Disodium tartrate

Partition coefficient

Link to relevant study record(s)

Reference

Endpoint:

partition coefficient

Type of information:

experimental study

Adequacy of study:

key study

Study period:

17 November-11 December 2015

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

Partition coefficient of the test item was calculated based on the ratio of its water solubility and its octanol solubility (based on OECD 105).

Qualifier:

equivalent or similar to guideline

Guideline:

other: Based on determination of ratio n-octanol solubility vs. aqueous solubility. Solubility determination accordingto OECD guideline 105, determination of octanol solubuility based on principle of OECD guideline 105.

Qualifier:

according to guideline

Guideline:

EU Method A.8 (Partition Coefficient - Shake Flask Method)

Principles of method if other than guideline:

Estimation based on determination of individual solubilities in n-octanol and water. The individual solubities are conducted according to guideline EU Method A.6 and OECD guideline 105 for water solubilities and based on these guidelines for n-octanol solubility determination.

GLP compliance:

no

Type of method:

other: Based on determination of ratio n-octanol solubility vs. aqueous solubility. Solubility determination accordingto OECD guideline 105, determination of octanol solubuility based on principle of OECD guideline 105.

Partition coefficient type:

octanol-water

Specific details on test material used for the study:

Storage conditions: ambient temperature (10 to 30 °C)

Analytical method:

other: atomic absorption spectroscopy (AAS)

Key result

Type:

log Pow

Partition coefficient:

-4.5

Temp.:

20 °C

Remarks on result:

other: pH was not controlled

Results and method

Defined amounts of the test item were stirred with increasing volumes of n-octanol at room temperature and visually checked for any undissolved parts.

Table 1: Results of the preliminary visual estimation of the n-octanol solubility

Amount of test item /mg	Added volumeof n-octanol / mL	Total volume of n-octanol /mL	Stirring time /h	Appearance of mixture
7.5	1	1	2	Not dissolved
	9	10	19	Not dissolved
	90	100	3.5	Not dissolved

According to this preliminary test the solubility of the test item in n-octanol is at least below 0.075 g/L (without correction for the purity).

  Calculation of thepartition coefficient logP_ow from the preliminary test

The partition coefficient Pow may be estimated from the saturation concentrations in n-octanol and water by the following equation:

P_OW = Cs_octanol/Cs_water (1)

where, cs= saturation concentration in g/L

The estimated partition coefficient was calculated with the water solubility data determined in the preliminary test in test reoport reference [4.8 -1] (Cs= 200 g/L) and the data reported above. It was calculated to be: log Pow< -3.4.

 

  Determination of the solubility in n-octanol: Flask method

The individual saturation solubility of the test item in n-octanol, based on the flask method described in the OECD guideline 105, was performed within this study. After that, the partition coefficient was estimated based on the ratio of the test item solubility in n-octanol and water (determined in test report reference [4.8 -1]) according to equation (1).

The data for the evaluation are given in Table 2.

Table 2: n-Octanol solubility experiments of the test item

Experiment	24 h experiment	48 h experiment	72 h experiment	blank experiment (72 h)
Amount of test item / mg	13.9	12.0	11.7	-
Amount of octanol / mL	30	30	30	30
Stirring time at 30 °C / h	24	48	72	72
Measured concentration sodium / mg/L	3	2	1	1
n-Octanol solubility / mg/L	15	10	5	5

The results of the n-octanol solubility showed a standard deviation of 50% and the result of the blank experiment was in the same order of magnitude. As a conservative approach the highest solubility was taken as final result. The maximum n-octanol solubility of the test item at 20 °C was determined to be 15mg/L. 

Calculation of the partition coefficient logP_ow from the individual solubilities

In the test report reference [4.8 -1] the water solubility of the test item at 20 °C was determined to be 500 g/L. Within this project the n-octanol solubility of the test item at 20 °C was determined to be 15 mg/L.

The partition coefficient Pow was estimated from the individual solubility in n-octanol and water by the equation (1).

The partition coefficient Pow of the test item was determined to be:

logPow = -4.5

The results of the n-octanol solubility showed a standard deviation of 50%.However it can assumed that the n-octanol solubility of the test item is in any case considerably lower than its water solubility and hence the logPow will be <0.

Description of key information

log P_OW= -4.5 at 20 °C ( Partition coefficient of the test item was calculated based in the ratio of its water solubility and its octanol solubility (based on OECD 105))

Key value for chemical safety assessment

Log Kow (Log Pow):

-4.5

at the temperature of:

20 °C

Additional information

The partition coefficient of the test substance is estimated based on the ratio of its water solubility and octanol solubility, because the available test methods are not applicable for substance, which has a logPow value lower than -2.