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Partition coefficient

Link to relevant study record(s)

Reference

Endpoint:

partition coefficient

Type of information:

experimental study

Adequacy of study:

key study

Study period:

10-05-2021 to 21-06-2021

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline study performed under GLP. All relevant validity criteria were met.

Qualifier:

according to guideline

Guideline:

OECD Guideline 117 (Partition Coefficient (n-octanol / water), HPLC Method)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method A.8 (Partition Coefficient)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Other quality assurance:

other: inspected on August 18-20, 2021/ signed on March,17, 2021

Type of method:

HPLC method

Partition coefficient type:

octanol-water

Specific details on test material used for the study:

Storage conditions: Before first opening AND for short term storage of maximum 2 months: Dry area, protected from light and at room temperature / After first opening AND/OR for long term storage (more than 2 months): dry area, protected from light, in a refrigerator (temp 2-8°C) and store under Nitrogen in a closed container.

Analytical method:

high-performance liquid chromatography

Key result

Type:

log Pow

Partition coefficient:

ca. 3.53 - ca. 3.67

Temp.:

30 °C

pH:

ca. 5

Details on results:

The partition coefficient were determined for the two main constituents of the test item.

Preliminary test : The following table presents the retention times and the dead times (estimated with the peak of formamide) observed during this test for the reference items, the calculated k and log k and the log P_OW values found in the literature.

Compound	Concentration (mg/L)	tR (min)	t0 (min)	k	log k	log POW
Anisole	20	5.28	2.92	0.81	-0.09	2.1
Ethylbenzoate	11	6.04	2.90	1.08	0.03	2.6
Toluene	20	6.86	2.90	1.37	0.14	2.7
Ethylbenzene	30	8.53	2.90	1.94	0.29	3.2
Cumene	50	10.45	2.90	2.60	0.41	3.7
Biphenyl	10	11.53	2.90	2.98	0.47	4.0

 

The following equation was obtained:

log k = 0.3027 log P_OW - 0.7150                 with R = 0.9889 and R² = 0.9780.

For the test item, two peaks were observed with retention times of 9.33 min and 9.95 min. The dead time t₀, determined with the peak of formamide, was 2.91 min.

The log P_OW values corresponding to the peaks of the test item were then deduced from the previous equation:

Peak 1: log P_OW = 3.49 ; Peak 2: log P_OW = 3.62.

The coefficient of determination obtained with the reference solutions was higher than 0.95 and the retention times of the test item were included in the range of the retention times of the reference items. Therefore, these reference items were used for the main test.

 

MAIN TEST

Reference items :: The retention times of the reference items are presented in the table below:

Compound	tR 1 (min)	tR 2 (min)	ΔtR (min)	tR mean (min)	Δ tR / tR mean	Equilibrium? (<2%)
anisole	5.30	5.27	0.03	5.29	0.57%	YES
ethylbenzoate	5.99	6.01	0.02	6.00	0.33%	YES
toluene	6.84	6.83	0.01	6.84	0.15%	YES
ethylbenzene	8.55	8.53	0.02	8.54	0.23%	YES
cumene	10.43	10.45	0.02	10.44	0.19%	YES
biphenyl	11.58	11.63	0.05	11.61	0.43%	YES

with        t_R: retention time;

Δt_R: absolute value of the retention times difference.

The formamide, used for the determination of the dead time, had a retention time of 2.87 minutes in the first injection of the reference items mix and of 2.88 minutes in the second injection.

 

Log POW over log k : The following table presents, for each reference item, their log P_OW, the calculated retention factor for the two injections (k₁ and k₂), the mean of k₁ and k₂ (k mean), and log (k mean):

Compound	log Pow	k1	k2	k mean	log (k mean)
anisole	2.1	0.85	0.83	0.84	-0.08
ethylbenzoate	2.6	1.09	1.09	1.09	0.04
toluene	2.7	1.38	1.37	1.38	0.14
ethylbenzene	3.2	1.98	1.96	1.97	0.29
cumene	3.7	2.63	2.63	2.63	0.42
biphenyl	4.0	3.03	3.04	3.04	0.48

The logarithms of the mean capacity factors, log k, are plotted as a function of the logarithms of the partition coefficient, log P_OW.

The determination coefficient R² observed is 0.9835 and the correlation coefficient R is 0.9917. The equation of the line issued from this linear regression will be used for the test item log P_OW calculation.

 

 

Test item

-        Retention times and capacity factors

A typical chromatogram of the test item is constituted of two peaks. The retention times obtained are presented in the table below:

	Injection 1 tR (min)	Injection 2 tR (min)	Injection 3 tR (min)	Mean (min)	Relative standard deviation
Dead time t0	2.88	2.88	2.88	2.88	0.0%
Test item, peak 1	9.53	9.44	9.54	9.50	0.6%
Test item, peak 2	10.19	10.09	10.24	10.17	0.8%

 

-        Calculation of k, log k, and log P_OW

The calculated values for the test item peaks are presented in the following table. log P_OW is calculated using the regression equation obtained from the reference items:

log P_OW = (log k + 0.7107) / 0.3035

	Measurement No.	k	log k	log Pow
Peak 1	1	2.31	0,36	3,53
	2	2.28	0,36	3,53
	3	2.31	0,36	3,53
	log POW mean			3.53
	Standard Deviation			0.00
Peak 2	1	2.54	0,40	3,66
	2	2.50	0,40	3,66
	3	2.56	0,41	3,69
	log POW mean			3.67
	Standard Deviation			0.02

 

Results : Peak 1: log P_OW = 3.53; Peak 2: log P_OW = 3.67.

Conclusions:

Using the HPLC method, the following partition coefficients were determined for the two main constituents of the test item at 30°C and pH 5:
- Peak 1: log POW = 3.53;
- Peak 2: log POW = 3.67.
These values are the mean of three independent measurements.

Executive summary:

The partition coefficient of the test substance was measured under GLP according to the OECD 117/EU A8 guideline, HPLC method.

The system was calibrated with 6 reference substances, between logKow 2.1 and 4, and partition coefficient of the test substance was interpolated from the linear regression.

The partition coefficient (log Kow) of the test substance has been determined to be (at 30°C and pH 5.5) for the two main constituents of the test item:

Peak 1: log POW = 3.53; Peak 2: log POW = 3.67.

Description of key information

Log Pow= 3.53-3.67, at 30 ± 1 °C and ca. pH 5.0, HPLC method, OECD TG 117, 2021

Key value for chemical safety assessment

Log Kow (Log Pow):

3.67

at the temperature of:

30 °C

Additional information

Key study : OECD TG 117, 2021

A study was performed to assess the partition coefficient of the test item by the HPLC method. The method followed was designed to be compliant with the OECD Guideline for Testing of Chemicals No. 117, “Partition Coefficient (n-octanol/water): HPLC Method.

Six reference items with different retention times were used to produce the calibration curve. They were chosen in relation with the expected retention time of the test item. For each reference item, two determinations were performed. The capacity factor k was calculated from the retention time of formamide (dead time) and the retention time of the respective reference item. A calibration function (log k versus log POW, linear fit) was determined based on literature values of log POW for the reference items.

The following partition coefficient were determined for the two main constituents of the test item:

Peak 1: log POW = 3.53;  Peak 2: log POW = 3.67.

These values are the mean of from three independent measurements.