Phosphoric acid C12-alkyl and C18-alkyl esters, potassium salts

Water solubility

Link to relevant study record(s)

Reference

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2017-12-15

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Deviations:

yes

Remarks:

According to the Guidance on information requirements and chemical safety assessment, chapter R.7a, pp 77 and 107, since the substance is a surfactant, it is prudent to take the critical micelle concentration (CMC) as a solubility limit.

Qualifier:

according to guideline

Guideline:

other: ISO-standard n° 304-1985

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. Several test item solutions in in suitable volumetric flasks are prepared to cover concentrations between approx. 0.001 and 1 g/L. Each flask is slowly stirred during 15 min and then the solution is staying during 10 min in the tensiometer, where the temperature is assumed to be 20 °C, which is the measuring temperature for the surface tension. The measurement is started and after 15 minutes the value is taken. The experiment is repeated 3 times and the average value of the CMC of the test item assumed to be the water solubility.

GLP compliance:

no

Type of method:

other: critical micelle concentration (CMC)

Water solubility:

0.055 g/L

Conc. based on:

test mat.

Loading of aqueous phase:

1 g/L

Incubation duration:

15 min

Temp.:

20 °C

pH:

8.94

Remarks on result:

other: Critical Micelle Concentration

3 curves of the surface tension as a function of the concentration of test item in water were derived. For each curve, equations of the 2 straight lines and the calculated value of the CMC are picked up and summarised.

 

Curve	Straight line 1	Straight line 2	CMC (g|L)	Average	Standard deviation
1	y = -9.189 ln(x) + 9.7741	y = 1.4136 ln(x) +42.074	0.048	0.055	0.0075
2	y = -8.787 ln(x) + 11.878	y = 0.8026 ln(x) +38.464	0.063
3	y = -9.247 ln(x) + 10.113	y = -1.711 ln(x) + 31.97	0.055

 

The pH of a solution with a concentration of 0.999 g/L test item at 20 °C was determined to be pH = 8.94.

 

The individual results are as follows:

 

 

Concentration (g/L)	0.0017352	0.0024036	0.006009	0.010494	0.02115	0.06988	0.5425	1.0020
Surface tension (mN.m)	71.0	58.4	61.6	54.0	42.0	38.2	41.7	41.7

 

 

Concentration (g/L)	0.001891	0.002591	0.005453	0.007625	0.010855	0.019867	0.07940	0.64618	0.965
Surface tension (mN.m)	71.4	56.5	66.7	46.5	54.1	37.5	33.3	36.5	41.0

 

 

Concentration (g/L)	0.001579	0.002499	0.0074023	0.010539	0.014604	0.019673	0.074514	0.43263	0.993
Surface tension (mN.m)	71.3	62.1	57.4	53.9	50.0	43.9	36.8	32.2	32.8

 

Conclusions:

The water solubility expressed as critical micelle concentration was determined do to be 0.055 g/L at 20 °C.

Executive summary:

As the substance was determined to be a surfactant (refer to IUCLID section 4.10) the critical micelle concentration (CMC) was determined in accordance with the ECHA guidance on information requirements and chemical safety assessment, chapter R.7a, pp 77 and 107. It was concluded that this value is more reliable for the chemical safety assessment than the water solubility. Therefore, several test item solutions in in suitable volumetric flasks are prepared to cover concentrations between approx. 0.001 and 1 g/L. Each flask is slowly stirred during 15 min and then the solution is staying during 10 min in the tensiometer, where the temperature is assumed to be 20 °C, which is the measuring temperature for the surface tension. The measurement is started and after 15 minutes the value is taken. 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. The experiment is repeated 3 times and the average value of the CMC of the test item assumed to be the water solubility. The CMC was determined to be 0.055 g/L at 20 °C.

Description of key information

The water solubility of the substance was determined to be 55 mg/L.

Key value for chemical safety assessment

Water solubility:

55 mg/L

at the temperature of:

20 °C

Additional information

Key study (Infrapark Baselland, 2018)

As the substance was determined to be a surfactant (refer to IUCLID section 4.10) the critical micelle concentration (CMC) was determined in accordance with the ECHA guidance on information requirements and chemical safety assessment, chapter R.7a, pp 77 and 107. It was concluded that this value is more reliable for the chemical safety assessment than the water solubility. Therefore, several test item solutions in suitable volumetric flasks were prepared to cover concentrations between approx. 0.001 and 1 g/L. Each flask is slowly stirred during 15 min and then the solution is staying during 10 min in the tensiometer, where the temperature is assumed to be 20 °C, which is the measuring temperature for the surface tension. The measurement is started and after 15 minutes the value is taken. 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. The experiment is repeated 3 times and the average value of the CMC of the test item assumed to be the water solubility. The CMC was determined to be 0.055 g/L at 20 °C.

supporting study (Infrapark Baselland 2011)

As the source substance was determined to be a surfactant the critical micelle concentration (CMC) was determined in accordance with the ECHA guidance on information requirements and chemical safety assessment, chapter R.7a, pp 77 and 107. It was concluded that this value is more reliable for the chemical safety assessment than the water solubility. Therefore, several solutions in in suitable volumetric flasks are prepared to cover concentrations between approx. 0.001 and 1 g/L. Each flask is slowly stirred during 15 min and then the solution is staying during 10 min in the tensiometer, where the temperature is assumed to be 20 °C, which is the measuring temperature for the surface tension. The measurement is started and after 15 minutes the value is taken. 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. The experiment is repeated 3 times and the average value of the CMC of the source substance assumed to be the water solubility. The CMC was determined to be 53.3 +/- 3 mg/L at 20 °C.

Conclusion

The CMC for the target substance was determined to be 55 mg/L and for the source substance 53 mg/L respectively. In conclusion, it was shown that the water solubility expressed as critical micelle concentration is comparable for the target and the source substance.