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Adsorption / desorption

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Endpoint:
adsorption / desorption
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
Qualifier:
according to
Guideline:
other: The Molecular connectivity index approach was used, as was described by Meylan et al; Environmental Science and Technology, 26, 1560 - 1567, 1992
Principles of method if other than guideline:
The molecular connectivity (MCI) approach is used to derive the appropriate Koc value. For non-polar compounds the QSAR has a simple linear form: log Koc = 0.5213 MCI + 0.60. For more polar compounds corrections are made for the polar groups.
GLP compliance:
no
Type of method:
other: QSAR
Media:
other: QSAR
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
not applicable
Radiolabelling:
no
Test temperature:
The QSAR is applicable to ambient temperatures
Details on study design: HPLC method:
not applicable
Analytical monitoring:
not required
Details on sampling:
not applicable
Details on matrix:
not applicable
Details on test conditions:
not applicable
Type:
log Koc
Value:
3.5
Details on results (HPLC method):
not applicable
Adsorption and desorption constants:
not applicable
Recovery of test material:
not applicable
Concentration of test substance at end of adsorption equilibration period:
not applicable
Concentration of test substance at end of desorption equilibration period:
not applicable
Details on results (Batch equilibrium method):
not applicable
Statistics:
not applicable

The MCI model has a clear algorithm for this defined property of the compound. Currently there is no well defined model domain, however the modelling results will be less reliable if the molecular weight is not in the range of the molecular weights of the training and validation dataset. The molecular weight of BDPP falls well within the the molecular weight of the training and validation dataset.

The training dataset consists of 447 compounds of which some have similar structures to BDPP. The plot of experimental log Koc against modelled Koc has an R2 of 0.90, a SD of 0.34 and an average deviation of 0.273.

Validity criteria fulfilled:
yes
Conclusions:
With the MCI QSAR a log KOC of 3.50 was calculated.
Executive summary:

EPI Suite v4.10 was used to calculate the log Koc value of BDPP. The QSAR is based on the well documented MCI model and the resulting log Koc equals 3.50.

For this property of the compound, the model has a well defined algorithm. The physical and chemical properties of BDPP fall well within the the molecular weight of the training and validation dataset. The training dataset consists of 447 compounds of which some have similar structures to DBPP. The plot of experimental log Koc against modelled Koc has an R2 of 0.90, a SD of 0.34 and an average deviation of 0.273. Therefore the calculated value of log Koc can be considered to be reliable.

Endpoint:
adsorption / desorption
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
Qualifier:
according to
Guideline:
other: The Molecular connectivity index approach was used, as was described by Meylan et al; Environmental Science and Technology, 26, 1560 - 1567, 1992
Principles of method if other than guideline:
The molecular connectivity (MCI) approach is used to derive the appropriate Koc value. For non-polar compounds the QSAR has a simple linear form: log Koc = 0.5213 MCI + 0.60. For more polar compounds corrections are made for the polar groups.
GLP compliance:
no
Type of method:
other: QSAR
Media:
other: QSAR
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
not applicable
Radiolabelling:
no
Test temperature:
The QSAR is applicable to ambient temperatures
Details on study design: HPLC method:
not applicable
Analytical monitoring:
not required
Details on sampling:
not applicable
Details on matrix:
not applicable
Details on test conditions:
not applicable
Type:
log Koc
Value:
2.97
Details on results (HPLC method):
not applicable
Adsorption and desorption constants:
not applicable
Recovery of test material:
not applicable
Concentration of test substance at end of adsorption equilibration period:
not applicable
Concentration of test substance at end of desorption equilibration period:
not applicable
Details on results (Batch equilibrium method):
not applicable
Statistics:
not applicable

The MCI model has a clear algorithm for this property of the compound. Currently there is no well defined model domain, however the modelling results will be less reliable if the molecular weight is not in the range of the molecular weights of the training and validation dataset. The molecular weight of DBPP falls well within the the molecular weight of the training and validation dataset.

The training dataset consists of 447 compounds of which some have similar structures to DBPP. The plot of experimental log Koc against modelled Koc has an R2 of 0.90, a SD of 0.34 and an average deviation of 0.273.

Validity criteria fulfilled:
yes
Conclusions:
With the MCI QSAR a log KOC of 2.97 was calculated.
Executive summary:

EPI Suite v4.10 was used to calculate the log Koc value of DBPP. The QSAR is based on the well documented MCI model and the resulting log Koc equals 2.97.

