[2-[[4-[(2-chloro-4-nitrophenyl)azo]phenyl]ethylamino]ethyl](2-hydroxypropyl)dimethylammonium chloride

Partition coefficient

Link to relevant study record(s)

Reference

Endpoint:

partition coefficient

Type of information:

experimental study

Adequacy of study:

key study

Study period:

July 22, 2015 - August 13, 2015

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: guideline study (EC A.8. and OECD 107)

Reason / purpose for cross-reference:

reference to other study

Qualifier:

according to guideline

Guideline:

EU Method A.8 (Partition Coefficient)

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

no

Type of method:

flask method

Partition coefficient type:

octanol-water

Analytical method:

high-performance liquid chromatography

Key result

Type:

log Pow

Partition coefficient:

0.3

Temp.:

23 °C

pH:

7

1. Preliminary visual estimation of the water solubility

In this report the data of project 20150099.05 (water solubility) was used.This preliminary visual experiment showed that the water solubility of the test item was approximately 186 g/L.

2.    Preliminary visual estimation of the n-octanol solubility

Increasing amounts of the test item were stirred with a defined volume of n-octanol and visually checked for any undissolved parts.

Table3: Results of the preliminary visual estimation of the n-octanol solubility

Added amount of test item [g]	Amount of test item (total amount) [g]	Added volume of n-octanol [mL]	Volume n‑octanol (total amount) [mL]	Stirring time [min]	Appearance of mixture
0.0087	0.0087	2	2	95	dissolved
0.6314	0.6401	3	5	30	non dissolved
--	0.6401	10	15	1050	non dissolved

The preliminary visual experiments showed that the n-octanol solubility of the test item is between 4.35 g/L and 42.67 g/L (without correction of the purity).

Calculation of the partition coefficient log P_OW

The partition coefficient P_OW may be estimated from the saturation concentrations in n-octanol and water .

The partition coefficient was calculated with the water solubility determined in project 20150099.05 (c_S = 132 g/L). It was calculated as: log P_OW < -0.5.

Due to the calculation the shake flask method was performed.

Shake flask method

According to the ECHA guidance in information requirements and chemical safety assessment, chapter R.7a the shake flask method should be performed usually at pH 7 for salts of organic compounds. Therefore the shake flask method was done in buffer solution at pH 7: KH₂PO_4,c = 0.05 mol.

A specified amount (see Table 4) of the dried test item was dissolved in 100 mL octanol (saturated with buffer). 10 mL of this solution were added to six different flasks (experiment: 1A, 1B, 2A, 2B, 3A, 3B). Subsequently different amounts of n-octanol (saturated with buffer solution) and buffer solution (pH 7, saturated with n-octanol) were added to the flasks as described in Table 4. All mixtures were shaken for several minutes at ambient temperature (23 °C). After separation of the phases, each phase was centrifuged (30 minutes at 23 °C and 15000 rpm) and the pH values of the aqueous phases were measured (for results see Table 4). For the analytical measurement the samples were prepared as described in chapter 4.4.1 and subsequently the concentrations of the test item in the different phases were determined by HPLC.

Table 4: Test conditions and results of the shake flask method

Experiment	1A	1B	2A	2B	3A	3B
Amount of test item [mg]	19.1
Concentration of the stock solution [mg/L]	191
Volume of added stock solution [mL]	10	10	10	10	10	10
Volume of added n-octanol [mL]	0	0	10	10	30	30
Volume of added buffer [mL]	20	20	20	20	20	20
Total volume of the aqueous phase [mL]	20	20	20	20	20	20
Total volume of the n-octanol phase [mL]	10	10	20	20	40	40
pH of the aqueous phase at 23 °C	7.0	7.0	7.0	7.0	7.0	7.0
Measured concentration in aqueous phase [mg/L]	1.58/1.58	1.89/1.89	1.33/1.33	1.43/1.43	0.85/0.85	0.85/0.85
Mean concentration in aqueous phase [mg/L]^1)	31.5	37.9	26.7	28.6	17.0	17.0
Measured concentration in n-octanol phase [mg/L]	1.48/1.48	1.61/1.61	0.99/0.99	1.06/1.06	0.63/0.63	0.64/0.64
Mean concentration in n-octanol phase [mg/L]^1)	73.9	80.5	49.6	53.1	31.3	32.2

¹⁾ For the mean concentration the sample preparation (dilution) was taken into account.

The given values of the concentrations in the aqueous and the n-octanol phases are mean values of two measurements.

The following partition coefficients are calculated from the measured and unrounded concentration values and not from the rounded values given in Table 4.

 

Table 5: Partition coefficients of the shake flask method at pH 7

Experiment	POW	log POW	Average log POW
1A	2.3440	0.37	0.35
1B	2.1257	0.33
2A	1.8596	0.27	0.27
2B	1.8557	0.27
3A	1.8448	0.27	0.27
3B	1.8932	0.28
Mean value (experiment 1A to 3B)			0.3
Standard deviation			<0.1

The six determined log Pow values are within a range of ± 0.3 units as requested by the guideline.

Conclusions:

The log Pow of the test item at room temperature (23 °C) is 0.3.

Executive summary:

The partition coefficient (n-octanol/water) was determined according to the “shake flask method” described in the European Commission Regulation (EC) No. 440/2008, A.8. and in the OECD Guideline 107.

The partition coefficient log P_ow of the test item at a pH of 7 at room temperature (23 °C) was determined to be:

log P_OW = 0.3

Description of key information

The partition coefficient log P_ow of the test item at a pH of 7 at room temperature (23 °C) was determined in accordance with methods EU A.8 and OECD 107. The log P_OW of the test item under the conditions of the flask method is 0.3.

Key value for chemical safety assessment

Log Kow (Log Pow):

0.3

at the temperature of:

23 °C