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Water solubility

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Endpoint:
water solubility
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Study period:
From December 06, 2006 to January 19, 2007
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Justification for type of information:
Refer to the Quaternary ammonium salts (QAS) category or section 13 of IUCLID for details on the category justification.
Reason / purpose for cross-reference:
reference to same study
Qualifier:
according to guideline
Guideline:
other: OECD Guideline 115 (Surface Tension of Aqueous Solutions)
Version / remarks:
27 July 1995
Deviations:
no
Qualifier:
according to guideline
Guideline:
other: EU Method A.5 (Surface Tension)
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:
yes (incl. QA statement)
Type of method:
other: by determining the surface tension of a range of aqueous sample solutions of differing concentration
Key result
Water solubility:
ca. 500 mg/L
Conc. based on:
test mat.
Temp.:
20 °C
Remarks on result:
other: CMC determined for C14 chain length
Water solubility:
1 000 mg/L
Conc. based on:
test mat.
Temp.:
20 °C
Remarks on result:
other: CMC determined for C12 chain length
Details on results:
Please see below table.

Results

Table1: Surface tension of 1 g/L aqueous solution of test substance

Measurement #

Measurement time (s)*

Surface tension [mN/m]

Temperature [deg C]

1

960.3

28.35

19.8

2

989.6

28.32

19.8

3

1018.4

28.3

19.7

4

1047.1

28.258

19.8

5

1075.3

28.28

19.8

6

1103.6

28.26

19.8

7

1132.9

28.23

19.8

8

1161.3

28.24

19.8

9

1189.3

28.21

19.8

10

1218.3

28.2

19.8

MV

-

28.27

19.8

SD

-

0.05

0.03

Table 2: Surface tension of test substance at different concentrations

Concentration (g/L)

Reading (mN/m)

Temperature (°C)

0.02

46.5

20.1

0.04

45.43

20.2

0.10

38.46

20.0

0.15

35.98

19.7

0.20

34.88

19.7

0.25

34.28

20.0

0.30

32.90

20.2

0.40

30.82

19.8

0.50

28.90

19.9

0.70

29.95

19.9

1

28.27

19.8

2.50

33.03

19.8

5

34.91

19.8

The plot of log10[concentration (g/L)] versus surface tension (mN/m) can be found under Illustration section of the IUCLID' :

The CMC of an aqueous solution of the test substance was interpolated to be 0.5 g/L.

Discussion

The critical micelle concentration (CMC) is an important characteristic of a surfactant. At low concentrations of surfactant, the surface tension of water is only slightly affected. 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:
Under the study conditions, the the CMC as water solubility of the read across substance was determined to be 500-1000 mg/L at 20.0 ± 0.5°C.
Executive summary:

A study was conducted to determined the water solubility of the read across substance, C12 -16 ADBAC (94.4% active) based on critical micelle concentration (CMC), according to OECD Guideline 115 and EU Method A.5, in compliance with GLP. The CMC were determined to be 0.50 g/L for C14-chain length and 1.0 g/L for C12 -chain length. Due to the surface activity of the read across substance, the CMC value was considered as a water solubility equivalent in accordance with the ECHA R.7a Guidance. Under the study conditions, the CMC of the read across substance was determined to be 500 -1000 mg/L at 20.0 ± 0.5°C (Schulze, 2007). Based on the results of the read across, a similar water solubility is expected for the test substance.

Endpoint:
water solubility
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
supporting study
Study period:
From September 21, 2006 to March 19, 2007
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
KL2 due to RA
Justification for type of information:
Refer to the Quaternary ammonium salts (QAS) category or section 13 of IUCLID for details on the category justification.
Qualifier:
according to guideline
Guideline:
OECD Guideline 105 (Water Solubility)
Deviations:
no
GLP compliance:
yes
Type of method:
flask method
Key result
Water solubility:
ca. 455 000 mg/L
Conc. based on:
test mat.
Loading of aqueous phase:
2 other: g
Incubation duration:
ca. 72 h
Remarks on result:
other: in bi-distilled water
Remarks:
at different temperatures and pH
Key result
Water solubility:
ca. 444 000 mg/L
Conc. based on:
test mat.
Loading of aqueous phase:
2 other: g
Incubation duration:
ca. 72 h
Remarks on result:
other: in buffer solutions
Remarks:
at different temperatures and pH
Details on results:
Stable: yes
Temperature effects: no

Results:
Bi-distilled water: 455000 mg/L (pH around 5.0)
Buffer solution pH 4: 444000 mg/L (pH: 3.81-3.98)
Buffer solution pH 7: 444000 mg/L (pH: 6.70-6.80)
Buffer solution pH 9: 444000 mg/L (pH: 8.11-8.30)

Conclusions:
Under the study conditions, the water solubility of the read across substance was determined to be 455000 mg/L in bi-distilled water and 444000 mg/L in buffer solutions and was independent of the temperature and pH.
Executive summary:

A study was conducted to determine the water solubility of the read across substance, C12-16 ADBAC (purity: 94.4%) according to OECD Guideline 105, in compliance with GLP. In this experiment, the solubility of the read across substance was determined using a modified flask method at 10, 20 and 30°C with a preincubation at 35°C. 2.0 g of the read across substance was soluble in 4.5 mL of buffer solutions (pH 4, 7 and 9) and 4.4 mL of bi-distilled water, respectively. Under the study conditions, the water solubility of the read across substance was determined to be 455000 mg/L in bi-distilled water and 444000 mg/L in buffer solutions and was independent of the temperature and pH (Schulze, 2007).  Based on the results of the read across, a similar water solubility is expected for the test substance.

             

Description of key information

The water solubility was determined based on a study conducted with read across substance, C12 -16 ADBAC using the modified flask method according to OECD Guideline 105 as well as based on the critical micelle concentration (CMC) method according to OECD Guideline 115 (Schulze, 2007)  

Key value for chemical safety assessment

Water solubility:
810 mg/L
at the temperature of:
20 °C

Additional information

CMC (based on read across study): 810 mg/L at 19.7 °C determined in partition coefficient study and 500 -1000 mg/L determined in surface tension study at 20 °C; water solubility (based on read across study) = 455000 mg/L in bi-distilled water and 444000 mg/L in buffer solutions (independent of the temperature and pH)

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