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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:
2017-04-10 to 2017-07-20
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 117 (Partition Coefficient (n-octanol / water), HPLC Method)
Deviations:
no
Qualifier:
according to
Guideline:
EPA OPPTS 830.7570 (Partition Coefficient, n-octanol / H2O, Estimation by Liquid Chromatography)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Type of method:
HPLC method
Partition coefficient type:
octanol-water
Analytical method:
high-performance liquid chromatography
Key result
Type:
log Pow
Partition coefficient:
> 6.5
Temp.:
40 °C
pH:
6

RESULTS AND DISCUSSION

A total of seven reference substances were prepared and injected in duplicate (once at the beginning and once near the end of the HPLC sequence). The retention times for one of the reference substances, thiourea, was used to determine the analytical column dead time (t0) for use in calculating capacity factors (k) of the remaining reference substances and the test substance. The mean retention time of thiourea was 0.849 minutes.

Six additional reference substances were analyzed. The capacity factors of all the reference substances were calculated based upon their retention times. Calculated Log k values for the reference substances are presented in Table 4.

Table 4 Reference Standards Retention Times, Capacity Factors, and Log POWValues

 

 

Reference

Standard

 

Concentration

(mg/L)

Retention Time

(minutes)

Capacity

Factor

(k)1,2

 

log k2

 

 

log POW3

 

Thiourea

10.0

0.851

0.846

N/A

N/A

N/A

Acetanilide

20.0

0.951

0.951

0.121

0.121

-0.918

-0.918

1.00

2-Nitrophenol

10.0

1.148

1.142

0.353

0.346

-0.452

-0.461

1.80

Toluene

50.0

1.822

1.820

1.147

1.145

0.0597

0.0588

2.70

Naphthalene

5.00

2.176

2.171

1.565

1.559

0.194

0.193

3.60

Fluoranthene

5.02

5.526

5.520

5.513

5.506

0.741

0.741

5.10

4’-DDT

50.0

9.886

9.863

10.651

10.624

1.027

1.026

6.50

1  Capacity factor (k) is the standard retention time minus the mean column dead time (0.849 minutes for thiourea) divided by the mean column dead time.

2  Values obtained utilizing Microsoft® Excel 2010 in full precision mode. Manual calculations may differ slightly.

3   Log POWvalues are based on literature values provided in OECD Guideline 117.

 

Before the initial injection of the reference standards, an injection of a reagent blank solution (75%:25% MeOH: H2O, v/v) showed that the reagents used were free of any contaminants and confirmed the peak retention assignments for the reference substances.

The three 0.100 mg a.i./mL test substance solutions were sequentially injected. The test substance eluted as one distinct peak on the UV detector. A fourth test substance solution at 0.500 mg a.i./mL was subsequently injected to verify that the peak was correctly attributed to the test substance. Only peaks that had an area count of greater than 5% of the total area of the test substance peaks were included in the Log POW calculations. The capacity factor (k) was calculated based on the retention times and the results for the three injections were averaged. Because the retention time was greater than the retention time of the highest Log POW standard, the corresponding Log POW value for the test substance was determined to be >6.50. The calculated mean retention time, capacity factor, and mean n-octanol/water partition coefficient for the test substance are presented in Table 5.

Table 5 Logn-Octanol/Water Partition Coefficients (Log POW) Based on UV Data for the Test Substance

 

Sample

Number

(524C-143-)

Retention

Time

(minutes)

Mean ()

Standard

Deviation (SD)1

Log POW1

Mean ()

Standard

Deviation (SD)1

 

1

2

3

22.381

22.379

22.376

= 22.379

SD = 0.0025

>6.50

>6.50

>6.50

= >6.50

SD = N/A

1Values obtained utilizing Microsoft® Excel 2010 in full precision mode. Manual calculations may differ slightly.

 


 

Conclusions:
CONCLUSIONS
Under the chromatographic conditions specified, the test substance eluted as one peak. The corresponding mean n-octanol/water partition coefficient (Log POW) for the test substance was >6.50.
Executive summary:

Under the chromatographic conditions specified, the test substance eluted as one peak on the ultraviolet (UV) detector. The

corresponding Log POW for the test substance was >6.50.

Description of key information

The octanol/water partition coefficient of the test item was determined in an experimental study performed in accordance with the following test guidelines: OECD 117, OPPTS 830.7570, Official Journal of the European Communities No. L383 Method A.8: Partition Coefficient and TSCA Title 40 of the Federal Code of Regulations, Part 796, Section 1570: Partition Coefficient (n-Octanol/Water) - Estimation by Liquid Chromatography, and GLP requirements.

Under the chromatographic conditions specified, the test substance eluted as one peak. The corresponding mean n-octanol/water partition coefficient (Log POW) for the test substance was >6.50.

Key value for chemical safety assessment

Log Kow (Log Pow):
6.5
at the temperature of:
40 °C

Additional information