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Physical & Chemical properties

Partition coefficient

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Description of key information

The test substance, NBPT, was determined to have an overall mean octanol/water partition coefficient of 2.78 ± 0.05. The mean log Pow was 0.444 with an absolute standard deviation of 0.008.

Key value for chemical safety assessment

Log Kow (Log Pow):
0.444
at the temperature of:
20 °C

Additional information

Introduction:

The purpose of this study was to determine the n-octanol/water partition coefficient of the test substance, Butyl Phosphorothioic Triamide (NBPT). The study was conducted as described in the ABC study protocol and alterations entitled "Determination of n-Octanol/Water Partition Coefficient (Shake Flask Method) for Butyl Phosphorothioic Triamide (NBPT)", which were patterned after the Official Journal of the European Communities, Part A.8, Methods for the determination of Physico-Chemical Properties, Partition Coefficient. The study was conducted in compliance with the GLP standards of the OECD.

Results:

Preliminary Test results:The results of the preliminary test indicated that the octanol and aqueous phases were at equilibrium after 24 hours.The partition coefficient, Pow, was determined to be 2.74, 2.88, 2.69, and 2.73, for the 2, 4, 22, and 24 hour sampling points, respectively. The corresponding Log Pow values were 0.437, 0.459, 0.430, and 0.436, respectively. Based on the small change in Pow, the test substance was determined to reach equilibrium after 24 hours shaking, the approximate Log Pow was 0.44, and the 2: 1 ratio of octanol to aqueous was sufficient to quantitate the amount of NBPT in both phases.

Definitive Test Results:The definitive test was conducted at 20 ± 1°C and utilized three volume different ratios of octanol to water (4: 1, 2: 1, and 1:1). The standard curves used for the qualltitation of the test substance in the aqueous and octanol phases showed linearity, with a correlation coefficient value of 0.99997. The mean Log Pow of NBPT in the three volume ratios (octanol to aqueous) of 4:1, 2:1, and 1:1 was determined to be 2.75, 2.75, and 2.82, respectively, which corresponded to Log Pow values of 0.440, 0.439, and 0.450, respectively.

Conclusion:

The test substance, NBPT, was determined to have an overall mean octanol/water partition coefficient of 2.78 ± 0.05. The mean log Pow was 0.444 with an absolute standard deviation of 0.008.