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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:
2007-08-31 to 2007-09-19
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
GLP compliance:
yes (incl. QA statement)
Remarks:
Food and Consumer Product Safety Authority (WMA), Den Haag, The Netherlands / National GLP Compliance Monitoring Authority, New Delhi, India
Type of method:
flask method
Partition coefficient type:
octanol-water
Analytical method:
high-performance liquid chromatography
Key result
Type:
log Pow
Partition coefficient:
-1.12
Temp.:
20 °C
Remarks on result:
other: pH not reported
Remarks:
n-Octanol / Milli-Q water partition coefficient
Key result
Type:
log Pow
Partition coefficient:
-1.01
Temp.:
20 °C
Remarks on result:
other: pH not reported
Remarks:
n-Octanol / aqueous buffer pH4 partition coefficient
Key result
Type:
log Pow
Partition coefficient:
-2.48
Temp.:
20 °C
Remarks on result:
other: pH not reported
Remarks:
n-Octanol / aqueous buffer pH7 partition coefficient
Details on results:
The n-Octanol / aqueous buffer pH9 partition coefficient could not be calculated because the test item was not detected in the n-octanol phase of octanol / buffer pH 9.0 at 20 ± 1 °C due to its high water solubility at alkaline pH.

The concentration of the test item stock solutions prepared in n-octanol presaturated for the tests with Milli-Q water and pH 4.0, 7.0, and 9.0 aqueous buffer solutions were 72.28, 70.66, 70.29, and 70.56 µg/mL, respectively.

The mean partition coefficient (log Pow) of the test item was:

-1.07 ± 0.00, -1.17 ± 0.01, and -1.12 ± 0.01 for the octanol-Milli-Q water ratio of 1:1, 1:2, and 2:1 respectively at 20 ± 1 °C.

-1.01 ± 0.01, -1.02 ± 0.01, and -1.01 ± 0.00 for the octanol-pH 4.0 aqueous buffer solution ratio of 1:1, 1:2, and 2:1 respectively at 20 ± 1 °C.

-2.48 ± 0.01 and -2.48 ± 0.03 for the octanol-pH 7.0 aqueous buffer solution ratio of 1:1 and 2:1 respectively at 20 ± 1 °C while the test item was not detected in octanol phase of 1:2 ratio.

The test item was not detected in n-octanol phase of 1:1, 1:2, and 2:1 ratios of octanol-pH 9.0 aqueous buffer solution at 20 ± 1 °C.

 

The overall mean partition coefficient (log Pow) of the test item at 20 ± 1 °C were -1.12 ± 0.04, -1.01 ± 0.01, and -2.48 ± 0.02 for the n-octonal-Milli-Q water and n-octonal-aqueous buffers of pH 4.0 and 7.0, respectively. The test item was not detected in the n-octanol phase of 1:1, 1:2, and 2:1 ratios of octanol-buffer pH 9.0 at 20 ± 1 °C due to its high water solubility at alkaline pH.

 

The detailed results of the log Pow determination are given in the following tables.

 

Test results: partition coefficient n-Octanol / Milli-Q water

n-Octanol
to Milli-Q
water ratio

Replication
(R)

Volume of (mL)

Test item concentration
(µg/mL)

Amount (µg) of test item

Log Pow

Mean ±
S.D

n-Octanol

Milli-Q water

n-Octanol

Milli-Q water

n-Octanol

Milli-Q water

Total

Mean ± S.D

1:1

R1

50

50

5.50

64.97

275

3249

3524

3528 ± 5.66

-1.07

-1.07 ± 0.00

1:1

R2

50

50

5.50

65.13

275

3257

3532

-1.07

1:2

R1

50

100

2.29

34.25

115

3425

3540

3543 ± 4.24

-1.17

-1.17 ± 0.01

1:2

R2

50

100

2.37

34.27

119

3427

3546

-1.16

2:1

R1

100

50

4.71

61.72

471

3086

3557

3537 ± 28.99

-1.12

-1.12 ± 0.01

2:1

R2

100

50

4.71

60.89

471

3045

3516

-1.11

 

Overall log Pow mean ± S.D.: -1.12 ± 0.04

 

 

Test results: partition coefficient n-Octanol / pH 4.0 aqueous buffer solution

n-Octanol
to Buffer ratio

Replication
(R)

