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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:
report date: 2010-02-18
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The study was conducted according to recognised guidelines.
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:
no
Type of method:
flask method
Partition coefficient type:
octanol-water
Analytical method:
high-performance liquid chromatography
Key result
Type:
Pow
Partition coefficient:
103.66
Temp.:
25 °C
pH:
5.9
Key result
Type:
log Pow
Partition coefficient:
1.98
Temp.:
25 °C
pH:
5.9
Details on results:
MEASUREMENT AND CALCULATION:
The partition coefficient (Pow) is defined as the ratio of the equilibrium concentrations of a dissolved substance in a two-phase n-octanol and water:
Pow = Cn-octanol / Cwater

Where Cn-octanol and Cwater are respectively the solute’s concentrations (mol/L) in the n-octanol and water phases.

Cn-octanol and Cwater are calculated with the calibration equation between peak area and 4-TBC concentration. The peak area represents the response of 4-TBC to the DAD at 280 nm during the chromatographic separation.

The experimental method leads to the following results for the three different volumic ratios (see Table 2). The standard deviation is calculated on the three analyses for each phase and each assay.

The pH of water before measurement is 6.8.

Table 2: Analytical results of 4-TBC in water and octanol for determination of Pow

Sample

Volumic ratio of water phase and octanol phase (Vwater / Voctanol)

Concentration in water phase

(mg/L)

±standard deviation

Concentration in octanol phase (mg/L)

±standard deviation

pH in water phase

Pow

Log Pow

Assay 1

0.51

7.10±1.63

1084.6±11.1

5.9

152.76

2.18

Assay 2

1.00

11.45±3.04

1091.4±2.5

5.9

95.32

1.98

Assay 3

1.99

18.75±1.06

1072±11.9

5.9

57.17

1.76

Assay 4

0.50

10.05±1.77

1145.4±24.4

5.9

113.97

2.06

Assay 5

1.00

7.45±4.17

1109.9±52.1

5.9

148.98

2.17

Assay 6

2.01

20.5±3.08

1101.5±21.3

5.9

53.73

1.73

  

Conclusions:
The average n-octanol/water partition coefficient (Pow) of 4-tert-butylpyrocatechol (4-TBC) is 103.66 +/- 43.12.
The decimal logarithm of n-octanol/water partition coefficient (Log Pow) is 1.98 +/- 0.20 (standard deviation).
Executive summary:

In a study (Processium, 2010), the partition coefficient was determined by HPLC method and using the shake flask method, according to the regulation (EC) n°440/2008, A.8 and the OECD Guideline n°107.

The average n-octanol/water partition coefficient (Pow) of 4-tert-butylpyrocatechol (4-TBC) is 103.66 +/- 43.12.

The decimal logarithm of n-octanol/water partition coefficient (Log Pow) is 1.98 +/- 0.20 (standard deviation).

This study is classified as acceptable and satisfies the guideline requirements for a partition coefficient study.

Description of key information

Partition coefficient: 1.98

Key value for chemical safety assessment

Log Kow (Log Pow):
1.98
at the temperature of:
25 °C

Additional information

One experimental study (Processium, 2010) with reliability 1 according to Klimisch was available and was selected as key study. Partition coefficient was determined by HPLC method and using the shake flask method, according to the regulation (EC) n°440/2008, A.8.

Data coming from peer-review handbooks were available. As the values are in the same range, they are used in a supporting approach.