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Partition coefficient

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Reference
Endpoint:
partition coefficient
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 107 (Partition Coefficient (n-octanol / water), Shake Flask Method)
Version / remarks:
1995
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Type of method:
flask method
Partition coefficient type:
octanol-water
Analytical method:
high-performance liquid chromatography
Key result
Type:
log Pow
Partition coefficient:
< -3
Temp.:
20 °C
pH:
4.7
Key result
Type:
log Pow
Partition coefficient:
< -3
Temp.:
20 °C
pH:
6.8
Key result
Type:
log Pow
Partition coefficient:
< -3
Temp.:
20 °C
pH:
9

Table 1: Analysed concentrations, aqueous phase pH and resulting test item weights – pH 5

Sample number

Total weight (mg)

Organic phase

Aqueous phase

Mass recovery (%)

Analysed concentration (mg/L)

Weight (mg)

Analysed concentration (mg/L)

Weight (mg)

pH

1

27.6

<1.0

<0.054

996

26.9

4.7

97.5

2

27.6

<1.0

<0.054

1010

27.3

4.7

99.1

3

40.9

<1.0

<0.04

1020

40.7

4.7

99.5

4

40.9

<1.0

<0.04

1010

40.6

4.7

99.2

5

55.2

<1.0

<0.027

1020

55.0

4.7

99.7

6

55.2

<1.0

<0.027

1020

55.2

4.7

100.0

 

Table 2: Analysed concentrations, aqueous phase pH and resulting test item weights – pH 7

Sample number

Total weight (mg)

Organic phase

Aqueous phase

Mass recovery (%)

Analysed concentration (mg/L)

Weight (mg)

Analysed concentration (mg/L)

Weight (mg)

pH

1

26.7

<1.0

<0.054

996

26.9

6.8

100.7

2

26.7

<1.0

<0.054

995

26.9

6.8

100.6

3

39.6

<1.0

<0.04

1000

40.1

6.8

101.3

4

39.6

<1.0

<0.04

994

39.8

6.8

100.4

5

53.5

<1.0

<0.027

993

53.6

6.8

100.3

6

53.5

<1.0

<0.027

991

53.5

6.8

100.1

 

Table 3: Analysed concentrations, aqueous phase pH and resulting test item weights – pH 9

Sample number

Total weight (mg)

Organic phase

Aqueous phase

Mass recovery (%)

Analysed concentration (mg/L)

Weight (mg)

Analysed concentration (mg/L)

Weight (mg)

pH

1

26.8

<1.0

<0.054

997

26.9

9.0

100.7

2

26.8

<1.0

<0.054

1000

27.0

9.0

101.0

3

39.7

<1.0

<0.04

999

40.0

9.0

100.7

4

39.7

<1.0

<0.04

994

39.8

9.0

100.3

5

53.6

<1.0

<0.027

995

53.7

9.0

100.2

6

53.6

<1.0

<0.027

1000

54.0

9.0

100.7

 

Conclusions:
A log Kow <-3.0 was determined for the test substance under relevant environmental pH conditions (pH value ranging from 5 to 9) at a test temperature of 20 °C using the shake flask method.
Executive summary:

The octanol-water partition coefficient of the substance was determined under GLP in accordance with OECD TG 107, by using the shake flask method. For the determinations at specified pH conditions, individual buffer solutions were prepared and mutually saturated with n-octanol. Stock solutions of the test substance in the buffers were produced by diluting aliquots of 0.2549 g (pH 5), 0.2507 g (pH 7) and 0.2510 g (pH 9) in 250 mL of n-octanol saturated buffer solution. These were used as the aqueous phase in the test. The organic phase for the specific pH determinations was the relevant buffer solution saturated n-octanol. For each test conditions, six partitions were tested according to the following setup at a test temperature varying from 20 to 20.4 °C.

In each test, the combined volume of both phases occupied not less than 90% of the total volume of the test vessel. The organic and aqueous phases were equilibrated to the test temperature for a minimum of one hour before partitioning, which was performed by inversion of the flasks through approximately 180 °C over a five minute period. The test temperature was measured and confirmed at the time of partitioning and the flasks then returned to the 20 °C conditions to allow initial phase separation prior to decanting the individual phases for centrifugation. Individual aliquots of each phase from each vessel were taken and phase separation ensured by centrifugation at at leas 13000 rpm for 15 minutes. Aliquots of both phases from each vessel and each stock solution were taken for analysis by HPLC. The analysis of the organic phase sample solutions showed that the concentration of test substance was below the limit of quantification of the applied method (0.5 mg/L). A limit value of <1.0 mg/L in the organic phase was used in the calculation of Kow values (corrected for the dilution factor of 2). The Kow value at all tested pH values was <0.001. The resulting log Kow was thus <-3.0 at pH 5, 7 and 9 at a temperature of 20 °C.

Description of key information

log Kow <-3.0 at pH 5, 7, 9 and 20 °C (GLP, OECD TG 107, shake flask method)

Key value for chemical safety assessment

Additional information