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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:
19 October 2006 to 23 November 2006
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)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Type of method:
shake-flask method to: flask method
Partition coefficient type:
octanol-water
Analytical method:
high-performance liquid chromatography
Type:
log Pow
Partition coefficient:
-6.4
Temp.:
20 °C
Remarks on result:
other: pH not specified in the report
Details on results:
The partition coefficient n-octanol/water of the test item at room temperature, performed according to the flask method (individual solubilities in water and n-octanol}, was determined to:
log Pow -6.4

Preliminary Visual Estimation of the n-Octanol Solubility: Amounts of the test item were stirred with different amounts of n-octanol at room temperature.

Table 1: Appearance of the test mixtures

Amount of the test item in mg

Total volume in ml

Stirring time in min

Appearance of mixture

Solubility in g/l

228.8

4

50

Undissolved

 

8

30

Undissolved

 

18

35

Undissolved

 

28

45

Undissolved

 

48

40

Undissolved

 

68

150

Undissolved

 

118

1050

Undissolved

 

25.4

13

45

Undissolved

 

33

30

Undissolved

 

73

65

Undissolved

 

123

110

Undissolved

 

173

50

Undissolved

< 0.15

273

95

Dissolved

> 0.09

According to this preliminary test the solubility of the test item in n-octanol is between 0.09 g/l and 0.15 g/l (without correction for the purity).

 

Calculation of the Partition coefficient log Powfrom the preliminary tests: The partition coefficient Powmay be estimated from the saturation concentrations in n-octanol and water by the following equation:

Pow= cSoctanol/ cSwater

S = saturation

 

With the data obtained from the experiments the partition coefficient was calculated as log Pow-2. Due to this fact the partition coefficient n-octanol/water of the test item at ambient temperature had to be estimated from the individual solubilities in water and octanol.

 

Calculation of the Partition Coefficient Powfrom the Individual Solubilities: The saturation concentration of the test item in water was determined by means of the flask method in project 20060734.01 to 396.7 g/l (without correction for the purity).

 

Table 2: Octanol solubility of the test item – experiments A to D

Experiment

A

B

C

D (blank)

Amount of test item (g)

0.83

0.81

0.81

--

Stirring time at 20°C (h)

24

24

24

24

Aliquot (ml)

1

1

1

1

End volume (ml)

1

1

1

1

Measured concentration (mg/l)

<0.16 / <0.16

<0.16 / <0.16

<0.16 / <0.16

<0.16 / <0.16

Mean concentration (mg/l)

<0.16 / <0.16

<0.16 / < 0.16

<0.16 / <0.16

< 0.16 / <0.16

Octanol solubility (mg/l)

<0.16

<0.16

<0.16

<0.16

Average experiments A to C (without correction for the purity): <0.16 mg/l

From the individual solubilities thelog Powcan be calculated to-6.39.

 

Table 3: Concentrations of standards for recheck:

Standard

Measured concentration (mg/l)

% Recovery (mean value)

Standard 9 ( c = 85.1 mg/l)

82.1 – 82.6

96.8

Standard 8 (c = 106.4 mg/l)

103.4 / 103.4

97.2

Recoveries of the recheck samples ranged from 96.8% to 97.2%, indicating a good accuracy of the analytical method.

Conclusions:
The partition coefficient n-octanol/water of the test item at room temperature, performed according to the flask method (individual solubilities in water and n-octanol}, was determined to:
log Pow -6.4
Executive summary:

The objective of this study was the determination of the partition coefficient n-octanol/water of the test item according to the consolidated version of Guideline 67/548/EEC Annex V (Council Directive 92/69/EEC), PartA:Methods for determination of physico-chemical properties.A.8.partition coefficient n-octanol/water and OECD test guidelines, OECD 107 ( 1995), partition coefficient n-octanol/water. The study was performed in accordance with the Principles of Good Laboratory Practice (GLP) and reported with a valid GLP certificate.

 

The saturation concentration of the test item in water was estimated with the preliminary test in project 20060734.01 to be between 510 g/l and 610 g/l (without correction of the purity).

 

Preliminary Estimation of the n-Octanol Solubility: Two amounts of the test item were stirred at room temperature with increasing volumes of n-octanol. Due to the fact that the estimated log Powwas below -2, the partition coefficient n-octanol/water of the test item at room temperature had to be determined by the flask method.

 

Individual Solubilities in water and n-octanol: The saturation concentration of the test item in water was determined by means of the flask method in project 20060734.01.

The saturation concentration of the test item in n-octanol was also determined by means of the flask method:

Three flasks were prepared with about 0.8 g of the test item and 50 ml n-octanol. The batches were stirred for 24 h at 20°Cin tightly closed flasks. Parts of the saturated octanol phases were centrifuged (30 minutes, 20°C,15000 rpm). Another experiment was performed according to this procedure but without test item ("blank"= H).

 

With the data obtained from the experiments the partition coefficient was calculated as logPow-2. Due to this fact the partition coefficient n-octanol/water of the test item at ambient temperature had to be estimated from the individual solubilities in water and octanol.

The saturation concentration of the test item in water was determined by means of the flask method in project 20060734.01 to 396.7 g/l (without correction for the purity). Average experiments A to C (without correction for the purity): <0.16 mg/L

From the individual solubilities the log Pow can be calculated to-6.39.

 

The partition coefficient n-octanol/water of the test item at room temperature, performed according to the flask method (individual solubilities in water and n-octanol), was determined to: log Pow -6.4

Description of key information

The partition coefficient n-octanol/water of the test item at room temperature, performed according to the flask method (individual solubilities in water and n-octanol), was determined to: log Kow -6.4

Key value for chemical safety assessment

Log Kow (Log Pow):
-6.4
at the temperature of:
20 °C

Additional information

The partition coefficient n-octanol/water of the test item was determined according to methods A.8.partition coefficient n-octanol/water and OECD test guidelines, OECD 107 ( 1995), partition coefficient n-octanol/water. The saturation concentration of the test item in water was estimated with the preliminary test in project 20060734.01 to be between 510 g/l and 610 g/l (without correction of the purity).

The saturation concentration of the test item in n-octanol and water was determined by means of the flask method. Three flasks were prepared with about 0.8 g of the test item and 50 ml n-octanol. The batches were stirred for 24 h at 20°C in tightly closed flasks. Parts of the saturated octanol phases were centrifuged (30 minutes, 20°C,15000 rpm).

A further three flasks were prepared with about 17 g of the test item and 25 ml distilled water. The batches were stirred for different times at 30°C(experiment G for 72 h, experiment F for 48 h, experiment E for 24 h) in tightly closed flasks. After equilibration for 24 h at 20°C aliquots of the saturated aqueous phase were taken and centrifuged (30 minutes, 20°C,15000 rpm). Aliquots of the clear viscous aqueous phases were filtered through 0.2 μm membrane filters and diluted approx. 0.1 to 1 00 with the eluent at the beginning of the HPLC-measurement.

The saturation concentration of the test item in water was determined to be 396.7 g/l (without correction for the purity).

The saturation concentration of the test item in n-octanol was determined to be: <0.16 mg/L

From the individual solubilities the log Kow can be calculated to <-6.39.

 

The partition coefficient n-octanol/water of the test item at room temperature, performed according to the flask method (individual solubilities in water and n-octanol), was determined to: log Kow -6.4