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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:
2019-07-15 to 2019-07-22
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:
photometric method
Key result
Type:
log Pow
Partition coefficient:
-0.3
Temp.:
26 °C
pH:
>= 3.5 - <= 3.7
Details on results:
The partition coefficient of the test item was determined at 26 °C (pH 3.5 – 3.7) by means of the shake-flask-method, according to OECD Test Guideline 107 (1995) to be log Pow = -0.3 ± < 0.1

Preliminary Test

The preliminary test at room temperature showed, that the octanol solubility of the test item was below 0.5 g/L. The observations of the preliminary test are summarized below.

 

Preliminary test for the octanol solubility

Amount of test item [g]

Total volume of added octanol [mL]

Stirring time at RT [min]

Remark

0.34

5

80

not dissolved

35

30

not dissolved

0.05

20

110

not dissolved

50

85

not dissolved

100

1,000

not dissolved

 With the water solubility between 0.1 g/L and 1.0 g/L determined in the preliminary test and the solubility in octanol below 0.5 g/L, determined in this preliminary test, the partition coefficient can be estimated to be between -0.3 and 0.7. For the determination of the log Powin this range the shake flask method is recommended.

 

Main Test

The phases of the shake-flask-method wereanalysedtwice by UV/VIS spectroscopy. The values represented in the table are rounded values. The calculation was carried out with the original not rounded values.

 

Concentrations in the aqueous phases

separating funnel

pH values*1

measured concentration [mg/L]

mean concentration
[mg/L]

1a

3.5

69.90 / 69.55

69.72

1b

3.7

67.66 / 67.45

67.56

2a

3.7

57.64 / 57.47

57.56

2b

3.7

57.34 / 57.12

57.23

3a

3.5

74.06 / 73.85

73.95

3b

3.5

75.76 / 75.52

75.64

*1at temperatures of 25.7 – 26.6 °C

 

Concentrations in the octanol phases

separating funnel

measured concentration [mg/L]

mean concentration
[mg/L]

1a

38.20 / 37.61

37.91

1b

37.49 / 37.33

37.41

2a

30.34 / 30.09

30.22

2b

29.67 / 29.55

29.61

3a

46.06 / 45.61

45.83

3b

46.53 / 46.38

46.46

 

The total amount of test item found in the two phases, the recovery rate and the partition coefficients are shown below. As 20 mL of the stock solution were added to each separating funnel, each funnel should contain 4.0 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 (%)

Pow

log Pow

1a

3.55

88.5

0.544

-0.3

1b

3.45

86.0

0.554

-0.3

2a

3.51

87.6

0.525

-0.3

2b

3.47

86.6

0.517

-0.3

3a

3.31

82.6

0.620

-0.2

3b

3.37

84.1

0.614

-0.2

mean value

-0.3

standard deviation

<0.1

 

 To verify the accuracy of the analytical method four fresh prepared standard solutions (prepared with the test item) were measured in between the samples of the shake-flask-method.

 

Measurement of standard solutions

Standard solution

(nominal value [mg/L])

Measured value [mg/L]

Recovery rate [%]

Ü1

(61.84)

61.76

99.9

62.34

100.8

Ü2

(87.06)

86.96

99.9

86.95

99.9

Ü3

(31.24)

31.09

99.5

31.07

99.5

Ü4

(58.90)

58.75

99.7

58.68

99.6

The recovery rate of the measured standard solutions was in the range from 99.5 % to 100.8 %, which shows a sufficient accuracy of the analytical method.

 

Conclusions:
The partition coefficient of the test item was determined to be logPow = -0.3 at 26 °C and pH 3.5 - 3.7.
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 as determined at 26 °C (pH 3.5 – 3.7) to be logPow = -0.3. 

Description of key information

The partition coefficient of the test item was determined to be logPow = -0.3 at 26 °C and pH 3.5 - 3.7 (reference 4.7 -1).

Key value for chemical safety assessment

Log Kow (Log Pow):
-0.3
at the temperature of:
26 °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 as determined at 26 °C (pH 3.5 – 3.7) to be logPow = -0.3.