Quaternary ammonium compounds, C14-18 (even numbered) and C18 unsaturated-alkyl-hydroxyethyl-dimethyl, chlorides

Water solubility

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

water solubility

Remarks:

Critical Micelle Concentration

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

30 November 2016 - 16 August 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Remarks:

The determination was performed using a procedure based on Method A.5 Surface Tension of Commission Regulation (EC) No 440/2008 of 30 May 2008 and Method 115 of the OECD Guidelines for the Testing of Chemicals, 27 July 1995.

Justification for type of information:

The study was conducted using a procedure based on an internationally recognised method, and under GLP. No deviation was reported. Test substance is adequately specified with purity. Therefore full validation applies.

Qualifier:

equivalent or similar to guideline

Guideline:

other: Method A.5 Surface Tension of Commission Regulation (EC) No 440/2008 of 30 May 2008

Qualifier:

equivalent or similar to guideline

Guideline:

other: Method 115 of the OECD Guidelines for the Testing of Chemicals, 27 July 1995.

GLP compliance:

yes (incl. QA statement)

Remarks:

UK GLP compliance programme (inspected on 05 July 2016 / signed on 28 Octobre 2016)

Type of method:

other: ring method

Key result

Water solubility:

70 mg/L

Temp.:

20 °C

Remarks on result:

other: The water solubility of a surfactant may be expressed in terms of the CMC.

Results

The surface tension readings, temperatures and pH values for the sample solutions are shown in the experimental report.

The concentration, log10 concentration and mean surface tension values for the sample solutions are shown in the following table:

Table 4.8/1.- concentration, log10 concentration and mean surface tension

Concentration (mg/L)	log10 Concentration	Mean Surface Tension (mN/m)
1.00 x 103	3.00	45.1
502	2.70	42.6
301	2.48	42.4
181	2.26	43.4
100	2.00	44.6
40.1	1.60	48.4
24.1	1.38	55.3
15.1	1.18	59.3
10.0	1.00	62.6
4.01	0.603	63.3
1.00	1.30 x 10-3	66.4

The plot of surface tension (mN/m) versus log10 [concentration (mg/L)] is shown in the experimental report.

Equation line 1 (red): y = -23.3 · x + 86.5

Equation line 2 (green): y = 0.215 · x + 43.1

Line 1 (red) in the plot was generated from linear regression of 4 sample solution concentrations for which the surface tension was shown to be concentration dependent and Line 2 (green) in the plot was generated from linear regression of 5 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 to be 70.0 g/L.

Discussion

The critical micelle concentration (CMC) test was performed due to the surface active nature of the test item, determined in Section 4.10. The CMC is an important characteristic of a surfactant. At low concentrations of surfactant, the surface tension of water is only slightly affected. When increasing the concentration but before reaching the CMC, the surface tension changes significantly. After reaching the CMC and above, the surface tension remains relatively constant or changes with a much more gradual slope.

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.

Conclusions:

The critical micelle concentration of the test item was determined to be 70.0 mg/L at 20.0 ± 0.5 °C.

Executive summary:

A GLP determination was performed by a ring method, using a procedure based on Method A.5/OECD115.

The critical micelle concentration (CMC) test was performed due to the surface active nature of the test item, determined in Section 4.10.

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.

The concentrations of the test item tested were: at 1.00g/L, 502, 301, 181,100, 40.1, 24.1, 15.1,10.0, 4.01 and 1.00 mg/L.

The mean surface tension value for each sample solution was calculated from readings on the apparatus that were considered to be on a consistent data plateau.

The critical micelle concentration (CMC) was calculated from the interception of the two lines of best fit plotted on the surface tension versus log concentration graph, specifically the concentration dependent and non-concentration dependent regions.

The water solubility of a surfactant may be expressed in terms of the CMC.

The critical micelle concentration of the test item was determined to be 70.0 mg/L at 20.0 ± 0.5 °C.

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.

Reference 2

Endpoint:

water solubility

Data waiving:

study technically not feasible

Justification for data waiving:

other:

Justification for type of information:

JUSTIFICATION FOR DATA WAIVINGNo experimental determination was possible according to Method A.6 Water Solubility of Commission Regulation (EC) No 440/2008 of 30 May 2008, Method 105 of the OECD Guidelines for Testing of Chemicals, 27 July 1995, or Method 830.7840 of the OCSPP Guidelines (formerly OPPTS Guidelines), March 1998, due to the surface active nature of the test item.A preliminary test to estimate the water solubility of the test item was attempted; however, the excess of test item in the sample solution could not be separated out and testing had to be aborted. It was then agreed with the Sponsor that measuring the critical micelle concentration (Please see support study) was more appropriate for this test item.

Description of key information

Water solubility (waiving): surface active substance.

The critical micelle concentration of the test item was determined to be 70.0 mg/L at 20.0 ±0.5 °C (experimental study). The water solubility limit of a surfactant may be expressed in terms of the CMC.

Key value for chemical safety assessment

Water solubility:

70 mg/L

at the temperature of:

20 °C

Additional information

Water solubility (waiving): no experimental determination was possible according to Method A.6 /105 due to the surface active nature of the test item. A preliminary test to estimate the water solubility of the test item was attempted; however, the excess of test item in the sample solution could not be separated out and testing had to be aborted.

The critical micelle concentration (CMC) (experimental study): a test was performed by a ring method at several concentrations based on A5/OECD 115 due to the surface active nature of the test item, determined in Section 4.10.

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 limit of a surfactant may be expressed in terms of the CMC.