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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:
2012-10-30 to 2012-11-17
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
The study was conducted according to an internationally recognised method, and under GLP. No deviation was reported. The substance is considered to be adequately characterised with its purity. Therefore full validation applies.
Qualifier:
according to
Guideline:
OECD Guideline 123 (Partition Coefficient (1-Octanol / Water), Slow-Stirring Method)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Remarks:
Inspected on 10July 2012 / Signed on 30 November 2012
Type of method:
slow-stirring method
Partition coefficient type:
octanol-water
Analytical method:
gas chromatography
Type:
log Pow
Partition coefficient:
5.09
Temp.:
25 °C
pH:
>= 6.4 - <= 7.3
Details on results:
The linearity of the detector response with respect to concentration was assessed over the nominal concentration ranges of 10 to 100 mg/L and 0.2 to 10 mg /L (n = 8 and n = 6 respectively). These were satisfactory with both having a correlation coefficient of 1.000 being obtained.

Recovery of analysis of the sample procedure was assessed and proved adequate for the test.
At a nominal test item concentration of 0.5 mg/L, a mean percentage recovery of 120 % was obtained (range 117 to 123 %). Aqueous sample concentrations have been corrected for recovery of analysis.

The mean stock solution concentration on analysis was 2.00 x 10E4 mg/L.
The mass balance based on the average of the 12 samples results used for the overall result gave a value of 98.5 % of the stock solution as weighed in.

Between 91 and 192 hours, 8 samples were collected for each phase in vessel 1. Four samples were collected for each phase in vessels 2 and 3 between 162 and 192 hours.

Individual results are available in the experimental reports.

Equilibrium was evident from at least 91 hours stirring. Taking the last four sets of analytical data for each vessel, the slope of the correlation was tested statistically to ensure it did not differ significantly from zero. This was performed using the t test and a probability value of P = 0.05 (critical value = 4.30 for 2 degrees of freedom).

As equilibrium was confirmed, the mean log10partition coefficient value, the standard deviation and variance was calculated for each vessel, taking the last four sets of analytical data for each vessel. This then allowed the final weighted average and standard deviation to be calculated as the definitive result for the test. The results are shown in the following table:

 

Vessel 1

Vessel 2

Vessel 3

Mean Log10Pow

5.09

5.09

5.08

Standard Deviation

1.10 x 10-2

1.94 x 10-2

1.38 x 10-2

Variance

1.20 x 10-4

3.77 x 10 -4

1.90 x 10-4

 

Weighted average Log10Pow:                       5.09

Variance weighted standard deviation:       3.71 x 10-3

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 ST 10 C 08 was measured under GLP according OECD 123 guideline, slow-stirring method. Three vessels were prepared, and four samples were taken in each phase after equilibration at 25°C, between 162 and 192 hours. The overall average was calculated weighted for the variance.

Log Kow = 5.09

Endpoint:
partition coefficient
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
1. HYPOTHESIS FOR THE ANALOGUE APPROACH

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)

3. ANALOGUE APPROACH JUSTIFICATION

4. DATA MATRIX

See attached justification document, included in IUCLID Section 13.
Reason / purpose:
read-across source
Key result
Type:
log Pow
Partition coefficient:
5.09
Temp.:
25 °C
pH:
>= 6.4 - <= 7.3
Conclusions:
(from analogue) The substance has potential for bioaccumulation (log Kow > 4), and aquatic chronic effects.
Executive summary:

The partition coefficient of the analogue test substance was measured under GLP according OECD 123 guideline, slow-stirring method. Three vessels were prepared, and four samples were taken in each phase after equilibration at 25°C, between 162 and 192 hours. The overall average was calculated weighted for the variance.

The derived Log Kow for the target substance is 5.09.

Description of key information

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

Key value for chemical safety assessment

Log Kow (Log Pow):
5.09
at the temperature of:
25 °C

Additional information

Four reliable experimental studies, conducted according to recognized OECD/EC methods, are available:

- one study, conducted with the slow-stir method, on the racemic substance, while the present dossier is for the (-)isomer,

- three studies, conducted with the HPLC method, on the parent substance.

The slow-stir study is of high quality, and no significant difference is anticipated between isomers, while the determinations by HPLC are out of the applicability range.

Therefore, the read-across will be preferred (key study), and the result is retained as key value for purpose of CSA.