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Partition coefficient

Link to relevant study record(s)

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 P_ow 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 K_ow of the substance was determined to be 5.70.