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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:
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:
ca. 0.1
Temp.:
24 °C
pH:
>= 3.9 - <= 4.4

Preliminary Test:

The preliminary test at room temperature showed, that the octanol solubility of the test item was in the range of 5.7 g/L and 17 g/L. The observations of the preliminary test are summarized in Table 3.

Table 3: Preliminary test for the octanol solubility

Amount of test item [g]

Total volume of added octanol [mL]

Stirring time at RT [min]

Remark

0.17

10

35

Not dissolved

30

45

dissolved

With the water solubility of 28.8 to 64.9 g/L, estimated in the preliminary test of study no. CSL-18-0300.04, and the solubility in octanol of 5.7 to 17 g/L, estimated from this preliminary test, the partition coefficient can be estimated to be between -0.2 and -1.1. 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. The results of these measurements are summarized in Table 4 and Table 5.

The values represented in the table are rounded values. The calculation was carried out with the original not rounded values.

Table 4: Concentrations in the aqueous phases

Separating funnel

pH values*1

Measured concentrations (g/L)

Mean concentrations*2 (mg/L)

1a

4.4

0.37/ 0.38

1.50

1b

4.2

0.38/ 0.38

1.53

2a

4.2

0.27/ 0.27

1.09

2b

4.2

0.27/ 0.27

1.09

3a

3.9

0.36/ 0.35

1.41

3b

3.9

0.37/ 0.36

1.47

*1 at temperatures of 24 °C

*2 under consideration of the dilution factor 4

Table 5: Concentrations in the octanol phases

Separating funnel

Measured concentrations (g/L)

Mean concentrations*1(g/L)

1a

0.96/ 0.96

1.92

1b

1.19/ 1.18

2.38

2a

0.76/ 0.75

1.51

2b

0.76/ 0.78

1.54

3a

0.97/ 0.94

1.91

3b

0.97/ 0.97

1.94

*1under consideration of the dilution factor 2

In Table 6 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 96.74 mg of the test item.

Table 6: Results of the shake-flask-method 

Separating funnel

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

Recovery rate (%)

Pow

Log Pow

1a

98.3

102

1.280

0.1

1b

108.7

112

1.553

0.2

2a

103.8

107

1.391

0.1

2b

105.4

109

1.414

0.2

3a

104.6

108

1.354

0.1

3b

107.0

111

1.318

0.1

Mean value

0.1

Standard deviation

<0.1

The recovery rate in the flasks was slightly too high, but due to very consistent Pow values of all six flasks, and a good recovery rate of the measured standards (Table 7), the test was valid.

To verify the accuracy of the analytical method two freshly prepared standard solutions (prepared with the test item) were measured in between the samples of the shake-flask-method. The results of these measurements are shown in Table 7.

Table 7: Measurement of standard solution

Standard solution (nominal value [g/L])

Measured value [g/L]

Recovery rate [%]

Ü1 (0.2220)

0.224

101.9

0.216

98.5

Ü2 (0.445)

0.444

99.6

0.440

98.8

Ü3 (0.913)

0.913

100.0

0.926

101.4

Ü4 (1.365)

1.334

97.7

1.421

104.1

The recovery rate of the measured standard solutions was in the range from 97.7% to 104.1%, which shows a good accuracy of the analytical method.

Conclusions:
The log Pow of the test item Basic Red 1 was determined to be 0.1 ± < 0.1 at 24 °C (pH 3.9 - 4.4).
Executive summary:

The partition coefficient of the test item was determined by to the shake-flask-method according to the OECD Test Guideline 107 (1995) and EU Method A.8. The log Pow of the test item Basic Red 1 was determined to be 0.1 ± < 0.1 at 24 °C (pH 3.9 - 4.4).

Description of key information

The log Pow of the test item Basic Red 1 was determined to be 0.1 ± < 0.1 at 24 °C (pH 3.9 - 4.4).

Key value for chemical safety assessment

Log Kow (Log Pow):
0.1
at the temperature of:
24 °C

Additional information

The partition coefficient of the test item was determined by to the shake-flask-method according to the OECD Test Guideline 107 (1995) and EU Method A.8. The log Pow of the test item Basic Red 1 was determined to be 0.1 ± < 0.1 at 24 °C (pH 3.9 - 4.4).