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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:
August 10, 2016 - October 21, 2016
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 107 (Partition Coefficient (n-octanol / water), Shake Flask Method)
Deviations:
no
Principles of method if other than guideline:
Because of the chemical nature of the test item (surface-active material), neither OECD Guideline No. 117 (HPLC Method) nor OECD Guideline No. 122 (pH-metric Method) can be applied. OECD Guideline No. 107 states that for such substances, an estimation of the partition coefficient (n-octanol/water) shall be calculated on the basis of the test item solubility in the two pure solvents.
GLP compliance:
no
Type of method:
flask method
Partition coefficient type:
octanol-water
Specific details on test material used for the study:
Internal sample code: 2929564-001
Purity: 100.3% w/w
Batch number: 2510468
Analytical method:
other: flask method
Key result
Type:
log Pow
Partition coefficient:
ca. 0
Temp.:
20 °C
Remarks on result:
other: Estimated between log Pow < - 0.40 and log Pow < - 0.22

Result

Using the analytical balance, two amounts of test item, 101.6 mg and 100.9 mg respectively, were weighed into two test tubes and increasing measured volumes of n-octanolat room temperature (ca.)were added, as reported in table below:

 
Delmopinolo HCl: n-octanol solubility test.

 

Approximate solubility (g/L)

Total volume required for complete dissolution (mL)

Solubility

after 30 min.

> 1000

0.10

Complete

 

In order to obtain a more accurate value of n-octanol solubility a second test was performed.

Using the analytical balance, test item aliquots were weighed in duplicate and increasing measured volumes of n-octanolat room temperature (ca.)were added to each aliquot as indicated in the following table, until complete dissolution was obtained.

After each solvent addition, the mixture was shaken and then stored at test temperature with intermittent shaking for 30 minutes. The contents of the test tube were visually checked after 30 minutes and after 24 hours.

 

Delmopinolo HCl: n-octanol solubility test.

 

Solubility range

(g/L)

Weight

(g)

Test 1

Weight

(g)

Test 2

Volume of addition (mL)

Solubility

after 30 min.

Solubility

after 24 h

>1500

3.0058

3.0007

2.00

Incomplete

Incomplete

 

 

Therefore the test item solubility in n-octanol was estimated to be between 1000 and 1500 g/L.

Due to the test item nature it was not possible to develop an analytical method able to quantify the test substance dissolved in n-octanol to get a more precise value.

A quantification using an UV/Vis spectrometer was tried but n-octanol adsorb in the very same region in which adsorb the test item preventing this technique to be used.

An HPLC/MS method was also tried but, even if the test item was detectable with mass spectroscopy, it was not possible to find suitable chromatographic conditions, probably due to the amphiphilic test item nature.

The mass, UV/Vis spectra and HPLC/MS chromatogram of Delmopinolo HCl are presented in Figures 1, 2 and 3 (see illustration).

Therefore the experimental phase was stopped after the preliminary test.


 

The water solubility value from this is > 2500 g/L.

The test item partition coefficient can be estimated as follows:

 

                                 So          1 < x < 1.5               < 0.4  (log Pow < - 0.40)

Partition Coefficient (Pow) = ______ = ____________ =                                                                                                             

   Sw               > 2.5                    < 0.6   (log Pow < - 0.22)

 

where:

 

So = Test item solubility in n-octanol (g/L)

Sw = Test item solubility in water (g/L)

 

Conclusions:
From the obtained experimental data, it can be concluded that the Partition Coefficient (Pow) of Delmopinolo HCl Technical sample is estimated to be between < 0.4 (log Pow < - 0.40) and < 0.6 (log Pow < - 0.22) at room temperature (ca. 20°C).
Executive summary:

Partition Coefficient (Pow) of Delmopinolo HCl is estimated to be between < 0.4 (log Pow < - 0.40) and < 0.6 (log Pow < - 0.22) at room temperature (ca. 20°C)

Description of key information

Because of the chemical nature of the test item (surface-active material), neither OECD Guideline No. 117 (HPLC Method) nor OECD Guideline No. 122 (pH-metric Method) can be applied. OECD Guideline No. 107 states that for such substances, an estimation of the partition coefficient (n-octanol/water) shall be calculated on the basis of the test item solubility in the two pure solvents.

Key value for chemical safety assessment

Log Kow (Log Pow):
0.6
at the temperature of:
20 °C

Additional information

From the obtained experimental data, it can be concluded that the Partition Coefficient (Pow) of Delmopinolo HCl Technical sample is estimated to be between < 0.4 (log Pow < - 0.40) and < 0.6 (log Pow < - 0.22) at room temperature (ca. 20°C).