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Environmental fate & pathways

Adsorption / desorption

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Description of key information

Adsorption to solid soil phase is expected.

Key value for chemical safety assessment

Koc at 20 °C:
10 000

Additional information

Adsorption/desorption screening with HPLC cannot technically be performed on the members of the Stilbene Fluorescent Whitening Agents category, because of their interaction with silica.

Traditional estimation methods rely upon the octanol/water partition coefficient or related parameters, but the first-order molecular connectivity index (MCI) has been used successfully to predict Koc values for hydrophobic organic compounds (Sabljic, 1984, 1987; Bahnick and Doucette, 1988). The original KOCWIN program (PCKOC) used MCI and a series of group contribution factors to predict Koc (Meylan et al., 1992).  This group contribution method was shown to outperform traditional estimation methods based on octanol/water partition coefficients and water solubility.

Two adsorption studies for the assessment of the adsorption potential of the substances belonging to the Stilbene Fluorescent Whitening Agents category are available. They have been performed on CAS 16090-02-1 (morpholino derivative, disulphonate) and 16470-24-9 (the analogous dihydroxyethylamino disulphonated). The two tested substances are different in tems of solublity and log Kow, but their adsorption potential to soil doesn't change sensibly, demonstrating that the property is more related to the whole structure, geometry and organic functional groups; both studies demonstrate that the substances belonging to this category possess a high adsorption potential all along the category which indicates that the tested substances bind to soils and sediments.

Considering the adsorption behaviour observed during the Zahn Wellens test for CAS 16470 -24 -9 and CAS 689719-49 -3 and their similarity in fuctional groups it can be assumed that they will have a very similar behaviour in the adsorption/desorption properties and the result of logKoc = 4 obtained for 16470 -24 -9 can be taken as key result for 68719 -49 -3 also

[LogKoc: 4.0]

[LogKoc: 4.0]