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Physical & Chemical properties

Water solubility

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Reference
Endpoint:
water solubility
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Qualifier:
no guideline followed
Principles of method if other than guideline:
The test item is visually unlimited soluble in water. Therefore, the OECD Guideline 105 (column elution method and flask method) is not applicable. For surfactants the determination of the critical micelle concentration (CMC) could indicate the water solubility as molecules. The CMS can be determined via surface tension measurements on a series of different surfactant concentrations. CMC measurements were carried out using the autodilution method (reverse CMC). A stock solution of 1000 mg/L C8-18 AAPB was subject of dilution.
GLP compliance:
not specified
Type of method:
other: determination of water solubility via CMC measurements
Key result
Water solubility:
<= 400 mg/L
Temp.:
20 °C
Remarks on result:
other: pH
Remarks:
no data on pH

The test item is visually unlimited soluble in water. Therefore, the OECD Guideline 105 (column elution method and flask method) is not applicable. Therefore it was tried to determine the water solubility via the measurement of the critical micelle concentration (CMC). CMC measurements were carried out using the autodilution method (reverse CMC) and an average surface tension vs. concentration curve was constructed. A well-defined CMC was not observed due to presence of different fatty acid derivates in the test substance each having a different CMC. The CMC range at 20°C of C8 -18 AAPB was determined to be ca. 400 -900 mg/L. Therefore the water solubility of C8 -18 AAPB molecules is <=400 mg/L.

Conclusions:
The water solubility of C8-18 AAPB based on surface tension measurements is <=400 mg/L (CMC range: 400-900 mg/L).
Executive summary:

The measurement of the water solubility according to OECD Guideline 105 is not feasible due to the visual unlimited solubility in water. Therefore, the attempt was undertaken to determine the water solubility via the CMC/surface tension. A well-defined CMC was not observed which is caused by the presence of different fatty acid derivates in the test substance each having a different CMC. The CMC range at 20°C of C8 -18 AAPB was determined to be ca. 400 -900 mg/L. Therefore the water solubility of C8 -18 AAPB molecules is <=400 mg/L.

Description of key information

C8-18 AAPB, C12 AAPB : visually unlimited soluble in water (formation of micelles)
C8-18 AAPB molecules: <=400 mg/L at 20°C (based on surface tension/CMC measurements); CMC formation range: 400-900 mg/L
C12 AAPB molecules is <=250 mg/L at 20°C (based on surface tension/CMC measurements); CMC: ca. 250 mg/L

Key value for chemical safety assessment

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

Additional information

(formation of micelles. The water solubilities of C8-18 AAPB and C12 AAPB molecules based on surface tension measurements are <=400 mg/L at 20°C. All AAPBs are similar in structure, contain all the same zwitterionic structure. They differ, however, by their carbon chain length distribution and the degree of unsaturation (<=20%) in the fatty acid moiety. The content of minor constituents in all products are comparable and differ to an irrelevant amount. Based on the available data, it can be assumed that chain length distribution and degree of unsaturation of the fatty acid chain have a minor impact on this endpoint.