N, N-bis-(2-hydroxyethyl) dimethyl ammonium methane sulfonate

Partition coefficient

Link to relevant study record(s)

Reference

Endpoint:

partition coefficient

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Study initiation date: 2021-02-02;
Experimental completion date: 2021-03-30

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

reference to other study

Remarks:

Study on water solubility - due to very high water solubility but low octanol solubility of the test item, the partition coefficient n-octanol/water was determined from the solubilities in n-octanol and water.

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

European Commission Regulation (EC) No. 440/2008

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 107 (Partition Coefficient (n-octanol / water), Shake Flask Method)

Version / remarks:

1995

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of method:

flask method

Remarks:

The saturation concentration of the test item in n-octanol was determined according to the flask method, and the Pow determined from the ratio of n-octanol solubility and water solubility.

Partition coefficient type:

octanol-water

Analytical method:

other:

Key result

Type:

log Pow

Partition coefficient:

> -1.9 - <= -1.8

Temp.:

20 °C

pH:

>= 2.8 - <= 3.6

Remarks on result:

other: The pH range is based on the study on water solubility, considering the recommended test item concentration of 0.01 mol/L according to OECD 107

Details on results:

Because the test item is a (permanent) ionic liquid, there will be no relevant dependency of log Pow from pH.
See section "Any other information on results incl. tables" below.

Preliminary visual estimation of the n-octanol solubility:
Defined amounts of the test item were stirred with increasing volumes of n-octanol at room temperature and visually checked for any undissolved particles.

Added amount of test item / mg	Total amount of test item / mg	Added volume of n-octanol / ml	Total volume of n-octanol / ml	Stirring time	Appearance of mixture
8.7	8.7	2	2	1 h	not dissolved
-	8.7	8	10	55 min	dissolved
31.8	40.5	-	10	16 h 50 min	dissolved
32.8	73.3	-	10	20 h 25 min	dissolved
185.9	259.2	-	10	4 h 55 min	not dissolved (turbid and test item floating on the surface)

According to this preliminary test, the solubility of the test item in n-octanol was between 7.3 g/L and 25.9 g/L (without correction for the purity).

Calculation of the partition coefficient log POW
The partition coefficient POW may be estimated from the saturation concentrations in n-octanol and water by the following equation:
P_OW=(c_S^(n-octanol))/(c_S^water ) (1)
cS = saturation concentration in g/l

The estimated partition coefficient was calculated with the water solubility data determined in the preliminary test of project PS20200294-5 (cS > 965 g/l) and the data obtained as outlined above. It was calculated to be: log POW < -1.6.
As the test item was an ionic compound, the program KOWWIN (part of EPI Suite) could not be used for calculating the log POW of the test item.
In the main test, the partition coefficient was estimated based on the ratio of the solubilities in water and n-octanol, due to the previous calculations. The octanol solubility was determined using the flask method. The shake flask method and the HPLC method were not applicable due to the forecasted low log POW, neither allowed the ionic nature of the substance application of OECD TG 107 (see methods section for details).

Determination of the solubility in n-octanol: Flask method
The individual saturation solubility of the test item in n-octanol 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 according to equation (1).
The n-octanol was added to the weighted test item under N2-atmosphere in the glove box. Additionally, the flasks were tightly closed in the glove box using joint clamps and parafilm. The data for the evaluation are given in the table below. The n-octanol solubility was calculated from the measured and unrounded concentration values and not from the rounded values given in the table.
In the blank experiment, 0.42 g carbon/L were found. This carbon content was supposed to result mainly from n-octanol dissolved in water. A value of about 0.57 g/L resulted by converting the carbon concentration into the n-octanol concentration for the blank experiment. As the latter value agreed well with values known in literature for water solubility of n-octanol, it was subtracted from the results of the experiments (24 h to 72 h). After this subtraction, the carbon content of the experiments (24 h to 72 h) was converted into the n-octanol solubility of the test item with the molecular weight of the test item (229.0 g/mol) and the carbon content (36.67 %) (conversion factor given in the table below).

Experiment	24 h experiment	48 h experiment	72 h experiment	blank experiment (72 h)
Amount of test item / g	23.33	23.34	23.56	--
Amount of octanol / ml	180	180	180	180
Stirring time at 30 °C / h	24	48	72	72
Dilution factor	400	400	400	20
Measured carbon concentration / mg/l	17.41 / 17.39	17.42 / 17.66	17.53 / 17.84	21.1 / 21.2
Mean carbon concentration / mg/l	17.40	17.54	17.69	21.16
n-Octanol solubility / gcarbon/l	6.96	7.02	7.07	0.42*
n-Octanol solubility / gcarbon/l minus the blank value	6.54	6.59	6.65	0.00
Conversion factor	2.7	2.7	2.7	2.7
n-Octanol solubility / g/l	17.6	17.8	18.0	0.0

*) Presumably due to n-octanol dissolved in water

As the experiments (24 h to 72 h) showed a slight tendency, a fourth experiment (168 h) was carried out for verification. Since this experiment showed a lower n-octanol solubility / g_carbon/L (5.6 g/L), it was assumed that the observed tendency resulted from the experimental variability associated with the method. Therefore, and as decomposition of the test item over time cannot be ruled out the three values of the experiments (24 h, 48 h and 72 h) were used to calculate the final result of the n-octanol solubility of the test item.
The n-octanol solubility of the test item at 20 °C was determined to be 17.8 g/L (± 0.2 g/L).

