N-(2-aminoethyl)-N'-[3-(trimethoxysilyl)propyl]ethylenediamine

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption: screening

Remarks:

adsorption

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

the study does not need to be conducted because the substance has a low octanol water partition coefficient and the adsorption potential of this substance is related to this parameter

Description of key information

N-(2-aminoethyl)-N'-[3-(trihydroxysilyl)propyl]ethylenediamine (silanol hydrolysis product): log Koc = 0.26 at pH 7 (QSAR)

Key value for chemical safety assessment

Koc at 20 °C:

1.81

Additional information

N-(2-aminoethyl)-N’-[3-(trimethoxysilyl)propyl]ethylenediamine (CAS 35141-30-1) degrades rapidly in water via hydrolysis and forms N-(2-aminoethyl)-N'-[3-(trihydroxysilyl)propyl]ethylenediamine and methanol (half-life = 4.3 h at 25°C and pH 7). The silanol hydrolysis product has a very low octanol–water partition coefficient (-3.9 based on QSAR) and thus low potential for adsorption. The other hydrolysis product, methanol has also negligible adsorptive properties (OECD, 2004). Thus in accordance with Column 2 of REACH Annex VIII, the adsorption/desorption screening test does not need to be conducted.

For the purposes of the chemical safety assessment further information on the adsorption behavior of the silanol hydrolysis product N-(2-aminoethyl)-N'-[3-(trihydroxysilyl)propyl]ethylenediamine (since the parent compound is not stable in the environment), was collected using an appropriate calculation method.

Considering the ionization properties of N-(2-aminoethyl)-N'-[3-(trihydroxysilyl)propyl]ethylenediamine, the adsorption potential has been calculated using Franco and Trapp ‘s expressions (2008) on estimation of the organic carbon-water partitioning coefficient of ionisable organic substances. The log Kow, the pH as well as the pKa values were used as input parameters. The pka values were determined using the software SPARC v4.6 (pKa calculator). The macro pKa value within the environmental relevant range was calculated to be 4.29. This value was used as an input parameter for the calculation of the Koc coefficient.  

The following equation was used for Koc calculation as suggested by the authors:

Koc =Fn * 10 ^ (0.37*logPn+1.70) + Fion * 10 ^ (pKa^0.65*f^0.14)

Where:

Fn = 1/(1+10(pH-pKa))

Pn: Kow of the neutral molecule

pKa: 4.29 (SPARC v4.6)

Fion = 1- Fn

f: Ratio of concentration in octanol to total concentration: Kow (overall)/(Kow (overall) + 1)

The log Koc was calculated to be 0.54 at pH 4; 0.26 at pH 7 and 0.26 at pH 9. These values indicate the low adsorption potential of the substance to organic carbons in soil. According to the Guidance on Information Requirements and Chemical Safety Assessment, Chapter R.7.1.8.5 the log D value for the ionized molecule determined around the default pH of 7 is considered more relevant for chemical safety assessment. On this basis the calculated log Koc of 0.26 (Koc = 1.81 at pH 7) has been used for the chemical safety assessment.

 

Reference:

Franco A. & Trapp S., 2008: Estimation of the soil-water partition coefficient normalized to organic carbon for ionizable organic chemicals. Environmental Toxicology and Chemistry, Vol. 27, No. 10, pp. 1995–2004.

[LogKoc: 0.258]