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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:
8 September 2003 to 13 November 2003
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Study conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results.
Qualifier:
according to guideline
Guideline:
EPA OPPTS 830.7550 (Partition Coefficient, n-octanol / H2O, Shake Flask Method)
Qualifier:
according to guideline
Guideline:
OECD Guideline 107 (Partition Coefficient (n-octanol / water), Shake Flask Method)
Principles of method if other than guideline:
Not applicable.
GLP compliance:
yes
Type of method:
shake-flask method to: flask method
Partition coefficient type:
octanol-water
Analytical method:
gas chromatography
Key result
Type:
log Pow
Partition coefficient:
4.43
Remarks on result:
other: Temperature and pH values have not been provided, and therefore not reported
Details on results:
DETERMINATION OF THE n-OCTANOL/WATER PARTITION COEFFICIENT
The n-octanol/water partition coefficient of DBS was determined by quantifying DBS using each of the three primary components present in the test substance and reporting the Pow for DBS as a function of the respective component. Results were based upon duplicate samples prepared at three n-octanol to water solvent ratios (1:5, 1:10 and 1:20).

The mean log Pow values for DBS as a function of the dibromostyrene constituent at n-octanol to water solvent ratios of 1:5, 1:10 and 1:20 were 4.40, 4.43 and 4.47, respectively. The individual log Pow values obtained from the three solvent ratios investigated were within experimental variance of one another (± 0.3 units) and were thus statistically equivalent. The n-octanol/water partition coefficient was calculated as the mean log Pow for the six samples and was determined to be 4.43 ± 0.0567. Mass balance was calculated for DBS using the dibromostyrene constituent and quantitative recoveries were obtained in each of the six samples prepared. Recoveries ranged from 101 to 113% of the nominal DBS concentration with a mean percent recovery of 107 ± 4.64%.

The mean log Pow values for DBS as a function of the monobromostyrene constituent at n-octanol to water solvent ratios of 1:5, 1:10 and 1:20 were 3.87, 4.00 and 3.95, respectively. The individual log Pow values obtained from the three solvent ratios investigated were within experimental variance of one another (± 0.3 units) and were thus statistically equivalent. The n-octanol/water partition coefficient was calculated as the mean log Pow for the six samples and was determined to be 3.94 ± 0.678. Mass balance was calculated for DBS after correcting for a 49.0% procedural recovery of the monobromostyrene constituent in the matrix fortification sample. Procedurally corrected recoveries ranged from 99.4 to 107% of the nominal DBS concentration with a mean percent recovery of 103 ± 3.19%.

The mean log Pow values for DBS as a function of the tribromostyrene constituent at n-octanol to water solvent ratios of 1:5, 1:10 and 1:20 were 4.47, 4.51 and 4.61, respectively. The individual log Pow values obtained from the three solvent ratios investigated were within experimental variance of one another (± 0.3 units) and were thus statistically equivalent. The n-octanol/water partition coefficient was calculated as the mean log Pow for the six samples and was determined to be 4.53 ± 0.0836. Mass balance for DBS was calculated for the tribromostyrene constituent and quantitative recoveries obtained in each of the six samples prepared. Recoveries ranged from 103 to 118% of the nominal DBS concentration with a mean percent recovery of 109 ± 6.11%.

Matrix Blank and Fortification Samples

"One matrix blank sample, consisting of reagent grade water (presaturated with n-octanol), was analyzed to determine possible interferences. No interferences were observed at or above the LOQ during the sample analysis...One matrix fortification sample consisting of reagent grade water (presaturated with n-octanol) was analyzed to assess method efficiency. The sample was fortified at a nominal concentration of 100 μg DBS/L using a stock solution of DBS prepared in acetonitrile. The matrix fortification sample was
analyzed concurrently with the samples and yielded a recovery of 88.7% and 98.3% of the DBS nominal concentration based on the dibromostyrene and tribromostyrene components, respectively. Sample concentrations for DBS based on the dibromostyrene and tribromostyrene components were not corrected for procedural recovery. The recovery of DBS based on the monobromostyrene component was only 49.0% of the nominal test substance concentration due to limitations on the extractability of monobromostyrene from n-octanol saturated water using hexane extraction solvent. After consulting with the Sponsor, sample concentrations for DBS based on the monobromostyrene component were corrected for the low (49.0%) procedural recovery..."

No further information required.

Conclusions:
The n-octanol/water partition coefficient of DBS as a function of the dibromostyrene component, expressed as its logarithm (base 10), was determined to be 4.43 ± 0.0567, CV = 1.28%.

The n-octanol/water partition coefficient of DBS as a function of the monobromostyrene component, expressed as its logarithm (base 10) was determined to be 3.94 ± 0.0678, CV = 1.72%.

The n-octanol/water partition coefficient of DBS as a function of the tribromostyrene component, expressed as its logarithm (base 10) was determined to be 4.53 ± 0.0836, CV = 1.85%.
Executive summary:

The n-octanol/water partition coefficient of dibromostyrene was determined in a study following OCED Guideline 107 by monitoring the three primary components present in the test material and reporting the Pow of dibromostyrene (DBS) as a function of the respective component. Results were based upon duplicate samples prepared at three n-octanol to water solvent ratios (1:5, 1:10 and 1:20). The n-octanol/water partition coefficient of DBS as a function of the dibromostyrene component, expressed as its logarithm (base 10) was determined to be 4.43 ± 0.0567, CV=1.28%. The n-octanol/water partition coefficient of DBS as a function of the monobromostyrene component, expressed as its logarithm (base 10) was determined to be 3.94 ± 0.0678, CV=1.72%. The n-octanol/water partition coefficient of DBS as a function of the tribromostyrene component, expressed as its logarithm (base 10) was determined to be 4.53 ± 0.0836, CV=1.85%

Description of key information

The n-octanol/water partition coefficient of DBS as a function of the dibromostyrene component, expressed as its logarithm (base 10), was determined to be 4.43 ± 0.0567, CV = 1.28%.

Key value for chemical safety assessment

Log Kow (Log Pow):
4.43

Additional information

The key study, VanHoven, R.L, Chafey, K.W. and Nixon, W.B (2003), was performed in accordance with the current guideline OECD 107 (shake flask method) and in compliance with GLP. The study was considered to be reliable and adequate for use as a standalone study for this data requirement, accordingly the study was assigned a reliability score of 1.