow for the uncharged molecule of 6.56. The correction was performed for pH 5, 7, and 8, which represents 98% of the European soils.

Due to the uncertainty of the measured value according to OECD 121, the calculated value for pH 7 using the method of Franco & Trapp (2008, 2009, 2010) will be used as key value, i.e. for PEC and PNEC calculations.

According to a weight-of-evidence approach, adsorption to solid soil phase is to be expected.

1H-1,2,4 -triazole

Data show that the KOC of triazole in different soils ranges from 43 to 120. The maximum KOC of 120 and the average KOC of 112 indicate indicate mobility in soil. (ECHA disseminated REACH dossier, 2014)

formaldehyde CAS 50 -00 -0

The calculated Log Koc using the formula for nonhydrophics as given in TGD part 3 (2003), resulted in a value of 1.202, suggesting moderate to high mobility of formaldehyde in soil (BASF SE, 2008).