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Surface tension

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Reference
Endpoint:
surface tension
Type of information:
experimental study
Adequacy of study:
key study
Study period:
11 May 2018 to 06 November 2018
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
equivalent or similar to
Guideline:
EU Method A.5 (Surface Tension)
Deviations:
yes
Remarks:
Due to the complexity of the test item, it was considered not completely applicable to follow the EC A.5 method with regard to sample preparation. Therefore, surface tension at concentration of 90% critical micelle concentration (CMC) was measured.
GLP compliance:
yes (incl. certificate)
Type of method:
ring method
Specific details on test material used for the study:
Batch number: TG 3774
Purity: 97% (by HPLC)
Expiry date: 01 July 2020
Key result
Surface tension:
38.8 mN/m
Temp.:
20 °C
Conc.:
139 mg/L

The mean reading for each sample solution was calculated from those values obtained that were considered to be on a plateau. The surface tension is given in mN/m.

The (critical micelle concentration) CMC was calculated from the anti-log of the interception of the two lines of best fit, plotted on the surface tension versus log concentration plot: Line 1 (y = -15.0x + 70.9) was generated from linear regression of 4 sample solution concentrations for which the surface tension was shown to be concentration dependent. Line 2 (y = -4.98x + 49.0) was generated from linear regression of 2 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, which was determined to be 154 mg/L.

The surface tension at a concentration of 90% of the CMC (139 mg/L) was calculated to be 38.8 mN/m using the equation for Line 1.

The sample solution at 302.3 mg/L was not used in generating the two lines: at this concentration the surface tension appeared to be transitioning to Line 2 at a shallower gradient than Line 1. The sample solutions at 1.008, 0.3023 and 0.1008 mg/L were not used in generating the two lines. At these concentrations the surface tension was only slightly affected and was approaching that of purified water.

The surface tension of the test item, based on the requirements of EC A.5 and OECD 115 guidelines, was calculated from 90% of the CMC.

Results

Concentration (mg/L)

Reading (mN/m)

Temperature (°C)

2.016E3

32.5

20.2

 

32.5

20.2

 

32.5

20.2

1.008E3

34.0

20.2

 

34.0

20.2

 

34.0

20.2

302.3

37.5

20.2

 

37.5

20.2

 

37.5

20.2

100.8

40.0

20.2

 

40.0

20.2

 

40.0

20.2

30.23

50.0

20.2

 

50.0

20.2

 

50.0

20.2

10.08

55.5

20.2

 

55.5

20.2

 

56.0

20.2

3.023

63.5

20.2

 

63.5

20.2

 

63.0

20.2

1.008

69.5

20.2

 

69.5

20.2

 

69.5

20.2

0.3023

72.0

20.2

 

72.0

20.2

 

72.0

20.2

0.1008

72.0

20.2

 

72.5

20.2

 

72.5

20.2

 

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

Concentration (mg/L)

Log10 Concentration

Mean Surface Tension (mN/m)

Solution pH

2.016E3

3.304

32.5

10.6

1.008E3

3.003

34.0

10.2

302.3

2.480

37.5

9.6

100.8

2.003

40.0

8.6

30.23

1.480

50.0

7.3

10.08

1.003

55.7

6.7

3.023

0.480

63.3

6.4

1.008

0.003

69.5

6.1

0.3023

-0.520

72.0

6.0

0.1008

-0.997

72.3

6.0

Conclusions:
The aqueous critical micelle concentration of the test item was determined to be 154 mg/L at 20.0 ± 0.5 °C via the ring method, measured in a GLP study run using a procedure based on EC A.5 and OECD 1995. The surface tension at an aqueous concentration of 90% of the CMC (139 mg/L) was calculated to be 38.8 mN/m at 20.0 ± 0.5 °C. The test item was considered to be surface-active.
Executive summary:

The aqueous critical micelle concentration of the test item was determined to be 154 mg/L at 20.0 ± 0.5 °C via the ring method, measured in a GLP study run using a procedure based on EC A.5 and OECD 1995. The surface tension at an aqueous concentration of 90% of the CMC (139 mg/L) was calculated to be 38.8 mN/m at 20.0 ± 0.5 °C. The test item was considered to be surface-active.

Description of key information

The aqueous critical micelle concentration of the test item was determined to be 154 mg/L at 20.0 ± 0.5 °C via the ring method, measured in a GLP study run using a procedure based on EC A.5 and OECD 1995. The surface tension at an aqueous concentration of 90% of the CMC (139 mg/L) was calculated to be 38.8 mN/m at 20.0 ± 0.5 °C. The test item was considered to be surface active.

Key value for chemical safety assessment

Surface tension:
38.8
in mN/m at 20°C and concentration in mg/L:
139

Additional information