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Physical & Chemical properties

Partition coefficient

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Reference
Endpoint:
partition coefficient
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2013-07-25 to 2013-07-30
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
EU Method A.8 (Partition Coefficient)
Deviations:
no
Qualifier:
according to
Guideline:
OECD Guideline 117 (Partition Coefficient (n-octanol / water), HPLC Method)
Deviations:
no
GLP compliance:
no
Remarks:
The study was conducted under GLP equivalent conditions. The study was conducted under supervision of a quality assurance unit which had ensured e.g instrumentation validation, reagent/materials certification, analyst certification and providing SOPs.
Type of method:
HPLC method
Partition coefficient type:
octanol-water
Analytical method:
high-performance liquid chromatography
Key result
Type:
log Pow
Partition coefficient:
1.3
Temp.:
20 °C
pH:
7
Remarks on result:
other: 4-methylpentane-2,2-diyl dihydroperoxide
Key result
Type:
log Pow
Partition coefficient:
4.2
Temp.:
20 °C
pH:
7
Remarks on result:
other: dioxybis-4-methylpentane-2,2-diyl dihydroperoxide
Details on results:
The capacity factor k for each reference substance was calculated from the average measured retention time tR of the substance and the average retention time of thiourea (= t0 is the dead time, i.e. the average time a solvent molecule needed to pass the column). The partition coefficient octanol/water (Kow) was deduced from the capacity factor (k) using a calibration plot of Log Kow versus Log k of the selected reference substances. The average measured Log Kow value for the test item was calculated with the retention time from two injections using the calibration plot of Log k versus Log Kow of the selected reference substances. Two peaks for the test substance were detected. Based on the molecular structure the peak response at the lowest retention time was considered to be representative for the monomer 4-methylpentane-2,2-diyl dihydroperoxide and the peak response at the highest retention time was considered to be representative for dioxybis-4-methylpentane-2,2-diyl dihydroperoxide. Values of log Kow derived from the different measurements fell within a range of ± 0.1 log units. The correlation coefficient R2 for the relationship between log k and log Kow of the reference substances was calculated to be higher than 0.9. Thus, all validation criteria were fulfilled.

Substance

log Kow theor.

Average net

retention time

(min)

Average

log k

Thiourea

-

0

 

Aniline

0.9

0.46

-0.53

Methyl benzoate

2.1

1.55

0.00

Bromobenzene

3.0

3.69

0.38

Phenantrene

4.5

12.19

0.90

Fluoranthene

5.1

18.74

1.08

4,4'-DDT

6.5

32.12

1.32

4-methylpentane-2,2-diyl dihydroperoxide

-

0.76

-0.31

dioxybis-4-methylpentane-2,2-diyl dihydroperoxide

-

7.71

0.70

 

Conclusions:
The log Pow of the monomer 4-methylpentane-2,2-diyl dihydroperoxide was determined to be 1.3 at 20 °C and the logPow of the dimer dioxybis-4-methylpentane-2,2-diyl dihydroperoxide was determined to be 4.2 at 20 °C respectively.
Executive summary:

A study was conducted in accordance with OECD TG 117 and Regulation (EC) No 440/2008 method A.8 to determine the partition coefficient of the test substance using the HPLC method. A solution of the test substance was prepared in methanol. The capacity factor k for each reference substance was calculated from the average measured retention time tR of the substance and the average retention time of thiourea. The partition coefficient octanol/water (Kow) was deduced from the capacity factor (k) using a calibration plot of Log Kow versus Log k of the selected reference substances. The linear regression parameters of the relationship log Pow = f(log k) were also calculated from the data obtained with the calibration mixture and, therewith, log Pow of the test substance was determined from its measured capacity factor. The value found for the partition coefficients n-octanol/water for the monomer (4-methylpentane-2,2-diyl dihydroperoxide ) are: 1.3 and for the dimer (dioxybis-4-methylpentane-2,2-diyl dihydroperoxide) 4.2 respectively. The determination was performed at 20 °C. Values of log Kow derived from the different measurements fell within a range of ± 0.1 log units. The correlation coefficient R2 for the relationship between log k and log Kow of the reference substances was calculated to be higher than 0.9. Thus, all validation criteria were fulfilled.

Description of key information

The log Pow of the monomer 4-methylpentane-2,2-diyl dihydroperoxide was determined to be 1.3 at 20 °C and the logPow of the dimer dioxybis-4-methylpentane-2,2-diyl dihydroperoxide was determined to be 4.2 at 20 °C respectively.

 

Key value for chemical safety assessment

Log Kow (Log Pow):
4.2
at the temperature of:
20 °C

Additional information

A study was conducted in accordance with OECD TG 117 and Regulation (EC) No 440/2008 method A.8 to determine the partition coefficient of the test substance using the HPLC method. A solution of the test substance was prepared in methanol. The capacity factor k for each reference substance was calculated from the average measured retention time tR of the substance and the average retention time of thiourea. The partition coefficient octanol/water (Kow) was deduced from the capacity factor (k) using a calibration plot of Log Kow versus Log k of the selected reference substances. The linear regression parameters of the relationship log Pow = f(log k) were also calculated from the data obtained with the calibration mixture and, therewith, log Pow of the test substance was determined from its measured capacity factor. The value found for the partition coefficients n-octanol/water for the monomer (4-methylpentane-2,2-diyl dihydroperoxide ) are: 1.3 and for the dimer (dioxybis-4-methylpentane-2,2-diyl dihydroperoxide) 4.2 respectively. The determination was performed at 20 °C. Values of log Kow derived from the different measurements fell within a range of ± 0.1 log units. The correlation coefficient R2 for the relationship between log k and log Kow of the reference substances was calculated to be higher than 0.9. Thus, all validation criteria were fulfilled.

 

The logPow of the third constituent was determined in a study according to OECD TG 117. The logPow of 4-methylpentan-2-one was determined to be 1.9 at pH 6.7 and 20 °C (Please refer to the ECHA disseminated dossier for more details).

 

In conclusion the logPow of the dimer was regarded as worst case assumption and was therefore chosen as key value for chemical safety assessment.