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EC number: 617-084-5 | CAS number: 80474-45-9
Partition coefficient
Administrative data
Link to relevant study record(s)
- Endpoint:
- partition coefficient
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Study period:
- 14th April 2015 - 22nd April 2015
- Reliability:
- 1 (reliable without restriction)
- Rationale for reliability incl. deficiencies:
- guideline study
- Qualifier:
- according to guideline
- Guideline:
- EU Method A.8 (Partition Coefficient - HPLC Method)
- Deviations:
- no
- GLP compliance:
- yes
- Type of method:
- HPLC method
- Analytical method:
- high-performance liquid chromatography
- Key result
- Type:
- log Pow
- Partition coefficient:
- ca. 2.64
- Temp.:
- 20 °C
- pH:
- ca. 7.96
- Details on results:
- Mean partition coefficient result (Log Pow): 2.64
Comments:
Sample molecular weight 468.53 grams per mole. Stock solution was prepared with 1117.89 mg of sample in 300 mL octanol.
The lower aqueous layer remained as a slightly cloudy solution even after 4 days. An early eluting peak having retention of 2.8 minutes was noticed in both the aqueous and octanol layers. - Conclusions:
- Mean partition coefficient result (Log Pow): 2.64
Comments:
Sample molecular weight 468.53 grams per mole. Stock solution was prepared with 1117.89 mg of sample in 300 mL octanol.
The lower aqueous layer remained as a slightly cloudy solution even after 4 days. An early eluting peak having retention of 2.8 minutes was noticed in both the aqueous and octanol
layers. - Executive summary:
The partition coefficient (also known as distribution coefficient) is a physicochemical property of a material, which reflects the relative aqueous, and lipid solubilities and ionization behaviour. The phase distribution is independent of the concentration of dilute species.
The shake flask method is generally applicable for the determination of the Partition Coefficient (Log Pow) of a given material where the Log Pow value is expected to fall within the range –2 to +4. It is also applicable for essentially pure substances that are soluble in water and n-octanol but not applicable to surface-active materials.
The test is generally dependent on the Nernst Partition Law, which applies only at constant temperature, pressure and pH for dilute solutions of pure substances. Dissociation or association of dissolved molecules may affect the Log Pow of a material because such behaviour results in deviations from the Nernst Partition Law. Therefore it is imperative to have preliminary information on structural formula, dissociation constant, water solubility, hydrolysis and surface tension of the test material prior to the analysis.
Preliminary estimation:
The partition coefficient is appraised using computer software which uses the chemical structure to provide an estimated value.
The estimation is used:
1. To ascertain a suitable method by which the Partition coefficient of the test material can be conducted.
2. To estimate the quantity of material necessary to saturate a desired volume of octanol and water during the formal test.
3. The volume of octanol and water required to conduct the partition coefficient test.
If the estimated result is such that -2 ≤ Log Pow ≤ 4 the shake flask method is applied. The HPLC method applies where the preliminary result is such that 0 ≤ Log Pow ≤ 6. However, either method can be employed if the predicted Log Pow falls between 0 and 4 log units (0 ≤ Log Pow ≤ 4). Occasionally, where conditions apply, the flask method can be extended up to Log unit of 5. The conditions include:
1. When the concentration of specimen in either phase is less than 0.01M.
2. When sample exhibit multiple peaks and the peak assignment become very uncertain in the HPLC method.
Formal Partition Coefficient Analysis:
Generally, the lipid phase exhibits some finite solubility in the aqueous phase and vice versa. Due to this the phases of the solvent system are mutually saturated by shaking at the test temperature. The saturated mixtures are allowed to stand for about 24 hours to allow the phases to separate.
Three flasks are filled with the saturated solvents in the n-octanol to water ratio of 1:1, 1:2 and 2: 1 and labeled flask 1, 2 and 3 respectively. The total volume of the two-phase system selected such that it nearly fills the test vessel. Known quantities of sample are added to solvents in all three vessels, after which they are shaken vigorously with a laboratory shaker for about one hour.
Vigorous shaking has the tendency to produce emulsions which may sometimes not break, even after centrifugation, and there by giving incomplete Log Pow values. Therefore all three flasks are allowed to stand for over 24 hours to ensure equilibrium is reached.
The test temperature is kept constant ( 1 °C) within the range of 20 to 25°C. The pH of aqueous phase from all three test vessels is also determined. The concentration of specimen in each of the two phases, from each test vessel was determined with HPLC. The reliability of the determined values of Log Pow is tested by comparison of the means of the duplicate determinations with the overall mean.
