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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:
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 POW 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 POW - 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 POW values corresponding to the peaks of the test item were then deduced from the previous equation:


Peak 1: log POW = 3.49 ; Peak 2: log POW = 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        tR: retention time;


ΔtR: 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 POW, 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 POW.


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 POW 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 POW


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


log POW = (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 POW = 3.53; Peak 2: log POW = 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.