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Partition coefficient

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Endpoint:
partition coefficient
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Data are well documented and scientifically acceptable. Data are not gathered according to guidelines.
Reason / purpose:
reference to same study
Principles of method if other than guideline:
At least two different concentrations of DBPP (100 ppm - 1 %) were prepared in octanol. Octanol solutions and water were added into a glass bottle and shaken for 48 h. The mixture was then transferred to a separatory funnel and allowed to stand for 1 week in the dark. Then samples were taken from the aqueous phase, extracted and analyzed. The partition coeft was calculated according to: P = Co/Cw

There were no additional measurements carried out with the octanol phase as negligible amounts were found in the water phase.
GLP compliance:
no
Type of method:
shake-flask method to: flask method
Partition coefficient type:
octanol-water
Analytical method:
gas chromatography
Type:
Pow
Partition coefficient:
18 800
Temp.:
20 °C
pH:
7
Conclusions:
DBPP has a Pow of 18800 (log Pow = 4.27)
Executive summary:

The octanol/water partition coefficient of DBPP was measured by preparing octanol solutions of DBPP and shaking them with water. The mixture was then allowed to stand for 1 week in the dark. Subsequently samples were taken, extracted and analyzed. The partition coefficient was calculated according to: P = Co/Cw.

The octanol/water partition coefficient for DBPP, which was derived from these measurements equalled 18800 (or Log Pow = 4.27).

Endpoint:
partition coefficient
Type of information:
(Q)SAR
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
results derived from a (Q)SAR model, with limited documentation / justification, but validity of model and reliability of prediction considered adequate based on a generally acknowledged source
Justification for type of information:
QSAR prediction
Reason / purpose:
reference to same study
Qualifier:
according to
Guideline:
other: Meylan, W.M. and P.W. Howard. Atom/fragment contribution method for estimating octanol-water partition coefficients. J. Pharm. Sci. 84: 83 - 92, 1995
Deviations:
no
Principles of method if other than guideline:
The partition Coefficient is calculated with a QSAR based on a Fragment constant approach. IN this approach a molecule is divided in distinct atoms/fragments; For each fragment (depending on the neighbouring groups) a coefficient value is calculated, which are summed together to yield the log P estimate.
GLP compliance:
no
Type of method:
other:
Partition coefficient type:
octanol-water
Type:
log Pow
Partition coefficient:
4.41
Remarks on result:
other: The QSAR is valid for ambient temperatures and a neutral pH
Conclusions:
log Pow = 4.41
Executive summary:

The log Kow of BDPP was estimated to be 4.41.

Log Kow of BDPP was estimated using a well defined QSAR, based on an elaborate training database and validation database. DBPP lies well within the applicability domain of the QSAR, therefore the result of the QSAR is considered to be a realistic estimate of the log Kow.

Endpoint:
partition coefficient
Type of information:
(Q)SAR
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
results derived from a (Q)SAR model, with limited documentation / justification, but validity of model and reliability of prediction considered adequate based on a generally acknowledged source
Justification for type of information:
QSAR prediction
Reason / purpose:
reference to same study
Qualifier:
according to
Guideline:
other: Meylan, W.M. and P.W. Howard. Atom/fragment contribution method for estimating octanol-water partition coefficients. J. Pharm. Sci. 84: 83 - 92, 1995
Deviations:
no
Principles of method if other than guideline:
The partition Coefficient is calculated with a QSAR based on a Fragment constant approach. IN this approach a molecule is divided in distinct atoms/fragments; For each fragment (depending on the neighbouring groups) a coefficient value is calculated, which are summed together to yield the log P estimate.
GLP compliance:
no
Type of method:
other:
Partition coefficient type:
octanol-water
Type:
log Pow
Partition coefficient:
4.11
Remarks on result:
other: The QSAR is valid for ambient temperatures and a neutral pH
Conclusions:
log Pow = 4.11
Executive summary:

The log Kow of DBPP was estimated to be 4.11.

Log Kow of DBPP was estimated using a well defined QSAR, based on an elaborate training database and validation database. DBPP lies well within the applicability domain of the QSAR, therefore the result of the QSAR is considered to be a realistic estimate of the log Kow.

Endpoint:
partition coefficient
Type of information:
(Q)SAR
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
results derived from a (Q)SAR model, with limited documentation / justification, but validity of model and reliability of prediction considered adequate based on a generally acknowledged source
Justification for type of information:
QSAR prediction
Reason / purpose:
reference to same study
Qualifier:
according to
Guideline:
other: Meylan, W.M. and P.W. Howard. Atom/fragment contribution method for estimating octanol-water partition coefficients. J. Pharm. Sci. 84: 83 - 92, 1995
Deviations:
no
Principles of method if other than guideline:
The partition Coefficient is calculated with a QSAR based on a Fragment constant approach. IN this approach a molecule is divided in distinct atoms/fragments; For each fragment (depending on the neighbouring groups) a coefficient value is calculated, which are summed together to yield the log P estimate.
GLP compliance:
no
Type of method:
other:
Partition coefficient type:
octanol-water
Type:
log Pow
Partition coefficient:
3.82
Remarks on result:
other: The QSAR is valid for ambient temperatures and a neutral pH
Conclusions:
log Pow = 3.82
Executive summary:

The log Kow of TBP was estimated to be 3.82.

Log Kow of TBP was estimated using a well defined QSAR, based on an elaborate training database and validation database. TBP lies well within the applicability domain of the QSAR, therefore the result of the QSAR is considered to be a realistic estimate of the log Kow.

Description of key information

The octanol/water partition coefficient of DBPP was measured by preparing DBPP solutions in octanol, shaking them with water and subsequently allowing the mixture to stand for 1 week. Then samples were taken extracted and analyzed. The partition coeft was calculated according to: P = Co/Cw. The partition coefficient for DBPP equalled 18800 (of log Pow = 4.27) (Saeger et al., 1979). Additionally, 3 QSAR estimations for the 3 main constituents are available. These were in the same range as the measured log Kow value.

Key value for chemical safety assessment

Log Kow (Log Pow):
4.27
at the temperature of:
20 °C

Additional information

The reaction mass of DiButyl Phenyl Phosphate (DBPP) also contains ca. 10% Tri Butyl Phosphate (TBP) and ca 20% Butyl DiPhenyl Phosphate (BDPP) and 70% DiButyl Phenyl Phosphate (DBPP).

For all three compounds a QSAR was run to estimate the log Kow. The QSAR is well defined, based on elaborate training and validation datasets and all three compounds fall well within the applicability domain of the QSAR:

compound              log Kow

DBPP                     4.11

TBP                        3.82

BDPP                     4.41

For DBPP a measured log Kow value is also present; which equals 4.27. This is very close to the value calculated by the QSAR. However, since this is a measured value, this was the starting point for further calculations.

The QSAR values for the three compounds are considered to be reliable estimates of the actual values (which is confirmed by the measured value for DBPP) and do not give a reason to deviate from the measured log Kow value for DBPP.