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Physical & Chemical properties

Partition coefficient

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Endpoint:
partition coefficient
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Qualifier:
according to guideline
Guideline:
other: General Test Method for Measuring the Solubility of Organic Pigments (so-called “ETAD-method”)
Principles of method if other than guideline:
As determination of the octanol-water partition coefficient with standard methods is technically not feasible for the substance, the ETAD-method is applied. This method has been developed to assess the persistence and bioaccumulation properties of pigments (see also Guidance on Information Requirements and Chemical Safety Assessment Chapter R.11: PBT/vPvB assessment (Version 3.0)).
As a part of this method the water and octanol solubility of a pigment - after a thorough washing process - are determined separately. Then the ratio of the two solubilities is used as the octanol-water partition coefficient.
GLP compliance:
no
Type of method:
estimation method (solubility ratio)
Partition coefficient type:
octanol-water
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: A31506
- Expiration date of the lot/batch: -
- Purity test date: -

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing: Yes
- Preliminary purification step (if any): stirring in various solvents and filtration
- Final dilution of a dissolved solid, stock liquid or gel: -
- Final preparation of a solid: dry vacuuming at 160°C for 8 hours
Analytical method:
other: UV/Vis
Key result
Type:
log Pow
Partition coefficient:
ca. 2.4
Remarks on result:
other: No temperature is specified, but ambient conditions can be assumed. No pH indicated.
Details on results:
- The maximum absorption peak wavelength of PR 254 is 513 nm in water and n-octanol.
- Solubility of the PR 254 in water:
Peak height in the water-saturated solution: 0.00002
The water solubility of the PR 254 : Cwater= 0.4 ppb (= 0.0004 mg/L solvent)
- Solubility of the PR 254 in n-octanol:
Peak height in the n-octanol-saturated solution: 0.0097
The n-octanol solubility of the PR 254 : Cn-octanol = 103 ppb (= 0.103 mg/L solvent)

- Log Kow = Log (Cn-octanol / Cwater)
Conclusions:
The log kow of the registered substance has been determined as 2.4.
Executive summary:

Determination of the octanol-water partition coefficient with standard methods is technically not feasible for substances with very low water and octanol solubility. Therefore, the substance's solubility was determined using the estimation method (solubility ratio). In particular, the so-called the 'ETAD-method', which is specifically suitable for pigments and that uses UV/VIS to determine concentrations in solutions, has been applied. It has been developed to assess the persistence and bioaccumulation properties of pigments (see also Guidance on Information Requirements and Chemical Safety Assessment Chapter R.11: PBT/vPvB assessment (Version 3.0)). As a part of this method the water and octanol solubility of a pigment - after a thorough washing process - are determined separately. Then the ratio of the two solubilities is used to estimate the the octanol-water partition coefficient.

Using this approach, the log kow of the substance has been determined as 2.4 by calculating the ratio of the solubilities in octanol (0.103 mg/L) and in water (0.0004 mg/L).

Endpoint:
partition coefficient
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Justification for type of information:
1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The read-across is performed between two forms of the same substance. The identities of the two forms are describe below.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
The source form is 3,6-bis(4-chlorophenyl)-2,5-dihydropyrrolo[3,4-c]pyrrol-1,4-dione (EC-no. 401-540-3), referred to here as PR254. PR254 is an organic mono-constituent substance with a typical purity of > 99.5% (w/w). It does not contain any impurity relevant for classification or labelling of the substance.
The target form is the nanoform of the source substance, referred to here as PR254 nanoform. As the source form, it has a typical purity of > 99.5% (w/w) and it does not contain any impurity relevant for classification or labelling of the substance. The PR254 nanoform is spheroidal with a pure polyhedral shape and is not surface-treated.

3. ANALOGUE APPROACH JUSTIFICATION
The two analogue forms have the same structure. Under ambient atmosphere, the specific surface energy of particles increases with decreasing particle size. Therefore, particle aggregate to reach an energy minimum. The driving forces are hydrogen bonds and van der Waals forces (π-π interaction). Substantial energy is required to disperse the PR254 nanoform aggregates to particles that fall under the nanoform definition.
PR254 was been tested extensively addressing information requirements of Annexes VII to IX without identifying any biological target. PR254 nanoform could potentially have biological targets due to the different particle size distribution, which would require processes capable of dispersing the aggregates, e.g. in aqueous milieu. However, both forms have been tested according to OECD Test Guideline 318, demonstrating that PR254 nanoform cannot be dispersed under the condition of the study, i.e. immediately after sonification re-forms aggregates. Also, PR254 aggregates to a large extent, but can be more easily dispersed than the nanoform. The experiments demonstrated that exposure in aqueous milieu will be primarily to aggregates, regardless of the PR254 form.
Therefore, it is concluded that both forms will behave identically in studies, in which they are applied under atmospheric conditions and/or in aqueous milieus, so that for the PR254 nano-form no specific biological targets need to be considered.

