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Environmental fate & pathways

Adsorption / desorption

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Description of key information

The adsorption coefficient of the test material was determined to be 1.9 x 10⁵. The log Koc of the test material was determined to be 5.3.

Key value for chemical safety assessment

Koc at 20 °C:
190 000

Additional information

There are two studies available to address this endpoint, one key and one supporting.

 

The key study, the adsorption coefficient of the test material was investigated using the HPLC method in a study which was performed under GLP conditions and in accordance with the standardised guidelines OECD 121 and EU Method C.19. The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).

Following calculation of the pKa values of the test material, the UPLC analysis was performed at neutral pH. Solutions of reference materials with known log Koc values based on soil adsorption data and the test material were analysed. The capacity factor (k') of each compound was calculated from its retention time. The log k’ values of the reference materials were plotted against the known log Koc values. A linear regression program was used to calculate the calibration curve. Linear regression analysis was performed using the least squares method. The coefficient of correlation (r) was calculated. The log Koc value for the test material was calculated by substituting its mean log k’ in the calibration curve. The value of log Koc obtained from duplicate measurements was within ± 0.25 log units.

Under the conditions of the study, the adsorption coefficient of the test material was determined to be 1.9 x 10⁵. The log Koc of the test material was determined to be 5.3. The determination was carried out at neutral pH; the column temperature was 35 °C.

In the supporting study, the adsorption coefficient (Koc) of the test material was estimated using the KOCWIN model v2.00 (EPI Suite v4.11). The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).

The Soil Adsorption Coefficient Program (KOCWIN) estimates the soil adsorption coefficient (Koc) of organic compounds. Koc can be defined as "the ratio of the amount of chemical adsorbed per unit weight of organic carbon (oc) in the soil or sediment to the concentration of the chemical in solution at equilibrium" (Lyman, 1990).

PCKOCWIN (version 2) estimates Koc with two separate estimation methodologies: estimation using first-order Molecular Connectivity Index (MCI); and estimation using log Kow (octanol-water partition coefficient).

Sufficient information on the model training set is available to evaluate the applicability of the model to this substance. The molecular weight of the test material is within the training set range.

The estimated Log Koc was 4.800 using the MCI Method and 4.444 using the Kow method.

[LogKoc: 5.3]