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Partition coefficient

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Endpoint:
partition coefficient
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2012-11-05 to 2012-12-11
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
The study was conducted according to an internationally recognised method. All validity criteria are fulfilled. Purity and isomers composition are available from the notifier. Therefore full validation applies.
Reason / purpose:
reference to other study
Reason / purpose:
reference to other study
Qualifier:
according to
Guideline:
OECD Guideline 123 (Partition Coefficient (1-Octanol / Water), Slow-Stirring Method)
GLP compliance:
yes (incl. certificate)
Remarks:
UK GLP compliance monitoring programme (inspected on 18th-20th June 2012, signed 19/09/2012)
Type of method:
slow-stirring method
Partition coefficient type:
octanol-water
Specific details on test material used for the study:
- Storage condition of test material: Room temperature.
Analytical method:
gas chromatography
Type:
Pow
Partition coefficient:
29 000
Temp.:
25 °C
pH:
7.3
Key result
Type:
log Pow
Partition coefficient:
4.46
Temp.:
25 °C
pH:
7.3
Remarks on result:
other: sum of the three major components

Sampling time (hours) organic phase (mg/L) aqueous phase (mg/L) Kow log Kow pH of
aqueous phase
Vessel 1 18 4891 0.1637 29900 4.48 7.3
24 4949 0.1756 28200 4.45 7.3
42 4864 0.1717 28300 4.45 7.3
47 4979 0.1747 28500 4.45 7.3
Vessel 2 18 4926 0.1691 29100 4.46 7.3
24 4953 0.1794 27600 4.44 7.3
42 4945 0.1773 27900 4.45 7.3
47 4950 0.1760 28100 4.45 7.3
Vessel 3 18 4855 0.1606 30200 4.48 7.3
24 5134 0.1701 30200 4.48 7.3
42 4925 0.1692 29100 4.46 7.3
47 5375 0.1721 31200 4.49 7.3

Overall mean log Kow = 4.46

Equilibrium was achieved over the initial four sampling occasions – it was confirmed that plotting log10Pow against time yielded a slope not significantly different from 0 at a p-level of 0.05.

The detector calibration was found to be linear over the range 0 to 5 mg/l of standard solutions in hexane with a regression coefficient (r) of 0.9999.

Satisfactory recoveries of approximately 102 and 103% of test substance from fortified control samples in n-octanol and pure water were achieved, whilst no significant interfering peaks were evident in blank control solutions.

Based on the stock concentration of 5.0 g/L, the measured n-octanol phase concentrations confirmed that a satisfactory mass balance (> 98% in each test vessel) had been achieved (a negligible amount was measured in the aqueous phase). It was considered that the measured concentrations in n-octanol and water were below 70% of the solubility in the respective phases – the test substance dissolved readily in n-octanol at the selected test level, whilst aqueous phase concentrations were well below the known water solubility (11.6 mg/L; please refer to IUCLID section 4.8)

Conclusions:
The substance has potential to bioaccumulate in the environment, according to CLP classification criteria for aquatic chronic toxicity (log Kow >4).
Executive summary:

The partition coefficient of the test substance was measured according to the OECD 123 guideline, slow-stirring method.

Each phase was analysed by GC, as the sum of the three major peaks. Recovery, linearity of calibration and mass balance were checked, and no surface-activity is anticipated under testing conditions. The average value of the three replicates was retained.

The partition coefficient (log Kow) of the test substance has been determined to be 4.46 (at 25°C and pH 7.3).

Endpoint:
partition coefficient
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
1999-06-14 to 1999-08-07
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
The study was conducted according to an internationally recognised method. Purity and isomers composition are available from the notifier. However, surface active potential should be considered. Therefore validation applies with restrictions.
Reason / purpose:
reference to other study
Qualifier:
according to
Guideline:
EU Method A.8 (Partition Coefficient)
GLP compliance:
yes (incl. certificate)
Remarks:
UK GLP compliance programme (inspected on 23rd March 1998/ signed on 21st July 1998)
Type of method:
HPLC method
Partition coefficient type:
octanol-water
Specific details on test material used for the study:
Storage condition of test material: room temperature, in the dark, under nitrogen.
Analytical method:
high-performance liquid chromatography
Type:
Pow
Partition coefficient:
55 300 - 61 600
Temp.:
30 °C
pH:
5.4
Type:
log Pow
Partition coefficient:
4.74 - 4.79
Temp.:
30 °C
pH:
5.4
Remarks on result:
other: 2 peaks

Preliminary estimate

Approximate solubility in n-octanol: >6.21 x 104 mg/L

Approximate solubility in water: < 13.6 mg/L

Approximate Pow: > 4.6 x 103

log10 Pow: > 3.7

Definitive test

Calibration

The retention times of thiourea and the reference standards, the capacity factors (k) and log10Pow values for the reference standards are shown in the table below:

  Retention times (mins) Mean retention time (mins) Capacity factor (k) log10 k log10 Pow
Injection 1 Injection 2
Thiourea (dead time) 2.493 2.453 2.473  -
Benzene 5.827 5.826 5.827 1.356 0.132 2.1
Toluene 7.970 7.968 7.969 2.222 0.347 2.7
Naphthalene 9.784 9.784 9.784 2.956 0.471 3.6
Phenanthrene 18.679 18.631 18.655 6.543 0.816 4.5
Triphenylamine 43.801 43.878 43.840 16.727 1.223 5.7
DDT 62.513 62.676 62.595 24.311 1.386 6.2

Log10Pow = slope x Log10K + intercept

slope = 3.2446

intercept = 1.7675

determination coefficient (r2) = 0.9886

Partition coefficient of sample

The retention times, capacity factors (k) and log10Pow values for the sample are shown in the table below:

Peak Injection Retention times (mins) Capacity factor (k) log10 k log10 Pow
1 1 22.797 8.218 0.915 4.743
2 22.794 8.217 0.915 4.742
2 1 23.480 8.495 0.929 4.790
2 23.480 8.495 0.929 4.790
Executive summary:

The partition coefficient of the test substance was measured according to the EU A8 guideline, HPLC method.

The system was calibrated with 6 reference substances. The sample chromatographed with 2 peaks within the calibration range; values were interpolated from the linear regression.

The partition coefficient (log Kow) of the test substance isomers has been determined to range between 4.74 and 4.79 (at 30°C and pH 5.4).

Description of key information

Partition coefficient calculated as the sum of the three major isomers. No significant difference between isomers.

The substance has potential for bioaccumulation, according to CLP classification criteria for aquatic chronic toxicity (log Kow >4).

Key value for chemical safety assessment

Log Kow (Log Pow):
4.46
at the temperature of:
25 °C

Additional information

A fully reliable experimental study, conducted according to a recognized OECD method and under GLP, is available. Therefore, it is considered as a key study, and the result is retained as key value for purpose of CSA.

A supporting study, conducted with the HPLC method, shows no significant difference between isomers (0.05 unit).