Volume of (mL)

Test item concentration
(µg/mL)

Amount (µg) of test item

Log Pow

Mean ±
S.D

n-Octanol

Buffer

n-Octanol

Buffer

n-Octanol

Buffer

Total

Mean ± S.D

1:1

R1

50

50

6.30

63.05

315

3153

3468

3482 ± 19.80

-1.00

-1.01 ± 0.01

1:1

R2

50

50

6.14

63.77

307

3189

3496

-1.02

1:2

R1

50

100

3.28

33.20

164

3320

3484

3526 ± 58.69

-1.01

-1.02 ± 0.01

1:2

R2

50

100

3.25

34.04

163

3404

3567

-1.02

2:1

R1

100

50

5.77

59.48

577

2974

3551

3528 ± 33.23

-1.01

-1.01 ± 0.00

2:1

R2

100

50

5.74

58.59

574

2930

3504

-1.01

 

Overall log Pow mean ± S.D.: -1.01 ± 0.01

 

 

Test results: partition coefficient n-Octanol / pH 7.0 aqueous buffer solution

n-Octanol
to Buffer ratio

Replication
(R)

Volume of (mL)

Test item concentration
(µg/mL)

Amount (µg) of test item

Log Pow

Mean ±
S.D

n-Octanol

Buffer

n-Octanol

Buffer

n-Octanol

Buffer

Total

Mean ± S.D

1:1

R1

50

50

0.23

70.62

12

3531

3543

3534 ± 12.73

-2.49

-2.48 ± 0.01

1:1

R2

50

50

0.24

70.26

12

3513

3525

-2.47

1:2

R1

50

100

-

34.59

-

3459

3459

3468 ± 12.02

-

-

1:2

R2

50

100

-

34.76

-

3476

3476

-

2:1

R1

100

50

0.22

69.46

22

3473

3495

3491 ± 5.66

-2.50

-2.48 ± 0.03

2:1

R2

100

50

0.24

69.26

24

3463

3487

-2.46

 

Overall log Pow mean ± S.D.: -2.48 ± 0.02

 

 

Test results: partition coefficient n-Octanol / pH 9.0 aqueous buffer solution

n-Octanol
to Buffer ratio

Replication
(R)

Volume of (mL)

Test item concentration
(µg/mL)

Amount (µg) of test item

Log Pow

Mean ±
S.D

n-Octanol

Buffer

n-Octanol

Buffer

n-Octanol

Buffer

Total

Mean ± S.D

1:1

R1

50

50

-

68.24

-

3412

3412

3415 ± 4.24

-

-

1:1

R2

50

50

-

68.36

-

3418

3418

-

1:2

R1

50

100

-

33.05

-

3305

3305

3314 ± 12.02

-

-

1:2

R2

50

100

-

33.22

-

3322

3322

-

2:1

R1

100

50

-

67.55

-

3378

3378

3376 ± 3.54

-

-

2:1

R2

100

50

-

67.45

-

3373

3373

-

 

The test item was not detected in n-octanol phase of 1:1, 1:2 and 2:2 ratios hence, log Pow values were not calculated.

Conclusions:
The octanol / water partition coefficient at 20 °C of the substance was determined using Milli-Q water and three aqueous buffer solutions (OECD Guideline 107, flask method):
-1.12 (octanol / Milli-Q water; pH of the solution not measured)
-1.01 (octanol / aqueous buffer pH4; pH of the solution not measured)
-2.48 (octanol / aqueous buffer pH7; pH of the solution not measured)
The n-Octanol / aqueous buffer pH9 partition coefficient could not be calculated because the test item was not detected in the n-octanol phase of octanol / buffer pH 9.0 at 20 ± 1 °C due to its high water solubility at alkaline pH.

Description of key information

log Pow = -1.12 at 20 °C in Milli-Q water

log Pow = -1.01 at 20 °C in pH 4.0 aqueous buffer solution

log Pow = -2.48 at 20 °C in pH 7.0 aqueous buffer solution

Key value for chemical safety assessment

Log Kow (Log Pow):
-1.12
at the temperature of:
20 °C

Additional information

A further measurement using a pH 9.0 aqueous buffer solution was attempted. In this case, the test item was not detected in the n-octanol phase and the n-octanol / aqueous buffer pH9 partition coefficient could not be calculated.