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EC number: 939-513-8 | CAS number: -
Partition coefficient
Administrative data
Link to relevant study record(s)
- Endpoint:
- partition coefficient
- Type of information:
- (Q)SAR
- Adequacy of study:
- key study
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- results derived from a valid (Q)SAR model and falling into its applicability domain, with limited documentation / justification
- Remarks:
- This is an accepted calculation method supported by a limited amount of additional validation.
- Justification for type of information:
- See attached QMRF/QPRF
- Principles of method if other than guideline:
- Method: other (calculated): Estimation by KOWWIN program, USEPA/Syracuse Research, v1.40 (see attached QMRF and QPRF).
- GLP compliance:
- no
- Partition coefficient type:
- octanol-water
- Key result
- Type:
- log Pow
- Partition coefficient:
- -4
- Temp.:
- 20 °C
- Remarks on result:
- other: For the linear form
- Conclusions:
- A predicted log Kow of -4 ± 1 was determined for HEBMP-H using a relevant estimation method. The result is considered reliable.
- Endpoint:
- partition coefficient
- Type of information:
- (Q)SAR
- Adequacy of study:
- key study
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- results derived from a valid (Q)SAR model and falling into its applicability domain, with limited documentation / justification
- Remarks:
- This is an accepted calculation method supported by a limited amount of additional validation.
- Justification for type of information:
- See attached QMRF/QPRF
- Principles of method if other than guideline:
- Method: other (calculated): Estimation by KOWWIN program, USEPA/Syracuse Research, v1.40 (see attached QMRF and QPRF).
- GLP compliance:
- no
- Partition coefficient type:
- octanol-water
- Key result
- Type:
- log Pow
- Partition coefficient:
- -3.4
- Temp.:
- 20 °C
- Remarks on result:
- other: For the cyclic form
- Conclusions:
- A predicted log Kow of -3.4 ± 1 was determined for HEBMP-cyclic using a relevant estimation method. The result is considered reliable.
Referenceopen allclose all
Description of key information
log Kow [HEBMP-H]: -4 (QSAR)
log Kow [HEBMP-H
cyclic]: -3.4 (QSAR)
When adjusted to neutral pH range:
log Kow [linear HEBMP-H]: ≤-4
log Kow [EBMP-H
cyclic]: ≤-4
Key value for chemical safety assessment
- Log Kow (Log Pow):
- -4
- at the temperature of:
- 20 °C
Additional information
HEBMP-xNa is freely soluble in water and, therefore, the HEBMP anion is fully dissociated from its potassium cations when in solution. The l-HEBMP anion has four P-OH groups and the c-HEBMP has three P-OH groups that can be ionised. They lose a hydrogen to form negatively charged groups (P-O-). As the pH increases, the number of ionised groups increases. Under any given conditions, the degree of ionisation of the HEBMP species is determined by the pH of the solution. At a specific pH, the degree of ionisation is the same regardless of whether the starting material was HEBMP-xNa, HEBMP-H or another salt of HEBMP.
Therefore, the log Kow predicted for HEBMP-H is directly relevant for HEBMP-xNa. The log Kow for an ionising substance will vary with pH as the ionised species will have a greater hydrophilicity and lower log Kow than the neutral species.
The log Kow of HEBMP-xNa has been read-across from the parent acid. Predicted log Kow values of -4±1 and -3.4±1 at 20°C were determined for linear HEBMP-H and cyclic HEBMP-H respectively using an appropriate QSAR estimation method. A predicted log Kow value below -4 was reported as -4. The results are considered reliable and are selected as key studies. The prediction is for the acid form. As the pH is increased to neutral, ionisation of the phosphonate groups occurs, decreasing the log Kow value. Therefore, the estimated log Kow for the unionised form was corrected for ionisation using the equation CORR = 1/1 +10A(pH-pKa) [where A = 1 for acids, -1 for bases; pH = pH-value of the environment; pKa = acid/base dissociation constant].
For environmental exposure assessment, it is appropriate to refer to the value under neutral conditions which is log Kow -4 for both constituents.
For further details of the speciation of HEBMP see PFA 2020.
Reference
PFA 2020: HEBMP speciation at pH relevant to Ecotoxicology and Toxicology, Reference: PFA.224.605.001, November 2020.
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