(E,Z)-2,6-dimethylocta-2,4,6-triene

Partition coefficient

Link to relevant study record(s)

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 for cross-reference:

reference to same study

Reason / purpose for cross-reference:

reference to other study

Qualifier:

according to guideline

Guideline:

OECD Guideline 123 (Partition Coefficient (1-Octanol / Water), Slow-Stirring Method)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method A.23 Partition Coefficient (1-Octanol/Water): Slow-Stirring Method

Deviations:

no

GLP compliance:

yes (incl. QA statement)

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 (w_i)

 

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.