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Water solubility

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2018-02-20

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: ISO 304:1985: Surface active agents -- Determination of surface tension by drawing up liquid films

Deviations:

no

Principles of method if other than guideline:

The surface tension of a solution of surfactant generally decreases with increasing concentration until the CMC is achieved. At higher concentration, the surface tension remains essentially unchanged. In a graph of the surface tension as a function of concentration, points form normally two straight lines with different slopes. The CMC is given by the intersection of the two straight lines.

GLP compliance:

no

Type of method:

other: critical micelle concentration (CMC)

Key result

Water solubility:

0.08 g/L

Conc. based on:

test mat.

Incubation duration:

15 min

Temp.:

20 °C

pH:

7.16

Remarks on result:

other: Critical micelle concentration

Experiment 1

Concentration (g/L)	0.00114	0.0037	0.00582	0.0106	0.0206	0.0438	0.2418	0.4841	1.016
Surface tension (mN.m)	71.2	64.1	57.2	52.7	53.6	41.4	32.9	31.8	31.4

 

Experiment 2

Concentration (g/L)	0.00102	0.00369	0.00591	0.01192	0.02383	0.2390	0.51243	1.04439
Surface tension (mN.m)	71.2	60.2	55.4	50.0	45.7	32.8	31.9	30.9

 

Experiment 3

Concentration (g/L)	0.00359	0.00459	0.01138	0.02311	0.04777	0.124692	0.4650	0.96348
Surface tension (mN.m)	65.2	63.6	61.8	50.1	41.7	33.9	32.6	31.4

 

 

Curve	Straight line 1	Straight line 2	CMC (g/L)	Average	Standard deviation
1	y = -8.85 ln(x) + 12.076	y = -1.039 ln(x) + 31.296	0.085	0.08	0.01
2	y = -8.227 ln(x) + 14.074	y = -1.287 ln(x) + 30.984	0.087
3	y = -9.167 ln(x) + 12.133	y = - 2.59ln(x) + 31.36	0.073

 

Conclusions:

The critical micelle concentration was determined to be 0.08 ± 0.001 g/L at 20 °C.

Executive summary:

A study was conducted to determine critical micelle concentration (CMC) of the test item in water. The substance is a surfactant and thus the determination of the water solubility was technically not feasible. Upon reaching CMC, any further addition of test item will just increase the number of micelles. Below the CMC concentration the test item only individual surfactant molecules are present. Using the plate method to determine the surface tension, three individual experiments were performed to determine the surface tension as a function of the test item concentration. The functions of the two curves above and below the CMC were determined and the CMC was determined by the intersection of the two straight lines. The CMC was determined to be 0.08 ± 0.01 g/L at 20 °C in water.

Reference 2

Endpoint:

water solubility

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Justification for type of information:

JUSTIFICATION FOR DATA WAIVING
In accordance with REACH Annex XI, section 2 it was technically not feasible to perform the standard test for water solubility according to OECD 105 as the substance is a surfactant. In accordance with the ECHA guidance on Guidance on Information Requirements and Chemical Safety Assessment Chapter R.7a: Endpoint specific guidance pg 79 a working approach for surfactants might be to take the critical micelle concentration in water (CMC) as a solubility limit, in order to avoid the artefact of unrealistically low Kow values. Thus, the critical micelle concentration in water conducted alternatively.

Description of key information

The critical micelle concentration was determined to be 0.08 ± 0.001 g/L at 20 °C.

Key value for chemical safety assessment

Water solubility:

0.08 g/L

at the temperature of:

20 °C

Additional information

In accordance with REACH Annex XI, section 2 it was technically not feasible to perform the standard test for water solubility according to OECD 105 as the substance is a surfactant. In accordance with the ECHA guidance on Guidance on Information Requirements and Chemical Safety Assessment Chapter R.7a: Endpoint specific guidance pg 79 a working approach for surfactants might be to take the critical micelle concentration in water (CMC) as a solubility limit, in order to avoid the artefact of unrealistically values. Thus, the critical micelle concentration in water conducted alternatively.

A study was conducted to determine critical micelle concentration (CMC) of the test item in water. The substance is a surfactant and thus the determination of the water solubility was technically not feasible. Upon reaching CMC, any further addition of test item will just increase the number of micelles. Below the CMC concentration the test item only individual surfactant molecules are present. Using the plate method to determine the surface tension, three individual experiments were performed to determine the surface tension as a function of the test item concentration. The functions of the two curves above and below the CMC were determined and the CMC was determined by the intersection of the two straight lines. The CMC was determined to be 0.08 ± 0.01 g/L at 20 °C in water.