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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:
10th August 2000 to 8th September 2000
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 117 (Partition Coefficient (n-octanol / water), HPLC Method)
Deviations:
yes
Remarks:
(the preliminary estimate of the partition coefficient of the test substance was determine using Chem-X version 2000.1; the water used was HPLC grade)
Qualifier:
according to guideline
Guideline:
EPA OPPTS 830.7570 (Partition Coefficient, n-octanol / H2O, Estimation by Liquid Chromatography)
Deviations:
yes
Remarks:
(the preliminary estimate of the partition coefficient of the test substance was determine using Chem-X version 2000.1; the water used was HPLC grade)
GLP compliance:
yes (incl. QA statement)
Type of method:
HPLC method
Partition coefficient type:
octanol-water
Analytical method:
high-performance liquid chromatography
Key result
Type:
log Pow
Partition coefficient:
5.7
Remarks on result:
other: No information on temperature is available.
Details on results:
The preliminary estimate of the Log P = 5.749.

From the HPLC data, the partition coefficient is determined by first calculating the capacity factor k' according to:
k' = (tR - t0 / t0)
where:
k' = capacity factor
tR = HPLC retention time of the reference or test substance
t0 = dead time of column as measured by unretained compound thiourea

From the Pow reference solution data, k' was calculated for each reference substance and the values for log k' form both injections were plotted against log Pow values obtained from the test method as shown in Figure 1. In the reference solution chromatograms, the reference substance thymol eluted a barely visible shoulder on the toluene peak so thymol was not used in the calculations.

From the plotted data, the linear regression parameters were calculated as:
Slope = 0.2885
Intercept = -0.8753
Correlation Coefficient (R) = 0.996

From the data for the two injections of the Pow sample solution, the average value of k' was calculated and using the log of this average value of k' and the slope and the intercept of the calibration plot, the value of log Pow for the test substance was calculated as:
Log Pow = Log k' - intercept / slope

Table 1: Reference solution data

 Compound  Log Pow  t0  tR  k'  Log k'
 Nitrobenzene  1.9  3.457  5.101  0.476  -0.323
     3.458  5.047  0.460  -0.338
 Toluene  2.7  3.457  6.627  0.917  -0.038
     3.458  6.517  0.885  -0.053
 Napthalene  3.6  3.457  7.744  1.240  0.093
     3.458  7.582  1.193  0.076
 Butylbenzene  4.6  3.457  14.052  3.065  0.486
     3.458  13.590  2.930  0.467
 Triphenylamine  5.7  3.457  24.334  6.039  0.781
     3.458  23.011  5.654  0.752
 DDT  6.2  3.457  33.635  8.730  0.941
     3.458  31.033  7.974  0.902

Table 2: Sample data

 Injection number  Component name  Retention time  k'
 1  Thiourea  3.484  
   Omite  23.937  5.871
 2  Thiourea  3.404  
   Omite  23.302  5.845
 Average k'        5.858
 Log k'        0.768
 Log Pow        5.70
Conclusions:
Under the conditions of the test, the Log Pow of the test material was determined to be 5.70.
Executive summary:

In a GLP compliant partition coefficient study conducted in accordance with standardised guideline OECD 117, the n-octanol/water partition coefficient of the test material was determined using the HPLC method. Under the conditions of the test, the Log Pow of the substance was determined to be 5.70.

Description of key information

Log Kow was determined to be 5.70; study was conducted in accordance with OECD Guideline 117; Riggs (2000c)

Key value for chemical safety assessment

Log Kow (Log Pow):
5.7

Additional information

In a GLP compliant partition coefficient study conducted in accordance with a standardised guideline, the n-octanol/water partition coefficient of the test material was determined using the HPLC method. Under the conditions of the test, the log Kow of the substance was determined to be 5.70.

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