Registration Dossier
Registration Dossier
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EC number: 269-616-7 | CAS number: 68307-94-8
Adsorption / desorption
Administrative data
Link to relevant study record(s)
Description of key information
The estimated adsorption coefficient (log10 Koc) values ranged from log10 Koc 2.53 to 7.49 (Kow method) and 2.27 to 7.54 (MCI method).
Key value for chemical safety assessment
Additional information
No determination of the adsorption coefficient was possible by the HPLC screening method, Method C19 Adsorption Coefficient of Commission Regulation (EC) No 440/2008 of 30 May 2008 and Method 121 of the OECD Guidelines for Testing of Chemicals, 22 January 2001.
The adsorption coefficient of each of the main test item components was estimated using a computer-based atom fragment contribution method, KOCWIN, version 2.00 (September 2010) © 2000-2008 US Environmental Protection Agency. The estimated adsorption coefficient (log10Koc) values are presented in the following table:
Component |
Estimated log10Koc |
|
MCI method |
Kow method |
|
C8 monoester |
2.27 |
2.53 |
C10 monoester |
2.79 |
3.08 |
C6/C8 diester |
3.86 |
3.93 |
C8/C8 diester |
4.38 |
4.47 |
C8/C10 diester |
4.90 |
5.01 |
C10/C10 diester |
5.42 |
5.55 |
C6/C8/C8 triester |
5.98 |
5.86 |
C8/C8/C8 triester |
6.50 |
6.40 |
C8/C8/C10 triester |
7.02 |
6.94 |
C8/C10/C10 triester |
7.54 |
7.49 |
Discussion
The test item is a mixture of phosphoric acid alkyl esters and since the HPLC screening method is not suitable for organic acids, estimates of the adsorption coefficients were obtained using the specialised predictive software.
The dissociation constants of the acidic functional groups were estimated to be in the range of 1.50 to 6.47 (see Dissociation Constants in Water). Subsequently, as values of dissociation constants were less than 4.5; 10% or greater of the unionised form of the test item cannot be achieved within the environmentally relevant pH range of 5.5 to 7.5. Therefore as the unionised form of the test item is not of environmental relevance, and the HPLC estimation method is invalid for the ionised form of the acidic functional group, the specialised predictive software PCKOCWIN, version 2.00 (September 2010) © 2000 - 2008, U.S. Environmental Protection Agency was used.
The software cautioned that the adsorption coefficient of the test item may be sensitive to pH. However, based on available dissociation constant values, the test item would retain an anionic form over the whole pH range applicable to environmental assessment (5.5 to 7.5); hence the application of a negative fragment constant to the acidic functional group in the adsorption coefficient estimate, indicating that the anionic group will potentially increase the mobility of the test item in the soil/water system.
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