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Environmental fate & pathways

Adsorption / desorption

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Description of key information

The estimated Koc values for homologous components of this UVCB substance is in the range of 10 to 491 L/kg for the lowest (least sorptive) and highest (most sorptive) molecular weight homologues which gives a log Koc range of 1 to 2.7. The components of this UVCB substance can be regarded as having low affinity for adsorption to soils and activated sludge biosolids (West, 2010).

Key value for chemical safety assessment

Additional information

The KOCWIN software is shown to produce estimated log Koc values which are typically within 0.3 log units of measured values for a set of amine- and alcohol-bearing substances which are expected to have log Koc values bracketing that of the test substance. Because the software training set includes measured Koc values for several aliphatic and aromatic amine substances, it is expected to provide accurate predictions of adsorption for amine-initiated NLP polyols, which may adsorb to soil by a combination of cation-exchange and hydrophobic partitioning mechanisms. These results are therefore expected to provide a more realistic estimation of adsorption potential than the HPLC estimation method, which may be confounded by the surface-activity of the test substance components and lack of relevant reference substances (i.e., aromatic, alcohols, ethers, amines) employed in the OECD 121 guideline.

 Adsorption/Desorption was investigated using the OECD 121 method, and results indicated Koc <17.8 to > 427000 and Log Koc <1.25 to >5.63 over the pH range of 5.5 to 7.5. These results indicate an unexpected high affinity for adsorption of the test substance components, which is contradictory to their very high water solubility, and low log Kow values. Furthermore, because the HPLC method does not account for the cation-exchange mode of adsorption, it may not correctly predict the adsorption of the test substance components which posses cationic amino-groups.