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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:
2018-11-20 to 2019-02-07
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 107 (Partition Coefficient (n-octanol / water), Shake Flask Method)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method A.8 (Partition Coefficient - Shake Flask Method)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Type of method:
flask method
Partition coefficient type:
octanol-water
Analytical method:
high-performance liquid chromatography
Key result
Type:
log Pow
Partition coefficient:
-0.7
Temp.:
23 °C
pH:
>= 5.4 - <= 5.6
Details on results:
Preliminary Test
The preliminary test at room temperature showed, that the octanol solubility of the test item was in the range of 58 g/L and 179 g/L.

Preliminary Test

The preliminary test at room temperature showed, that the octanol solubility of the test item was in the range of 58g/L and 179|g/L.

 

Preliminary test for the octanol solubility

Total amount of
added test item [g]

Volume of octanol [mL]

Stirring time at
RT [min]

Remark

0.58

10

50

dissolved

1.79

10

165

not dissolved

 

With the water solubility of 3000 to 3500 g/L, and the solubility in octanol of 58to179g/L, estimated from this preliminary test, the partition coefficient can be estimated to be between -1.3 and -1.7. For the determination of the log Pow in this range the shake flask method is recommended.

 

Main Test

The phases of the shake-flask-method were measured twice by means of HPLC.

 

Concentrations in the aqueous phases

separating
funnel

pH values*1

measured concentration

(g/L)

mean concentration*2
(mg/L)

1a

5.5

69.5 /66.3

339

1b

5.4

77.4/75.2

381

2a

5.4

68.0 /68.3

341

2b

5.6

65.6/63.9

324

3a

5.5

108.8/113.2

555

3b

5.5

111.4/108.4

549

*1at a temperature of 23 °C

*2 under consideration of the dilution factor 5

 

Concentrations in the octanol phases

separating
funnel

measured concentration

mean concentration

1a

66 2 /64 5

65 4

1b

64 2 /63 0

63 6

2a

59 4 /61 0

60 2

2b

53 4 /604

59 4

3a

1 03 0 / 1 01 0

102 0

3b

101 9 /105 2

103 5

The total amount of test item found in the two phases, the recovery rate and the partition coefficients are shown As 20 mL of the stock solution were added to each separating funnel, each funnel should contain 15 64 mg of the test item.

 

Results of the shake-flask-method

separating
funnel

total amount of
test item in the
separating funnel
(mg)

recovery rate (%)

Pew

log Pow

1a

14 33

95 1

0 193

-0 7

1b

16 52

105 6

0 167

-0 3

2a

16 04

102 6

0 177

-0 3

2b

15 32

93 0

0 134

-0 7

3a

15 13

97 1

0 134

-0 7

3b

15 13

96 7

0 133

-0 7

mean value

-0.7

standard deviation

<0.1

 

The recovery rate of the measured standard solutions was in the range from 96.3 % to 100.8 %, which shows a good accuracy of the analytical method.

 

Conclusions:
The partition coefficient of the test item was determined at 23 °C (pH 5.4 –5.6) by means of the shake-flask-method to be log Pow = -0.7 ± <0.1.
Executive summary:

 A study was conducted in accordance with OECD TG 107 and Regulation (EC) No 440/2008 method A.8 to determine the partition coefficient of the test substance using the shake flask method. The equilibrium concentration of the test item in both phases was determined by means of UV/VIS. After adding the different amounts of stock solution, pre-saturated double distilled water and pre-saturated 1-octanol, the funnels were shaken for approx. 10 minutes in a shaking apparatus. After shaking the phases were allowed to separate in the funnels. Subsequently, 10 mL of each phase were centrifuged for 30 minutes at 20 °C and 15000 rpm. For the analytical measurement by means of UV/VIS spectroscopy the centrifuged clear water phases as well as the clear octanol phases were measured without prior dilution steps. The pH values of all water phases were measured. The phases of the shake-flask-method were measured twice. The partition coefficient of the test item was determined at 23 °C (pH 5.4 –5.6) by means of the shake-flask-method to be log Pow = -0.7 ± <0.1.

Description of key information

The partition coefficient of the test item was determined at 23 °C (pH 5.4 –5.6) by means of the shake-flask-method to be log Pow = -0.7 ± <0.1.

Key value for chemical safety assessment

Log Kow (Log Pow):
-0.7
at the temperature of:
23 °C

Additional information

A study was conducted in accordance with OECD TG 107 and Regulation (EC) No 440/2008 method A.8 to determine the partition coefficient of the test substance using the shake flask method. The equilibrium concentration of the test item in both phases was determined by means of UV/VIS. After adding the different amounts of stock solution, pre-saturated double distilled water and pre-saturated 1-octanol, the funnels were shaken for approx. 10 minutes in a shaking apparatus. After shaking the phases were allowed to separate in the funnels. Subsequently, 10 mL of each phase were centrifuged for 30 minutes at 20 °C and 15000 rpm. For the analytical measurement by means of UV/VIS spectroscopy the centrifuged clear water phases as well as the clear octanol phases were measured without prior dilution steps. The pH values of all water phases were measured. The phases of the shake-flask-method were measured twice. The partition coefficient of the test item was determined at 23 °C (pH 5.4 –5.6) by means of the shake-flask-method to be log Pow = -0.7 ± <0.1.