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Physical & Chemical properties

Water solubility

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Description of key information

The water solubility for the registered substance was calculated using the US EPA EPI-Suite model because testing was likely to be limited owing to the analytical detection limitations or to the reliability of the test method for this sparingly water-soluble UVCB substance or its components.  
The calculated water solubility values for the C18-C24 components were as follows:
C18 H38 1.137 E-4 mg/L
C20H42 1.143 E-5 to 1.172 E-5 mg/L
C22H46 1.082 E-6 mg/L
C24H50 1.069 E-7 mg/L
Hence, the calculated water solubility values for the C18 to C24 hydrogenated components of the registered substance ranged from 1.137 E-4 mg/L to 1.069 E-7 mg/L at 25ºC, indicating very low water solubility. Overall, the major C20-C22 components (i.e., as much as 95%) of the registered substance have water solubility values between 1.143 E-5 mg/L to 1.082 E-6 mg/L at 25ºC. These findings indicate that the majority of the components in the registered substance is expected to be very water-insoluble and thus, are interpreted as “water insoluble (<0.1 mg/L)”.

Key value for chemical safety assessment

Additional information

Owing to its high lipophilicity, high MW, carbon range (C18-C24) and saturated hydrocarbon characteristics, the registered substance is expected to very poorly water soluble due to its extremely hydrophilic nature. As pointed out in the ECHA Guidance R.7.A document (pg. 89), sparingly water soluble chemicals may present testing difficulties in that measurements are limited by analytical detection capabilities (1 microgram/L or ppb) and by trying to avoid the generation of any dispersed material in the saturated water solution (slow-stir technique), all of which can lead to appreciable errors and uncertainty. 

 

The slow-stir technique for poorly soluble petroleum hydrocarbon and lubricant materials [Letinski et al. Chemosphere, 48: 257 (2002)] has been applied in our laboratory and even in our experience, analytical detection limits often prove to be very challenging and is a limiting factor in trying to measure reliably the water solubility of these types of materials. The possibility of emulsion formation or generation of dispersed material in the saturated water phase as well as trying to reliably quantitate multi-component UVCB materials let alone a single pure substance are indeed challenging technically and can raise uncertainty issues.  

 

Therefore, the use of QSPR computational method (e.g., EpiSuite) to calculate the water solubility would be appropriate and allow for prediction and relative comparison of the range of water solubility for the C18-C24 components in the registered substance. In the ECHA Guidance R.7A document, EpiSuite (WSKOW) was discussed as a suitable software for calculating aqueous solubility with good performance. 

 

As summarized above, the EPI-Suite MPBPVP model gave the following calculated water solubility values for the C18-C24 components in the registered substance:

C18H38     1.137 E-4 mg/L

C20H42     1.143 E-5 to 1.172 E-5 mg/L

C22H46     1.082 E-6 mg/L

C24H50     1.069 E-7 mg/L