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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:
6 January 2012 - 10 March 2012
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other:
Remarks:
This study was considered as reliable with restrictions because it was not conducted under GLP and there are some lack of details in the study report.
Reason / purpose:
reference to same study
Reason / purpose:
reference to other study
Reference:
Composition 0
Qualifier:
according to
Guideline:
EU Method A.8 (Partition Coefficient)
Deviations:
no
Qualifier:
according to
Guideline:
OECD Guideline 117 (Partition Coefficient (n-octanol / water), HPLC Method)
Version / remarks:
(13 April 2004)
Deviations:
no
GLP compliance:
no
Type of method:
HPLC method
Partition coefficient type:
octanol-water
Test material information:
Composition 1
Analytical method:
high-performance liquid chromatography
Key result
Type:
log Pow
Partition coefficient:
ca. 3.09
Temp.:
30 °C
pH:
ca. 6.5
Remarks on result:
other: +/- 0.01

Reference items:

Retention times and capacity factors

The retention times of the reference items are presented in the following table.

tR1(min) tR2(min) tR3 (min)  Mean (min) Relative standard deviation
Test item  5.87  5.91 5.88 5.89  0.35%
Dead time  2.58  2.59  2.56  2.58  0.59%

log Pow / log k

The calculated values for the test item are presented in the following table.

 
 Measurement No.  k  log k  log Pow
 1  1.28 0.11  3.08 
 2 1.28  0.11  3.09 
 3 1.30  0.11  3.10 
 Mean      3.09
 Standard deviation      0.01

log Pow is calculated using the regression equation obtained from the reference items.

log Pow = (log k + 1.072) / 0.382

Results obtained with another HPLC Column

The retention times capacity factors of the reference items obtained with a different C18 bonding are presented in the table below.

 
 Compound  tR (min)  k log k 
 Benzene  4.09 0.86  -0.07 
 Trichloroethylene  5.11 1.32  0.12 
 Toluene 5.61  1.55  0.19 
 M-Xylene 8.33  2.79  0.45 
 1,2,4 trimethyl benzene 12.17  4.53  0.66 
 Benfuracarb  20.19  8.18  0.91
Butralin   37.35 15.98  1.20 
 Heptachlor  47.45 20.57  1.31 

The linear regression of the plot log k versus log Pow gives the following equation:

log k = (0.424 x log Pow) - 0.919

with a coefficient of determination r2 = 0.993

The retention time of the test item was 7.97 min, corresponding to a log k of 0.42. According to the previous equation, the log Pow can be estimated to 3.16 with this column.

This result is not significantly different from the one obtained previously (3.09). It can be concluded that a change in the C18 silica bonding chemistry has not significant effects on log Pow results.

Conclusions:
Using the HPLC method, log Pow was determined for NOPOL.

Mean retention time: 5.89 min
log Pow: 3.09 +/- 0.01

This value is the mean +/- standard deviation of three independant determinations.
Executive summary:

The purpose of the study was to determine the partition coefficient n-octanol / water (log Pow) of NOPOL using HPLC (High Performance Liquid Chromatography).

The study was performed using the HPLC method. Eight reference items with different retention times were used to produce the calibration curve. They were chosen in relation to the expected retention time of the test item. For each reference item, two determinations were performed. The capacity factor k was calculated from the retention time of acetone (dead time) and the retention time of the respective reference item. A calibration function (log k versus log Pow, linear fit) was determined based on literature values of Pow for the reference items.

Using the calibration function log k versus log Pow, the following log Pow was determined for NOPOL:

Mean retention time: 5.89 min

log Pow: 3.09 + 0.01

This value is the mean + standard deviation of three independant determinations.

Description of key information

The partition coefficient was determined by the HPLC method.
The partition coefficient log Pow of nopyl acetate is 3.09 ± 0.01.

Key value for chemical safety assessment

Log Kow (Log Pow):
3.09
at the temperature of:
30 °C

Additional information

Key study conducted by the High Performance Liquid Chromatographic method according to OECD 117 Guideline and EU Method A8 without any deviation. Therefore, this value can be used as key value.