[[(phosphonomethyl)imino]bis[hexamethylenenitrilobis(methylene)]]tetrakisphosphonic acid

Partition coefficient

Link to relevant study record(s)

Reference

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 adequate and reliable 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 and 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

pH:

< 1

Remarks on result:

other: The log Kow of the dissociated form would also be expected to be extremely low.

Conclusions:

A predicted log Kow limit value of -4 was determined for the substance using a relevant estimation method. The result is considered reliable.

Description of key information

log K_ow (BHMT-H): -4 (QSAR)

Key value for chemical safety assessment

Log Kow (Log Pow):

-4

at the temperature of:

20 °C

Additional information

A predicted log K_ow of -4 at 20°C was determined for the substance uisng a validated QSAR estimation method. The result is considered reliable and selected as key study. A measured limit log K_ow value of <0 was determined for the substance using OECD 117 and in compliance with GLP. However, no information on pH and temperature was reported. The predicted log K_ow represent that of the unionised species.

BHMT-H and its sodium and potassium salts are freely soluble in water. The BHMT anion can be considered fully dissociated from its sodium or potassium cations when in dilute solution. Under any given conditions, the degree of ionisation of the BHMT 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 BHMT-H or a salt of BHMT.

The log K_ow for an ionising substance will vary with pH as the ionised species will have a greater hydrophilicity and lower log K_ow than the neutral species.

For further details of the speciation of BHMT-H see PFA 2020.

In a secondary source, a limit log K_ow value of <0 was reported for the substance, full details are not available and the reliability is unassignable.

HMDTMP-H is a named impurity in the registered substance. Log K_ow values of -4.7 and -4.1 at 100 ppm and 1000 ppm respectively were reported for HMDTMP-H in a reliable study conducted according to generally accepted scientific principles comparable to an appropriate test guideline. The method has been adequately described in the report.

Reference:

PFA 2020: BHMT speciation at pH relevant to Ecotoxicology and Toxicology, Reference: PFA.224.603.001, June 2020.