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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)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EPA OPPTS 830.7550 (Partition Coefficient, n-octanol / H2O, Shake Flask Method)
Deviations:
no
GLP compliance:
yes
Type of method:
shake-flask method to: flask method
Partition coefficient type:
octanol-water
Analytical method:
high-performance liquid chromatography
Key result
Type:
log Pow
Partition coefficient:
-2.71
Temp.:
25 °C
pH:
>= 8.04 - <= 8.73
Details on results:
The feasibility trial at a 1:1 n-octanol/water volume ratio yielded a mean estimated partition coefficient of 0.00187 (log (Pow) = -2.73). Based on these results, it was concluded that n-octanol to water volume ratios of 1:1, 2:1 and 1:2 would be appropriate for use in the definitive test.
The stock solution of D-Mannose in reagent water saturated with n-octanol used to fortify the definitive partition samples had a mean measured concentration of 3.18 mg a.s./mL (n = 3), which corresponded to 106% of the nominal D-Mannose concentration.

Prior to the definitive test, the measured pH of the aqueous partition phase (reagent water saturated with n-octanol) was 8.04. The measured pH value of the aqueous phase from a selected partition sample was 8.73.
The total mass recovered was calculated for each of the six definitive test vessels. Mass balance was obtained for D-Mannose in all vessels. The overall mean percent recovery for D-Mannose for the six partition test vessels was 107 ± 13%. The 1:2 ratio partition samples had higher mass balances than the partition samples from the other two ratios possibly due to a fortification/dilution error, however the Pow results agreed with the other two ratios.
Partition coefficients were calculated from the measured concentrations of D-Mannose in each phase for each of six samples. Overall mean n-octanol/water partition coefficients and overall mean of the logarithm (base 10) of the n-octanol/water partition coefficients were calculated for each of the six samples. The mean Pow values for D-Mannose at n-octanol/water solvent ratios of 1:1, 1:2 and 2:1 were determined to be 0.00214, 0.00168 and 0.00204, respectively. The corresponding mean log (Pow) values were -2.67, -2.78 and -2.69, respectively. The overall mean log (Pow) was -2.71 ± 0.065 (n = 6).

Measured Concentrations and Partition Coefiicient Results of the n-Octanol/Water Partition Coefficient Definitive Test with D-Mannose

Sample ID1

Solvent Ratio2

Measured Concentration (M)

Pow

Mean Pow

Log Pow

Mean Log Pow

1-oct

1:1

1.24x10-5

0.00241

0.00214

-2.62

-2.67

1-aq

5.15x10-3

2-oct

1:1

1.06x10-5

0.00187

-2.73

2-aq

5.66x10-3

3-oct

1:2

7.83x10-6

0.00158

0.00168

-2.80

-2.78

3-aq

4.95X10-3

4-oct

1:2

9.21C10-6

0.00177

-2.75

4-aq

5.21x10-3

5-oct

2:1

1.61x10-5

0.00191

0.00204

-2.72

-2.69

5-aq

8.44x10-3

6-oct

2:1

1.78x10-5

0.00217

-2.66

6-aq

8.22x10-3

Overall Mean:

0.00195

 

-2.71

 

Standard Deviation:

0.00030

 

0.065

 

% RSD

15

 

2.4

 

1“oct” = n-octanol phase and “aq” = aqueous phase of a given test system.

2Expressed as the volume ratio of n-octanol to water.

Conclusions:
This study and the conclusions which are drawn from it fulfil the quality criteria (validity, reliability, repeatability).
The overall mean n-octanol/water partition coefficient of D-Mannose at 25ºC in reagent water was 0.00195 corresponding to a log (Pow) of -2.71 ± 0.065 (n = 6, %RSD = 2.4%).
Executive summary:

A study was performed to determine the n-octanol/water partition coefficient of the test substance using the HPLC method in accordance with OECD guideline 107. The n-octanol/water partition coefficient of D-Mannose was determined in reagent water (unbuffered at neutral pH) using the flask-shaking method. The method consisted of shaking the solute (D-Mannose) with the two immiscible solvents (n-octanol and reagent water) at 25°C for a minimum of 25 minutes and analyzing the n-octanol and aqueous phases for the solute concentration using HPLC/UV and LC/MS/MS. Partition coefficients were calculated from the measured concentrations of D-Mannose in each phase for each of six samples. Overall meann-octanol/water partition coefficients and overall mean of the logarithm (base 10) of then-octanol/water partition coefficients were calculated for each of the six samples. The mean Pow values for D-Mannose atn-octanol/water solvent ratios of 1:1, 1:2 and 2:1 were determined to be 0.00214, 0.00168 and 0.00204, respectively. The corresponding mean log (Pow) values were -2.67, -2.78 and -2.69, respectively. The overall mean log (Pow) was -2.71 ± 0.065 (n = 6).

Description of key information

OECD Guideline 107

Key value for chemical safety assessment

Log Kow (Log Pow):
-2.71
at the temperature of:
25 °C

Additional information

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