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Partition coefficient

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Reference
Endpoint:
partition coefficient
Type of information:
experimental study
Adequacy of study:
key study
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)
Qualifier:
according to guideline
Guideline:
EPA OPPTS 830.7570 (Partition Coefficient, n-octanol / H2O, Estimation by Liquid Chromatography)
Qualifier:
according to guideline
Guideline:
EU Method A.8 (Partition Coefficient)
GLP compliance:
yes
Type of method:
HPLC method
Partition coefficient type:
octanol-water
Analytical method:
high-performance liquid chromatography
Type:
log Pow
Partition coefficient:
6.33
Temp.:
20 °C
pH:
ca. 6.5
Details on results:
Two combined reference standard solutions comprised of a total of seven reference substances was prepared and injected in duplicate (once near the beginning and once near the end of the HPLC sequence). The retention times for one of the reference substances in one of the combined standards, thiourea were used to determine the analytical column dead time (t0) for use in calculating capacity factors (k) of the remaining reference substances and the test substances. The mean retention time of thiourea was 1.792 minutes. Six additional reference substances contained in the combined reference standard solutions were analyzed. The capacity factors of all the reference substances were calculated based upon their retention times. Prior to initial injection of the combined reference standard, 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 10.0 mg/mL test substance solutions were sequentially injected. The test substance eluted as 35 resolved peaks on the UV detector and 15 resolved peaks on the ELSD. The mean retention times of each UV peak ranged from 1.615 minutes to 90.379 minutes, while the mean retention times of each ELSD peak ranged from detector offset corrected 1.696 minutes to 90.063 minutes. Prior to the injections of the test substance solutions, a dilution solvent blank solution was injected to identify any solvent background peaks. The capacity factors (k) of each peak were then calculated based on the corresponding retention time. The corresponding mean n-octanol/water partition coefficients (Log POW) for the test substance UV peaks were calculated to range from an unretained (< thiourea) peak to a greater than extrapolated value of 7.43, with an extrapolated overall weighted average of 6.33 ± 0.01 (N = 3, CV = 0.20%). The individual and mean retention times and n-octanol/water partition coefficients based on UV and ELSD data for the test substance were reported. The calculated weighted average log n-octanol/water partition coefficients based on UV data for the test substance were reported. The ELSD data confirmed the retention time of the highly retained peaks and was not used in subsequent calculations. The test temperature was 20-25°C.
Conclusions:
Under the chromatographic conditions specified, the test substance eluted as 35 peaks on the ultraviolet (UV) detector and 15 peaks on the evaporative light scattering detector (ELSD). The corresponding Log POW for the test substance by UV ranged from unretained (< thiourea) to a greater than extrapolated value of 7.43, with an extrapolated overall weighted average of 6.33 ± 0.01 (N = 3, CV = 0.20%).

Description of key information

OECD Guideline 117

Key value for chemical safety assessment

Log Kow (Log Pow):
6.33
at the temperature of:
20 °C

Additional information