Physico-chemical properties
Most physico-chemical properties (PCP) are inherent properties of a substance, which are not affected by the substance form. In addition, many PCP are determined starting the experimental procedure under ambient conditions, at which both forms have a similar particle size distribution. Therefore, the octanol-water partition coefficient will also be similar and the read-across from the source to the target form is scientifically justified.


4. DATA MATRIX
The data matrix is included as Annex 1 in the assessment report ‘PR254 bulk nano analogue approach 210111’ attached here below under ‘Attached justification’.
Reason / purpose for cross-reference:
reference to same study
Qualifier:
according to guideline
Guideline:
other: General Test Method for Measuring the Solubility of Organic Pigments (so-called “ETAD-method”)
Principles of method if other than guideline:
As determination of the octanol-water partition coefficient with standard methods is technically not feasible for the substance, the ETAD-method is applied. This method has been developed to assess the persistence and bioaccumulation properties of pigments (see also Guidance on Information Requirements and Chemical Safety Assessment Chapter R.11: PBT/vPvB assessment (Version 3.0)).
As a part of this method the water and octanol solubility of a pigment - after a thorough washing process - are determined separately. Then the ratio of the two solubilities is used as the octanol-water partition coefficient.
GLP compliance:
no
Type of method:
estimation method (solubility ratio)
Partition coefficient type:
octanol-water
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: A31506
- Expiration date of the lot/batch: -
- Purity test date: -

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing: Yes
- Preliminary purification step (if any): stirring in various solvents and filtration
- Final dilution of a dissolved solid, stock liquid or gel: -
- Final preparation of a solid: dry vacuuming at 160°C for 8 hours
Analytical method:
other: UV/Vis
Key result
Type:
log Pow
Partition coefficient:
ca. 2.4
Remarks on result:
other: No temperature is specified, but ambient conditions can be assumed. No pH indicated.
Details on results:
- The maximum absorption peak wavelength of PR 254 is 513 nm in water and n-octanol.
- Solubility of the PR 254 in water:
Peak height in the water-saturated solution: 0.00002
The water solubility of the PR 254 : Cwater= 0.4 ppb (= 0.0004 mg/L solvent)
- Solubility of the PR 254 in n-octanol:
Peak height in the n-octanol-saturated solution: 0.0097
The n-octanol solubility of the PR 254 : Cn-octanol = 103 ppb (= 0.103 mg/L solvent)

- Log Kow = Log (Cn-octanol / Cwater)
Conclusions:
The log kow of the registered substance has been determined as 2.4.
Executive summary:

Determination of the octanol-water partition coefficient with standard methods is technically not feasible for substances with very low water and octanol solubility. Therefore, the substance's solubility was determined using the estimation method (solubility ratio). In particular, the so-called the 'ETAD-method', which is specifically suitable for pigments and that uses UV/VIS to determine concentrations in solutions, has been applied. It has been developed to assess the persistence and bioaccumulation properties of pigments (see also Guidance on Information Requirements and Chemical Safety Assessment Chapter R.11: PBT/vPvB assessment (Version 3.0)). As a part of this method the water and octanol solubility of a pigment - after a thorough washing process - are determined separately. Then the ratio of the two solubilities is used to estimate the the octanol-water partition coefficient.

Using this approach, the log kow of the substance has been determined as 2.4 by calculating the ratio of the solubilities in octanol (0.103 mg/L) and in water (0.0004 mg/L).

Endpoint:
partition coefficient
Type of information:
(Q)SAR
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
accepted calculation method
GLP compliance:
no
Type of method:
flask method
Partition coefficient type:
octanol-water
Type:
log Pow
Remarks on result:
other: could not reliably be determined
Conclusions:
The log Pow could not be determined experimentally, but was estimated using KOWWIN, version 1.67, as 2.20.
Executive summary:

The log Pow could not be determined experimentally, but was estimated using KOWWIN, version 1.67, as 2.20.

Description of key information

The log kow of the non-nanoform of the registered substance has been determined as 2.4. This result is read-across to the nanoform.

Key value for chemical safety assessment

Log Kow (Log Pow):
2.4
at the temperature of:
20 °C

Additional information

The solubility of the non-nanoform of the registered substance

was determined using the estimation method (solubility ratio). The log kow of the non-nanoform

of the substance has been determined by the ratio of the solubilities in octanol (0.103 mg/L) and in water (0.0004 mg/L) resulting in a value of 2.4.

This result is read-across to the nanoform.