Calculation of the partition coefficient log POW from the individual solubilities
In project PS20200294-5 it was determined that the test item MAT-144 was miscible with water at room temperature (T = 25.0 °C) in all tested ratios (1:1, 1:9, 9:1). The highest tested mass ratio of test item to water 9:1 is equivalent with a water solubility of 1123.2 g/L (calculated from the mass ratio and volume fraction). Accordingly, the water solubility of the test item was determined to be ≥ 1123.2 g/l.
According to the OECD 105, the water solubility of a substance is defined as the saturation mass concentration of the substance in water at a given temperature and the water solubility is expressed in mass of solute per volume of solution. Assuming the concentration of the test item is increased in water with unlimited miscibility, the volume of 1L will contain nearly solely test item whose density was determined to 1283.7 g/L (20°C) in project PS20200294-2. Therefore the theoretical water solubility of the test item must be smaller than the density of the test item (< 1283.7 g/l).
With the both assumed maximum and minimum water solubilities of the test item (≥ 1123.2 g/L and < 1283.7 g/L) and the n-octanol solubility of the test item (17.8 g/L) determined within the present project the partition coefficient POW was calculated according to formula (1).
The partition coefficient Pow of the test item was determined to be:
log Pow ≤ -1.8
log Pow > -1.9

 

 

 

Conclusions:

Log Pow (OECD 107; A.8): > -1.9 <= -1.8

Executive summary:

The n-octanol/water partition coefficient of the test item MAT-144 was determined in a reliable and valid study performed compliant with GLP according to OECD 107 (1995) as well as EU method A.8.
The test item is an ionic liquid, consisting of a permanent cation, the quaternary ammonium compound N-bis-(2-hydroxyethyl) dimethyl ammonium, and a permanent anion, i.e. methane sulfonate. According to OECD TG 107, the flask method is not applicable to ionic liquids (paragraph 7). Estimation of log Pow based on preliminary data on solubility in water and n-octanol indicated a log Pow <-1.6. Because the applicability of the HPLC method covers log Pow in the range of 0 to 6 but is not applicable for test items showing a log Pow below 0, neither the flask method nor the HPLC method could be applied for the submission substance.
However, partition coefficients of such test items can be estimated based on the ratio of their water solubility (according to OECD 105) and their octanol solubility (based on the principle of OECD 105). Accordingly, based on the ionic character of the test item together with the presumed very low n-octanol/water partition coefficient, the n-octanol solubility was determined following the principles of OECD 105 (flask method) and the log Pow of the test item calculated from the saturation concentration in water and n-octanol following EU method A.8, Appendix 1.

Within this study, a solubility of the test item in n-octanol (20 °C) of 17.8 g/L (± 0.2 g/l) was determined.
The test item MAT-144 is completely miscible with water, resulting in a water solubility between ≥ 1123.2 g/L (highest tested concentration) and < 1283.7 g/L (density at 20 °C).
From the logarithm of the ratio of octanol solubility and water solubility, the following result was obtained for log Pow:

Log Pow (OECD 107; A.8): > -1.9 <= -1.8

While the log Pow is associated with an approximate pH of 3, there will be no relevant dependency of log Pow from pH because the test item is a (permanent) ionic liquid.

Description of key information

Log Pow (OECD 107; A.8): > -1.9 <= -1.8

Key value for chemical safety assessment

Log Kow (Log Pow):

-1.8

at the temperature of:

20 °C

Additional information

The n-octanol/water partition coefficient of the test item MAT-144 was determined in a reliable and valid study performed compliant with GLP according to OECD 107 (1995) as well as EU method A.8.
The test item is an ionic liquid, consisting of a permanent cation, the quaternary ammonium compound N-bis-(2-hydroxyethyl) dimethyl ammonium, and a permanent anion, i.e. methane sulfonate. According to OECD TG 107, the flask method is not applicable to ionic liquids (paragraph 7). Estimation of log Pow based on preliminary data on solubility in water and n-octanol indicated a log Pow <-1.6. Because the applicability of the HPLC method covers log Pow in the range of 0 to 6 but is not applicable for test items showing a log Pow below 0, neither the flask method nor the HPLC method could be applied for the submission substance.
However, partition coefficients of such test items can be estimated based on the ratio of their water solubility (according to OECD 105) and their octanol solubility (based on the principle of OECD 105). Accordingly, based on the ionic character of the test item together with the presumed very low n-octanol/water partition coefficient, the n-octanol solubility was determined following the principles of OECD 105 (flask method) and the log Pow of the test item calculated from the saturation concentration in water and n-octanol following EU method A.8, Appendix 1.

Within this study, a solubility of the test item in n-octanol (20 °C) of 17.8 g/L (± 0.2 g/l) was determined.
The test item MAT-144 is completely miscible with water, resulting in a water solubility between ≥ 1123.2 g/L (highest tested concentration) and < 1283.7 g/L (density at 20 °C).
From the logarithm of the ratio of octanol solubility and water solubility, the following result was obtained for log Pow:

Log Pow (OECD 107; A.8): > -1.9 <= -1.8

While the log Pow is associated with an approximate pH of 3, there will be no relevant dependency of log Pow from pH because the test item is a (permanent) ionic liquid.