Mean partition coefficient result (Log Pow): 2.64
Reference
Analytical Determinations:
| Flask No. | 1 | 2 | 3 | 4 | 5 | 6 |
| Solvent Ration (O:W) | 1:1 | 1:1 | 1:2 | 1:2 | 2:1 | 2:1 |
| Volume of Octanol (ml) | 45 | 45 | 30 | 30 | 60 | 60 |
| Volume of Water (ml) | 45 | 45 | 60 | 60 | 30 | 30 |
| Amount of sample added (g) | 0.168 | 0.168 | 0.112 | 0.112 | 0.224 | 0.224 |
| pH (aqueous phase) | 4.17 | 4.09 | 4.16 | 4.17 | 3.76 | 3.74 |
| Mean Peak area (aqueous phase) | 103812.0 | 99876.0 | 142459.0 | 144969.5 | 6047.0 | 7610.5 |
| Concentration (g/L) (aqueous phase) | 0.00708 | 0.00683 | 0.00955 | 0.00971 | 0.00082 | 0.00092 |
| Dilution Factor | 1 | 1 | 1 | 1 | 1 | 1 |
| Concentration (g/L) (aqueous phase) | 0.00708 | 0.00683 | 0.00955 | 0.00971 | 0.00082 | 0.00092 |
| Mean Peak area (octanol phase) | 2630289.5 | 2630566.0 | 2609938.0 | 2621125.0 | 2412671.5 | 2395798.0 |
| Concentration (g/L) | 0.16868 | 0.16870 | 0.16738 | 0.16810 | 0.15476 | 0.15368 |
| Dilution Factor | 20 | 20 | 20 | 20 | 20 | 20 |
| Concentration (g/L) (octanol phase) | 3.37365 | 3.37400 | 3.34761 | 3.36193 | 3.09525 | 3.07367 |
| Log P | 2.6782 | 2.6940 | 2.5447 | 2.5394 | 3.5747 | 3.5219 |
Description of key information
The partition coefficient (also known as distribution coefficient) is a physicochemical property of a material, which reflects the relative aqueous, and lipid solubilities and ionization behaviour. The phase distribution is independent of the concentration of dilute species.
The shake flask method is generally applicable for the determination of the Partition Coefficient (Log Pow) of a given material where the Log Pow value is expected to fall within the range –2 to +4. It is also applicable for essentially pure substances that are soluble in water and n-octanol but not applicable to surface-active materials.
The test is generally dependent on the Nernst Partition Law, which applies only at constant temperature, pressure and pH for dilute solutions of pure substances. Dissociation or association of dissolved molecules may affect the Log Pow of a material because such behaviour results in deviations from the Nernst Partition Law. Therefore it is imperative to have preliminary information on structural formula, dissociation constant, water solubility, hydrolysis and surface tension of the test material prior to the analysis.
Preliminary estimation:
The partition coefficient is appraised using computer software which uses the chemical structure to provide an estimated value.
The estimation is used:
1. To ascertain a suitable method by which the Partition coefficient of the test material can be conducted.
2. To estimate the quantity of material necessary to saturate a desired volume of octanol and water during the formal test.
3. The volume of octanol and water required to conduct the partition coefficient test.
If the estimated result is such that -2 ≤ Log Pow ≤ 4 the shake flask method is applied. The HPLC method applies where the preliminary result is such that 0 ≤ Log Pow ≤ 6. However, either method can be employed if the predicted Log Pow falls between 0 and 4 log units (0 ≤ Log Pow ≤ 4). Occasionally, where conditions apply, the flask method can be extended up to Log unit of 5. The conditions include:
1. When the concentration of specimen in either phase is less than 0.01M.
2. When sample exhibit multiple peaks and the peak assignment become very uncertain in the HPLC method.
Formal Partition Coefficient Analysis:
Generally, the lipid phase exhibits some finite solubility in the aqueous phase and vice versa. Due to this the phases of the solvent system are mutually saturated by shaking at the test temperature. The saturated mixtures are allowed to stand for about 24 hours to allow the phases to separate.
Three flasks are filled with the saturated solvents in the n-octanol to water ratio of 1:1, 1:2 and 2: 1 and labeled flask 1, 2 and 3 respectively. The total volume of the two-phase system selected such that it nearly fills the test vessel. Known quantities of sample are added to solvents in all three vessels, after which they are shaken vigorously with a laboratory shaker for about one hour.
Vigorous shaking has the tendency to produce emulsions which may sometimes not break, even after centrifugation, and there by giving incomplete Log Pow values. Therefore all three flasks are allowed to stand for over 24 hours to ensure equilibrium is reached.
The test temperature is kept constant (+/- 1 °C) within the range of 20 to 25°C. The pH of aqueous phase from all three test vessels is also determined. The concentration of specimen in each of the two phases, from each test vessel was determined with HPLC. The reliability of the determined values of Log Pow is tested by comparison of the means of the duplicate determinations with the overall mean.
Mean partition coefficient result (Log Pow): 2.64
Key value for chemical safety assessment
- Log Kow (Log Pow):
- 2.64
Additional information
Mean partition coefficient result (Log Pow): 2.64 at a temperature of 20 to 25°C
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