Trimethylamine

Adsorption / desorption

Description of key information

The key value for chemical safety assessment was determined according to OECD Guideline 106 (von Oepen, 1991).

Adsorption of the substance to the solid soil phase is not to be expected.

Key value for chemical safety assessment

Koc at 20 °C:

6

Additional information

The soil adsorption coefficient (Koc) of the test substance was determined in a batch - equilibrium test, which was performed according to OECD Guideline 106 (von Oepen et.al., 1991). 50 mL of test solutions were added to 10 g (dry weight) of the specific soils. The soil samples were shaken for 0.5, 1, 1.5, 5, 24 and 72 hours. Then an aliquot of 1 mL of the water-phase was removed and the concentration of the substance in the aqueous phase was determined. The sorption equilibrium was reached within 16 hours. The initial concentrations used were about 15 mg/L, 5 mg/L, 0.5 mg/L and 0.15 mg/L. After reaching the equilibrium the soil samples were centrifuged, decanted, and the concentrations in the supernatant were determined by means of GC, HPLC or szintillation measurements. All samples were determined in parallel. One control and one blank were investigated additionally. After the adsorption step a two step desorption test was performed with equilibrium time of 8 hours followed by a desorption period of 16 hours. When necessary, the mass balance was determined, using a mixture of Acetonitrile/0.01M CaCl2/Acetic-Acid (80/18/2). The Freundlich constants and Koc values were calculated. For the test substance, a Koc value of 6 is reported, leading to the assumption that it will not adsorb significantly to suspended solids and sediments in water and will be highly mobile in soil .

For the uncharged molecule of trimethylamine a Koc of 7.32, as well as an logKoc of 0.86 was calculated with the help of US-EPA computer program EPIWIN v4.1 (Chemservice S.A., 2018). Based on the substance specific water solubility (4.1xE-5 mg/L) and a logKow of 0.16 the soil adsorption coefficient was estimated for trimethylamine by Lyman, W.J. (1982). The substance is not suspected to adsorb significantly to suspended solids and sediments in water due to the resulting Koc values of 4 and 29. Additionally, trimethylamine is expected to be highly mobile in soil. Further statements according amine adsorption are given by Wang, X.C. and Lee, C. (1993). The scientists state that the adsorption of amines by Montmorillonite and Kaolinite is consistent with control by electrostatic attraction as well as by van der Waals forces. The adsorption property of amines could be an important control on the distribution of these organic compounds in sediment porewaters. The adsorption can be a reversible process in clays and Flax Pont sediment.

[LogKoc: 0.778]