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Partition coefficient

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Reference
Endpoint:
partition coefficient
Type of information:
experimental study
Adequacy of study:
key study
Study period:
09 November 2017 - 17 November 2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other:
Remarks:
This study was considered as reliable without restriction because it was conducted under GLP without deviation and with certificate of analysis included.
Reason / purpose:
reference to same study
Reason / purpose:
reference to other study
Qualifier:
according to
Guideline:
OECD Guideline 123 (Partition Coefficient (1-Octanol / Water), Slow-Stirring Method)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method A.23 Partition Coefficient (1-Octanol/Water): Slow-Stirring Method
Deviations:
no
GLP compliance:
yes (incl. certificate)
Remarks:
2017-01-10
Type of method:
slow-stirring method
Partition coefficient type:
octanol-water
Analytical method:
high-performance liquid chromatography
Key result
Type:
log Pow
Partition coefficient:
ca. 4.71
Temp.:
25 °C
Remarks on result:
other: +/- 0.5 °C

Experimental data:

The concentrations obtained in both phases and the corresponding log Pow are presented as a function of time during the three independent slow-stirring experiments in the following tables.

Vessel 1
Sampling date  Water phase concentration (mg/L) Octanol phase concentration (mg/L) log Pow
10/11/2017 08:30 0.128 4760.5 4.57
10/11/2017 14:00 0.114 4618.4 4.61
13/11/2017 08:00 0.078 3907.2 4.70
13/11/2017 14:00 0.072 3811.6 4.72
14/11/2017 08:00 0.060 3459.6 4.76
14/11/2017 14:30 0.057 3116.6 4.74

 15/11/2017 07:45

 0.053

 2523.8

 4.68

 15/11/2017 13:00

 0.055

 2197.1

 4.60

 16/11/2017 08:00

 0.045

 2433.6

 4.73

 16/11/2017 14:00

 0.040

 2328.9

 3.08

 17/11/2017 08:00

 0.041

 1951.8

 2.95

Vessel 2
Sampling date  Water phase concentration (mg/L) Octanol phase concentration (mg/L) log Pow
13/11/2017 14:00 0.078 4028.9 4.71
14/11/2017 08:00 0.069 3448.8 4.70
14/11/2017 14:30 0.061 2843.1 4.67
15/11/2017 07:45 0.037 2081.0 4.75
15/11/2017 13:00 0.033 1813.3 4.74
16/11/2017 08:00 0.026 1507.5 4.76
 16/11/2017 14:00  0.028  1387.2  4.70
 17/11/2017 08:00 0.027  1229.3  4.66

Vessel 3
Sampling date  Water phase concentration (mg/L) Octanol phase concentration (mg/L) log Pow
13/11/2017 14:00 0.088 4523.7 4.71
14/11/2017 08:00 0.065 3154.8

4.68

14/11/2017 14:30

0.075

3007.9

4.60

15/11/2017 07:45

0.046

2481.8

4.73

15/11/2017 13:00

0.036

2050.3

4.75

16/11/2017 08:00

0.047

2177.8

4.66

16/11/2017 14:00

 0.037  2032.8  4.74

 17/11/2017 08:00

 0.032  1780.0  4.75

Demonstration of the chemical equilibrium:

The log Pow was calculated for each sampling time and chemical equilibrium was demonstrating by plotting this ratio against time. A plateau in this plot indicated that equilibrium was attained and that the compound was truly dissolved in octanol. If not, the test needed to be continued until four successive time points yielded a slope that was significantly different from zero at a p-level of 0.05, indicating that log Pow was independent of time.

An hypothesis test for regression slope was carried out to demonstrate the equilibrium state of the system. The first step was to state the null hypothesis and an alternative hypothesis:

H0: The slope of the regression line was equal to zero.

Ha: The slope of the regression line was not equal to zero.

If the relationship between log Pow and time was significant, the slope would not be equal to zero. For this analysis, the significance level was 0.05. Using sample data, a linear regression t-test was conducted to determine whether the slope of the regression line differed significantly from zero. To apply the linear regression t-test to sample data, the slope of the regression line, the standard error of the slope, the degrees of freedom, the t-score test statistic, and the P-value of the statistical test were required.

Two degrees of freedom were chosen due to the four observations used.

According to the student distribution tables with two degrees of freedom and a significance level of 0.05, H0 could be accepted if:

-4.303 < t < 4.303

The sampling time period used for this equilibrium demonstration was from 13/11/2017 14:00 to 15/11/2017 07:45.

The results of this statistical test are presented in the following tables:

 
 Vessel 1  Vessel 2  Vessel 3
 Slope  -2.72E-02  1.44E.02  2.25E-03
 Standard error  3.03E-0.  2.94E.02  5.44E-02
 t value  -0.90  0.49  0.04
 Equilibrium ?  YES  YES  YES

Since all the t values were included in the [-4.303;4.303] interval, the equilibrium state can be declared for all the vessels and all the isomer groups between 13/11/2017 14:00 to 15/11/2017 07:45.

Log Pow calculation:

The following tables present the log Pow for each vessel and their corresponding statistical weights (wi)

 

 
   log Pow i  wi
 Vessel 1  4.72  753
 Vessel 2  4.71

 1000

 Vessel 3

 4.68

326

The average log Pow are:

log Pow,Av = 4.71 + 0.01

Calculation of the mass balance:

The mass balance in each system can be calculated knowing the measured concentration in both phases at the equilibrium state and the introducedamount of test item.

The mass balance between 13/11/2017 14:00 to 15/11/2017 07:45 for each vessel are presented below:

 
 Time  Vessel 1  Vessel 2  Vessel 3
 13/11/2017 14:00  78.4%  82.9%  93.0%
 14/11/2017 08:00  71.2%  70.9%  64.9%
 14/11/2017 14:30  64.1%  58.5%  61.9%
 15/11/2017 07:45  51.9%  42.8%  51.0%
 Average  66.4%  63.8%  67.7%

A progressive loss of test item was observed during the study. Nevertheless, the loss occurred at the same rate in both phases because the log Pow value was constant during the study. This test item loss did not seem to have an impact on its log Pow determination.

Conclusions:
The Partition Coefficient determined by the slow-stirring method at 25°C +/- 0.5°C for the (E,Z)-2,6-DIMETHYLOCTA-2,4,6-TRIENE was:
log Pow,AV = 4.71 ± 0.01
Executive summary:

A study was performed to assess the partition coefficient of test item (E,Z)-2,6-DIMETHYLOCTA-2,4,6-TRIENE by the slow stirring method.

Three determinations were carried out at 25 °C +/- 0.5°C. 50 mL of octanol saturated with water containing 5 g/L of the test item were equilibrated with 500 mL of ultra-pure water saturated by octanol. Equilibrium was obtained when the observed log Pow reached a plateau. The test item concentrations were monitored in both phases by HPLC/DAD.

Based on the weighted average of the three determinations with the slow-stirring method, the partition coefficient determined at 25 °C +/- 0.5 °C for the (E,Z)-2,6-DIMETHYLOCTA-2,4,6-TRIENE was:

log Pow,AV = 4.71 + 0.01

Description of key information

The partition coefficient of (E,Z)-2,6-DIMETHYLOCTA-2,4,6-TRIENE was determined at 25°C by slow-stirring method according to OECD guideline 123.

log Pow = 4.71 ± 0.01

Key value for chemical safety assessment

Log Kow (Log Pow):
4.71
at the temperature of:
25 °C

Additional information

Key study conducted according to OECD guideline 123. The result is scientifically acceptable and obtained under GLP.

Therefore a reliability of 1 (reliable without restrictions) was assigned.