Quaternary ammonium compounds, C18-22 (even numbered) alkyltrimethyl, chlorides; Docosyltrimethylammonium chloride; C18-22 TMAC

Water solubility

Link to relevant study record(s)

Reference

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From November 09, 2017 to March 06, 2018

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

non-GLP

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

other: OECD 115

Version / remarks:

27 July 1995

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: EU Method A5

Version / remarks:

30 May 2008

Deviations:

no

Principles of method if other than guideline:

Below the CMC, a surfactant is considered to be thermodynamically soluble in the water; whereas above the CMC, the solubility of a surfactant in water has been exceeded and the excess surfactant aggregates to form micelles. These micelles have significantly less effect on the surface tension of a solution and are considered not to be in solution. Thus, the water solubility of a surfactant may be expressed in terms of the CMC.

GLP compliance:

no

Remarks:

The study was conducted in a facility which operates in accordance with Good Laboratory Practice principles; however no claim of GLP compliance was intended nor is made for this study

Type of method:

other: by determining the surface tension of a range of aqueous sample solutions of differing concentration

Key result

Water solubility:

ca. 4 mg/L

Conc. based on:

test mat.

Incubation duration:

ca. 17.75 h

Temp.:

20 °C

Remarks on result:

other: CMC determined

Details on results:

Please see below table.

The readings and temperatures for the sample solutions are shown in the following table:

Table1:

Concentration (mg/L)	Reading (mN/m)	Temperature (°C)
1.006 x 103	48	20
	48	20
	48	20
301.8	49.5	20
	49.5	20
	49.5	20
100.6	50.5	20
	50.5	20
	50.5	20
60.36	51	20
	51	20
	51	20
30.18	51.5	20
	51.5	20
	51.5	20
20.12	52	20
	52	20
	52	20
10.06	52	20
	52.5	20
	52.5	20
	52.5	20
6.036	53	20
	53	20
	53	20
3.018	53.5	20
	54	20
	55	20
	56	20
	56	20
	56	20
1.006	57	20
	60	20
	62	20
	62	20
	65.5	20
	66.5	20
	66.5	20
	66.5	20
0.3018	65	20
	67	20
	68	20
	69	20
	69	20
	69	20
0.1006	71.5	20
	71.5	20
	71.5	20

Mean surface tension values were based on the last three readings for a particular concentration which were considered to be constant.

Theconcentration (mg/L), log₁₀[concentration (mg/L)] and mean surface tension values for the sample solutions are shown in the following table:

Table2

Concentration (mg/L)	Log10Concentration	Mean Surface Tension (mN/m)	Solution pH
1.006x10 ^3	3.003	48	4.76
301.8	2.48	49.5	4.94
100.6	2.003	50.5	5.14
60.36	1.781	51	5.22
30.18	1.48	51.5	5.36
20.12	1.304	52	5.35
10.06	1.003	52.5	5.3
6.036	0.781	53	5.31
3.018	0.48	56	5.28
1.006	0.003	66.5	5.31
0.3018	-0.52	69	5.29
0.1006	-0.997	71.5	5.4

The plot of log₁₀[concentration (mg/L)] versus surface tension (mN/m) can be found under 'Attached background materials' :

In this graph, line 1(red) was generated from linear regression of 5 sample solution concentrations for which the surface tension was shown to be concentration dependent and line 2 (green) was generated from linear regression of 3 sample solution concentrations for which the surface tension was observed to be essentially independent of concentration. 

The intersection of these two lines gave the critical micelle concentration and was calculated by solving the two equations:

Line 1 equation:         y =- -22.0x + 66.6
Line 2 equation:         y =- -2.19x + 54.8

The sample solutions at 0.3018 and 0.1006 mg/L were not used in generating the two lines. At this concentration the surface tension was only slightly affected and was approaching that of purified water.

The CMC was determined to be 3.93 mg/L.

Conclusions:

Under the study conditions, the the CMC or water solubility of the test substance was determined to be 4 mg/L at 20.0 ± 0.5°C.

Executive summary:

A study was conducted to determined the water solubility of the test substance, based on critical micelle concentration (CMC), according to OECD Guideline 115 and EU Method A.5. Due to the surface activity of the test substance, the CMC value was considered as a water soluibility equivalent in accordance with the ECHA R.7a Guidance. Under study conditions, the CMC of the test substance was determined to be 4 mg/L at 20.0 ± 0.5°C (Envigo, 2018).

Description of key information

The water solubility of the test substance was determined based on critical micelle concentration (a water solubility equivalent of surfactant), according to OECD Guideline 115 and EU Method A.5 (Envigo, 2018).

Key value for chemical safety assessment

Water solubility:

4 mg/L

at the temperature of:

20 °C

Additional information

(CMC)