Registration Dossier
Registration Dossier
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EC number: 943-175-7 | CAS number: -
Partition coefficient
Administrative data
Link to relevant study record(s)
- Endpoint:
- partition coefficient
- Type of information:
- calculation (if not (Q)SAR)
- Adequacy of study:
- weight of evidence
- Study period:
- 02.02.2023
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- accepted calculation method
- Justification for type of information:
- Justification for using the calculation method
According to Echa guidance R7a (2017), p78:
Guidance on regulatory compliant Kow determination for surfactants:
In many cases a calculated Kow value based on the octanol and water solubilities will be the first choice for surfactants. It is also useful to compare a calculated with a measured value. For the calculation approaches, one needs to consider the pH of the system (which determines the ionisation of the surfactant – see Section R.7.1.17). None of the experimental methods is very well suited for determining the Kow of surface active substances. The shake flask method is the least suitable experimental method for surfactants. HPLC methodology may fail due to secondary interactions, and is sensitive to fluctuations of ionic strength. The slow stirring method in theory is the best, but still not demonstrated to be perfect. If using slow stirring, one needs to demonstrate a consistent result when starting with the surfactant in either phase, not just in the octanol. A working approach for surfactants might be the comparison of measured solubilities in octanol and water. However, it would then be prudent to take the critical micelle concentration in water (cmc) as a solubility limit, in order to avoid the artefact of unrealistically low Kow values.
The calculation of logKow from solubilities in water (determined via cmc) and octanol in many cases is the first choice for its derivation.
- Reason / purpose for cross-reference:
- reference to other study
- Reason / purpose for cross-reference:
- reference to other study
- Qualifier:
- no guideline followed
- Principles of method if other than guideline:
- Calculation from critical micelle concentration and solubility in octanol as described in ECHA guidance R7a (2017).
- Type of method:
- estimation method (solubility ratio)
- Partition coefficient type:
- octanol-water
- Analytical method:
- other: calculation from critical micelle concentration and solubility in octanol
- Type:
- log Pow
- Partition coefficient:
- 3
- Remarks on result:
- not measured/tested
- Remarks:
- calculated
- Details on results:
- For details on the calculation, please see section "any other information on results incl. tables".
- Conclusions:
- The estimated logKow calculated from cmc and solubility in octanol is estimated calculated logKow = 3.
- Executive summary:
In this calculation, the logKow of Rhamnolipids: fermentation products of glucose with Pseudomonas bacteria was determined. The calculation of logKow from solubilities in water (determined via cmc) and octanol in many cases is the first choice for its derivation. As Rhamnolipid is a surfactant (surface tension < 40 mN/m) with acid/base active functional groups, the results from logKow determination via the HPLC method are questionable. Additional interactions between Rhamnolipid charged groups and polar groups of the HPLC-column are expected that are not adequately considered by the reference compounds used at the pH of the mobile phase. This makes the result from HPLC logKow determination doubtful. Furthermore, ECHA guidance R7a (2017), p78, recommends to take the critical micelle concentration in water (cmc) as a solubility limit, in order to avoid the artefact of unrealistically low Kow values. The calculations lead to the following values:
Estimated calculated logKow = 3
Reference
Calculation
Water solubility from cmc determination:
0.02 % = 0.2 g/L
Octanol solubility:
200 g/L
Kow = Coctanol / Cwater
Kow = Coctanol / min. Cwater = 200 g/L / 0,2 g/L = 1000; logKow = 3
estimated calculated logKow = 3
Description of key information
The estimated logKow calculated from cmc and solubility in octanol is estimated calculated logKow = 3.
Key value for chemical safety assessment
- Log Kow (Log Pow):
- 3
- at the temperature of:
- 22 °C
Additional information
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