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Physical & Chemical properties

Partition coefficient

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Reference
Endpoint:
partition coefficient
Type of information:
experimental study
Adequacy of study:
key study
Study period:
20 Oct 2004 - 10 Nov 2004
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)
Qualifier:
according to guideline
Guideline:
other: "Test on octanol/water partition coefficient" of agricultural chemicals stipulated in the "Notification Concerning test Data for Registration of Agricultural Chemicals" (12 Nohsan No. 8147: November 24, revision December 10, 2002)
GLP compliance:
yes
Remarks:
“Standards for Proper Implementation of Toxicological Studies on Agricultural Chemicals” stipul. in “Notification Concerning Proper Implementation of Toxicological Studies on Agricultural Chemicals” (11 Nohsan No. 6283: Oct 1, 1999, revision Dec 27, 2002)
Type of method:
flask method
Partition coefficient type:
octanol-water
Analytical method:
high-performance liquid chromatography
Key result
Type:
log Pow
Partition coefficient:
1.9
Temp.:
25 °C
pH:
2
Remarks on result:
other: since the pKa of the test substance is 3.2, hydrochloride buffer solution (pH 2.0) was used to suppress dissociation of the substance
Type:
Pow
Partition coefficient:
76.6
Temp.:
25 °C
pH:
2
Remarks on result:
other: since the pKa of the test substance is 3.2, hydrochloride buffer solution (pH 2.0) was used to suppress dissociation of the substance
Key result
Type:
log Pow
Partition coefficient:
ca. 1
Temp.:
25 °C
pH:
4
Remarks on result:
other: log D (pH 4), partition coefficient of the partly ionized substance at pH 4 (calculated by the applicant from log Pow (un-ionized), pKa and pH, see field Applicant's summary and conclusions)
Key result
Type:
log Pow
Partition coefficient:
ca. -1.9
Temp.:
25 °C
pH:
7
Remarks on result:
other: log D (pH 7), partition coefficient of the partly ionized substance at pH 7 (calculated by the applicant from log Pow (un-ionized), pKa and pH, see field Applicant's summary and conclusions)
Key result
Type:
log Pow
Partition coefficient:
ca. -3.9
Temp.:
25 °C
pH:
9
Remarks on result:
other: log D (pH 9), partition coefficient of the partly ionized substance at pH 9 (calculated by the applicant from log Pow (un-ionized), pKa and pH, see field Applicant's summary and conclusions)

The pH was 2.0 for all samples collected from water layers.


 


Concentration of test substance in 1-octanol and water layers:





















































  Concentration after shaking [mol/L]   Concentration after shaking [mol/L]    
 No. 1-octanol layer water layer Material blance [%]
1 3.68 x 10-34.36 x 10-5100
2 3.57 x 10-34.92 x 10-5100 
32.05 x 10-32.80 x 10-5101
42.04 x 10-32.82 x 10-5101
5 1.10 x 10-31.41 x 10-5101 
6 1.10 x 10-31.45 x 10-5101 

 


Calculation of partition coefficient:
















































 No. Pow logPow

 Mean under


the same


condition



overall mean


Pow



overall mean


log Pow


1 84.4 1.9 1.9    

76.1



1.9



2 



72.6 



1.9 



3 



73.2 



1.9 



1.9    



4 



72.3 



1.9 



5 



78.0 



1.9 



1.9    



6 



75.9 



1.9 



Standard deviation: 4.64, coefficient variation: 6.1 %


Since there was no significant variation observed in the Pow value, the partition coefficient was considered to be not concentration dependent.

Executive summary:

An octanol water partion coefficient log Pow = 1.9 was determined by shake flask method according to OECD Guideline 107 for the test substance at pH 2.0 and 25.0 °C by using a hydrochloride buffer solution to suppress dissociation of the substance.

Applicant's calculation of the partition coefficient for the (partly) dissociated form at pH 4, 7 and 9:

The calculation of partition coefficient for the (partly) dissociated form, log D (pH), based on partition coefficient for neutral form is possible, if pKa for the substance is available:

For acids:   log D (pH) = log P – log [1 + 10pH-pKa]


Based on the measured log Pow = 1.9 at pH 2 and 25 °C and the measured pKa = 3.2 at 20 °C the applicant estimated following partition coefficients for the (partly) dissociated form:

log D (pH4) = 1.0

log D (pH7) = -1.9

log D (pH9) = -3.9

Description of key information

The partition coefficient log Pow = 1.9 was determined at pH 2.0 and 25 °C. Since the pKa of the test substance is 3.2, hydrochloride buffer solution (pH 2.0) was used to suppress dissociation of the substance. (OECD Guideline 107, shake flask method).

Based on the the measured partition coefficient of the unionized form at pH 2 and pKa of the substance following partition coefficients for the (partly) dissociated form are estimated:

log D (pH 4): ca. 1.0

log D (pH 7): ca.-1.9

log D (pH 9): ca. -3.9

Key value for chemical safety assessment

Log Kow (Log Pow):
1.9
at the temperature of:
25 °C

Additional information

at pH 2