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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:
04 May to 17 August 2012
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Study conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results. The study report was conclusive, with experiments conducted according to appropriate and valid guidelines and conducted under GLP conditions.
Qualifier:
according to guideline
Guideline:
EU Method A.8 (Partition Coefficient)
Deviations:
no
Qualifier:
according to guideline
Guideline:
OECD Guideline 117 (Partition Coefficient (n-octanol / water), HPLC Method)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EPA OPPTS 830.7570 (Partition Coefficient, n-octanol / H2O, Estimation by Liquid Chromatography)
Deviations:
no
GLP compliance:
yes
Type of method:
HPLC method
Partition coefficient type:
octanol-water
Analytical method:
high-performance liquid chromatography
Key result
Type:
Pow
Partition coefficient:
140
Temp.:
35 °C
Remarks on result:
other: Temperature ± 1ºC. The pH was not reported.
Key result
Type:
log Pow
Partition coefficient:
2.1
Temp.:
35 °C
Remarks on result:
other: Temperature ± 1ºC. The pH was not reported.
Details on results:
PRELIMINARY STUDY
Calculation of the Pow, Rekker method: The Pow of the test material was calculated to be 8.1 (log Pow 0.91).
Calculation of pKa: No pKa values for acidic and basic groups in the molecular structure of the test material in the logarithm range of 1 - 14 were calculated.

MAIN STUDY
HPLC results:
In the chromatogram of the test material, one test material peak was observed.
The results of the HPLC method are given in the Table 2.

Table 2. Pow of the Test Material and Reference Substances

Substance

tr,1 (min)

tr,2 (min)

Mean tr (n=2)

Log Pow

Pow

Formamide (t0)

1.150

1.151

1.151

 

 

Ethylmethylketone

1.373

1.373

 

0.3

 

Benzylalcohol

1.451

1.453

 

1.1

 

Nitrobenzene

1.935

1.937

 

1.9

 

Toluene

3.184

3.187

 

2.7

 

Bromobenzene

3.357

3.386

 

3.0

 

1,4-Dichlorobenzene

4.120

4.123

 

3.4

 

Test Material

2.167

2.167

2.167

2.1

1.4 x 10²

Conclusions:
Under the conditions of the test, the partition coefficient of the test material was determined to be Pow 1.4 x 10² and log Pow 2.1, using the HPLC method.
Executive summary:

The partition coefficient of the test material was determined using the HPLC method performed in accordance with GLP and to the standardised guidelines OECD 117, EU method A.8 and EPA OPPTS 830.7570.

The partition coefficient was first calculated in a preliminary test by the Rekker method to be Pow 8.1, log Pow 0.91. No pKa values for acidic and basic groups in the molecular structure of the test material were calculated using the Perrin calculation method in the logarithm range of 1 - 14. Based on the calculation it was decided to perform the HPLC method at neutral pH for an accurate determination of the Pow.

Under the conditions of the test, the partition coefficient of the test material was determined to be Pow 1.4 x 10² and log Pow 2.1.

Description of key information

The partition coefficient of 3,5-Dimethylpyrazole was determined to be Pow 1.4 x 10^2 and log Pow 2.1, in a key study (Baltussen, 2012) performed according to OECD 1147, EU method A.8 and EPA OPPTS 830.7570. A QSAR prediction has also been included as supporting data.

Key value for chemical safety assessment

Log Kow (Log Pow):
2.1
at the temperature of:
35 °C

Additional information

The partition coefficient of the test material has been addressed by providing one key and one supporting study.

Baltussen (2012) has been provided as the key study, where the partition coefficient was determined to be Pow 1.4 x 10² and log Pow 2.1 using the HPLC method. The study was performed in line with GLP and standardised guidelines and had thus been assigned a reliability score of 1 using the principles for assessing data quality as set out in Klimisch (1997).

A prediction made using the KOWWIN (v 1.68) model within the QSAR EPISuite has been provided as supporting data. The test material was predicted to have a partition coefficient of log Pow 1.15. The prediction has been assigned a reliability score of 4, according to the principles of Klimisch (1997).