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Adsorption / desorption

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adsorption / desorption: screening
Data waiving:
study technically not feasible
Justification for data waiving:
Justification for type of information:

Experimental assessment of the adsorption coefficient on soils and sludges was not feasible for this test item by either:
- the HPLC estimation method, as detailed in Method C19 Adsorption Coefficient of Commission Regulation (EC) No 440/2008 and Method 121 of the OECD Guidelines for Testing of Chemicals, or
- the batch equilibrium method, as detailed in Method C18 Adsorption Coefficient of Commission Regulation (EC) No 440/2008 of 30 May 2008 and Method 106 of the OECD Guidelines for Testing of Chemicals.
Furthermore, its chemical class of a salt prevented the use of alternative estimation methods such as the predictive software KOCWIN, version 2.00, © 2000 US EPA, or the use of Quantitative Structure Activity Relationship.

Due to the test item being a salt, which may lead to secondary interactions with the HPLC column stationary phase other than partitioning, and critically the absence of any appropriate reference standards with which to generate a valid calibration curve, the HPLC estimation method was not considered a suitable or valid option for this test item.

For the batch equilibrium method, both method guidelines limit the maximum working concentration of the sample solutions to that of the water solubility of the test item. The calculated water solubility of Solvent Black 46 was less than 1 x 10^-5 g/l (see section 4.8 of the dossier). However due to limitations of the analytical method and the presence of trace levels of starting components remaining as impurities, this still may represent a significant overestimation of the true water solubility. Such concentrations are not feasible for the batch equilibrium method.

Further to this, EC Method C18 and OECD Method 106 state that the procedure may not be suitable for items with a partition coefficient value greater than 1 x 10^4, i.e. log Kow > 4.0, and in such cases estimation techniques may be more applicable. This is since suitable methodology is not available to generate homogeneous soil to solution mixtures at a suitable ratio which would retain sufficient test item in the aqueous phase to allow analytical quantification. The partition coefficient of the test item has been estimated to be a log Kow value of greater than 5.7 using its concentration in octanol-1 and water separately. Therefore, this value is considered underestimated giving an overestimation of the test item water solubility concentration.

Description of key information

No experimental study available, since the study was technically not feasible.

Key value for chemical safety assessment

Koc at 20 °C:
52 200

Additional information

The Log Kow value of 5.7 was used, in association with the chemical class „predominantly hydrophobic“ as implemented in the EUSES software version 2.1.1 to calculated the Koc value of 52200 L/kg (logKoc=4.7) selected to run the CSA.

Given the high calculated log Koc value, consistent with the extremely low water solubility and high partition coefficient characteristics; it indicated that the substance would adsorb rapidly to soil or sludge, showing little or no mobility (according to P.J. McCall et al., 1981)1 showing little or no mobility, and therefore no presence in the aquatic compartment of the environment.

1 McCall P.J., Laskowski D.A., Swann R.L., and Dishburger H.J., (1981), “Measurement of sorption coefficients of organic chemicals and their use, in environmental fate analysis”, in Test Protocols for Environmental Fate and Movement of Toxicants. Proceedings of AOAC Symposium, AOAC, washington DC.

McCall classification scheme of mobility

 Koc range  Class of mobility
 0 - 50  Very high
 50 - 150  High
 150 - 500  Medium
 500 - 2000  Low
 2000 - 5000  Slightly
 > 5000  Immobile

[LogKoc: 4.7]