Eldew APS-307

Water solubility

Description of key information

The water solubility of the test material was determined to be less than 0.1 mg/L of solution at 20.0 ± 0.5 °C, using a short-term flask method based on Method A6 Water Solubility of Council Regulation (EC) No 440/2008 of 30 May 2008. Using a fragment constant methodology, the water solubility of the individual components of the test material were estimated to be less than 0.000000001 g/L.

Additional information

Discussion:

Whereas the preliminary test short-term assessment test was a clear solution containing solid, excess un-dissolved test material when removed from the 20°C static water bath for analysis (and subsequently was demonstrated to contain less than 1 x l0^-4 g/L of solution), the definitive test samples were observed to contain test material in a dispersion/suspension throughout the solution. The definitive test solutions were centrifuged prior to analysis and were seemingly clear at the time of analysis, however the final analytical results where significantly higher than anticipated. It was therefore believed that the definitive test solutions contained a degree of contamination in the form of a micro-emulsion at the time of analysis causing a systematic overestimation of the water solubility of the test material. Surface active properties were observed within the definitive test samples, and this was consistent with the proposed chemical structure for the test material, which contains distinct polar and non-polar regions. The negligible solubility of the test material was further supported by the high partition coefficient result and the validated computer estimation of water solubility, which resulted in values many magnitudes below that achievable analytically. Filtration of the solutions was not performed prior to analysis due to potential strippinglpartitioning of the extremely hydrophobic test material onto the filter membranes andlor filter bodies. Also based on the computer estimations of water solubility, even when using a significant co-solvent content, it may not be possible to prepare true solutions of test material at a concentration that could be monitored analytically. Therefore, it would be extremely difficult to distinguish between mechanical and adsorptive processes if a significant reduction in test material concentration was obtained for filtered procedural recoveries. Finally, in cases of colloidal (<0.2 µm ) emulsions, filtration once more may fail to completely remove all excess, undissolved test material suspended in the solutions. The preliminary water solubility test indicated that the column elution method should have been performed as the solubility was less than 1 x 10^-2 g/L. However, due to the physical nature of the test material, it was not possible to use this method; experience has shown that soft, waxy test materials coated onto glass beads cause these beads to compact andlor adhere together, forming a plug within the column and thus preventing water circulation.

Conclusion

The water solubility of the test material was determined to be less than 1.0 x l0^-4 g/L of solution at 20.0 ± 0.5 °C, using a short-term flask method based on Method A6 Water Solubility of Council Regulation (EC) No 440/2008 of 30 May 2008. Using the non-amended procedure, solubility results in the range 1.05 x l0^-4 to 2.26 x 10^-4 g/L of solution at 20.0 ± 0.5 °C were obtained. However, based on structural information supplied by the Sponsor and other physico-chemical properties of the test material, specifically the extremely high partition coefficient result, these values were considered to systematically overestimate the true solubility of the test material. The cause for this error was attributed to surface active properties observed for the test material during the extended saturation shaking periods required by EC Method A6 preventing complete sample clean-up prior to analysis. The essential insolubility of the test material was also fully supported by the specialised predictive sohare, WSKOWWIN, version 1.41, 2000 US Environmental Protection Agency. Using a fragment constant methodology, the water solubility of the individual components of the test material were estimated to be significantly below 1 ppt (< 1 x 10^-9 g/L of solution).