For this well defined property of the compound, the model has a well defined algorithm. The physical and chemical properties of DBPP fall well within the the molecular weight of the training and validation dataset. The training dataset consists of 447 compounds of which some have similar structures to DBPP. The plot of experimental log Koc against modelled Koc has an R2 of 0.90, a SD of 0.34 and an average deviation of 0.273. Therefore the calculated value of log Koc can be considered to be reliable.

Endpoint:
adsorption / desorption
Remarks:
other: QSAR
Type of information:
(Q)SAR
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The study result is based on a QSAR, with a well documented model and the properties of the substance well within the applicability domain of the model.
Justification for type of information:
QSAR prediction
Qualifier:
according to
Guideline:
other: The Molecular connectivity index approach was used, as was described by Meylan et al; Environmental Science and Technology, 26, 1560 - 1567, 1992
Principles of method if other than guideline:
The molecular connectivity (MCI) approach is used to derive the appropriate Koc value. For non-polar compounds the QSAR has a simple linear form: log Koc = 0.5213 MCI + 0.60. For more polar compounds corrections are made for the polar groups.
GLP compliance:
no
Type of method:
other: QSAR
Media:
other: QSAR
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
not applicable
Radiolabelling:
no
Test temperature:
The QSAR is applicable to ambient temperatures
Details on study design: HPLC method:
not applicable
Analytical monitoring:
not required
Details on sampling:
not applicable
Details on matrix:
not applicable
Details on test conditions:
not applicable
Type:
log Koc
Value:
3.37
Details on results (HPLC method):
not applicable
Adsorption and desorption constants:
not applicable
Recovery of test material:
not applicable
Concentration of test substance at end of adsorption equilibration period:
not applicable
Concentration of test substance at end of desorption equilibration period:
not applicable
Details on results (Batch equilibrium method):
not applicable
Statistics:
not applicable

The MCI model has a clear algorithm for this defined property of the compound. Currently there is no well defined model domain, however the modelling results will be less reliable if the molecular weight is not in the range of the molecular weights of the training and validation dataset. The molecular weight of TBP falls well within the the molecular weight of the training and validation dataset.

The training dataset consists of 447 compounds of which some have similar structures to TBP. The plot of experimental log Koc against modelled Koc has an R2 of 0.90, a SD of 0.34 and an average deviation of 0.273.

Validity criteria fulfilled:
yes
Conclusions:
With the MCI QSAR a log KOC of 3.37 was calculated.
Executive summary:

EPI Suite v4.10 was used to calculate the log Koc value of TBP. The QSAR is based on the well documented MCI model and the resulting log Koc equals 3.37.

For this property of the compound, the model has a well defined algorithm. The physical and chemical properties of TBP fall well within the the molecular weight of the training and validation dataset. The training dataset consists of 447 compounds of which some have similar structures to DBPP. The plot of experimental log Koc against modelled Koc has an R2 of 0.90, a SD of 0.34 and an average deviation of 0.273. Therefore the calculated value of log Koc can be considered to be reliable.

Description of key information

Two independent well documented QSARs were used to calculate the log Koc for DBPP. The results of the QSARs are very similar with a value of 2.97 obtained with the MCI approach and a value of 3.06 with an approach based on the log Kow value.
As the MCI QSAR is considered slightly more reliable and the lowest value is considered more critical in the environmental assessment (aquatic compartment) this value as the key value for the CSA.

Key value for chemical safety assessment

Koc at 20 °C:
933

Additional information

Two independent QSARs were used to calculate the log Koc value of DiButyl Phenyl Phosphate (DBPP), Tri Butyl Phosphate (TBP) and Butyl DiPhenyl Phosphate (BDPP). The QSARs are well documented, have a clear regression model and are used for a well defined property for compounds that fall well within the applicability domain of the QSAR.

Compound       log Koc MCI-QSAR       log Koc Kow-QSAR

DBPP                     2.97                                   3.06

TBP                      3.37                                   3.24

BDPP                     3.50                                   3.14

The different compounds have similar Koc values and the different QSAR results are also similar. As the MCI-QSAR is considered to be slightly more reliable this is the starting point for further calculations. The Koc values of the two other compounds do not give reason to deviate from the value obtained for DBPP.

[LogKoc: 2.97]