Rhamnolipids: fermentation products of glucose with Pseudomonas putida, Pseudomonadaceae

Water solubility

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

December 2022

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Remarks:

For the cmc measurement no guideline could be identified. Yet for the actual study, measurement is documented with raw data (including diagrams), identification of equipment, description of measurement process, summary, identification of test substance. As a consequence the study and its documentation is sufficiently trustworthy to be used for risk assessment.

Qualifier:

equivalent or similar to guideline

Guideline:

other: scientifically accepted guidance

Principles of method if other than guideline:

The critical micelle concentration (cmc) was examined using tensiometry which represents an accepted scientific method. The surface tension of a surfactant solution does no longer change at the onset of cmc formation.

GLP compliance:

no

Type of method:

other: The cmc was determined using a tensiometer by plotting surface tension (mN/m) against concentration of the test item in solution (%). The cmc is regarded the relevant parameter for water solubility of surfactants.

Water solubility:

ca. 200 other: ppm

Conc. based on:

act. ingr.

Remarks on result:

other: critical micellar concentration. the surface tensions of RL indeed depends upon the pH value of the solution. Since the original pH of about 6 increases by dilution with water to pH 7-8, the CMC has been determined at pH values of 5.5, 7 and 8.

Details on results:

the value for the CMC of Rhamnolipids can be estimated to be approx. 0.02 wt-% or 200 ppm (based on active content).

Conclusions:

Although according to the ISO Standard 4311-1979 no value can be given, the CMC of RL can be assumed to be approx. 200 ppm.
It should be acknowledged that this CMC value is the maximum water solubility as surfactant monomers, which is the value often used to calculate log Kow. This value should not be confused with the “macroscopic” water solubility as surfactant aggregates (micelles), which is definitely >50 wt-%, since RL products are typically sold as 50 wt-% aqueous solutions.

Reference 2

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

2017-01-18 - 1017-02-14

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

The test was done at a lab with good reputation according to OECD guideline 105 with enhanced preliminary testing.The result obtained is valid for the statement of high solubility in water. According to Reach Annex XI, 1.1 further testing on water solubility is scientifically unjustified.

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Version / remarks:

1995

Qualifier:

according to guideline

Guideline:

EU Method A.6 (Water Solubility)

Version / remarks:

Council Regulation (EC) No. 260/2014

Principles of method if other than guideline:

Enhanced Preliminary Test with two replicates was done.

GLP compliance:

no

Type of method:

flask method

Key result

Water solubility:

>= 353 g/L

Conc. based on:

test mat.

Loading of aqueous phase:

1.1 g/L

Incubation duration:

ca. 13 h

Temp.:

22 °C

Remarks on result:

other: loading of the aqueous phase: 1.1489 g resp. 1.0820 g / 2 mL water

Remarks:

The densitiy of the replicates at 33% w/w was determined to be 1.06 g/mL for both replicates

Water solubility:

33 other: %w/w

Conc. based on:

test mat.

Incubation duration:

ca. 13 h

Temp.:

22 °C

Remarks on result:

other: pH was not determined in this preliminary range finding test

see attachment

Conclusions:

The test material had a solubiity of ≥ 353 g/L at ca. 22 °C.

Executive summary:

The water solubility of the test material was tested according to OECD guideline 105, shake flask method, in a non-GLP test. Within the enhanced preliminary test remaining undissolved matter was checked visually and in addition checked with Tyndall effect on the absence of colloidal dispersed material. The test resulted in a solubility of ≥ 353 g/L at ca. 22°C.

Description of key information

The test resulted in a solubility test according to OECD 105 of ≥ 353 g/L at ca. 22°C. The value for the CMC of Rhamnolipids can be estimated to be approx. 0.02 wt-% or 200 ppm (based on active content).

Key value for chemical safety assessment

Water solubility:

353 g/L