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Partition coefficient

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Reference
Endpoint:
partition coefficient
Type of information:
(Q)SAR
Adequacy of study:
supporting study
Study period:
N/A
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
accepted calculation method
Justification for type of information:
QSAR prediction
Qualifier:
according to
Guideline:
other: ECHA Guidance on information requirements and chemical safety assessment, Chapter R6, QSAR and grouping of chemicals
Deviations:
no
Principles of method if other than guideline:
Calculation with the KOWWIN Program (v1.67) in the US EPA 2009 Estimation Programs Interface (EPI) SuiteTM for Microsoft® Windows, version 4.00
GLP compliance:
no
Type of method:
other: Model KOWWIN v1.67
Partition coefficient type:
octanol-water
Analytical method:
other: Not applicable
Key result
Type:
log Pow
Partition coefficient:
-4.19 - -0.64
Remarks on result:
other: Since the substance is an UVCB with a composition which is not totally defined, the log Kow calculations were done for the known structures of the surfactant fraction.
Details on results:
Since the substance is an UVCB with a composition which is not totally defined, the log Kow calculations were done for the known structures of the surfactant fraction.

No warning from the program outcome is reported, so the proposed smiles are inside the program's prediction domain. Moreover it was checked that all the fragments used to calculate the log Kow of the alkyl amphoacetates structures are represented in the model.

Constituent

SMILES

Log Kow

C12 alkyl amphoacetate Form A Monoacetate

CCCCCCCCCCCC(=O)NCCN(CCO)CC(=O)O[Na]

-1.62

C12 alkyl amphoacetate Form B Monoacetate

CCCCCCCCCCCC(=O)N(CCO)CCNCC(=O)O[Na]

-1.62

C12 alkyl amphoacetate Form A Diacetate

CCCCCCCCCCCC(=O)NCCN(CCOCC(=O)O[Na])CC(=O)O[Na]

-3.7

C12 alkyl amphoacetate Form B Diacetate

CCCCCCCCCCCC(=O)N(CCO)CCN(CC(=O)O[Na])CC(=O)O[Na]

-4.19

C14 alkyl amphoacetate Form A Monoacetate

CCCCCCCCCCCCCC(=O)NCCN(CCO)CC(=O)O(Na)

-0.64

C14 alkyl amphoacetate Form B Monoacetate

CCCCCCCCCCCCCC(=O)N(CCO)CCNCC(=O)O(Na)

-0.64

C14 alkyl amphoacetate Form A Diacetate

CCCCCCCCCCCCCC(=O)NCCN(CCOCC(=O)O[Na])CC(=O)O(Na)

-2.72

C14 alkyl amphoacetate Form B Diacetate

CCCCCCCCCCCCCC(=O)N(CCO)CCN(CC(=O)O[Na])CC(=O)O(Na)

-3.21

 

The potential structures derived from the major alkyl chains C12 and C14 have individual calculated log Kow ranging from – 0.64 to -4.19 as sodium salts. 

Because of the complexity of the substance and since the exact structures and proportions of each tension-active constituent cannot be determined, it is not possible to refine more the calculated log Kow based on QSAR’s.

Conclusions:
Applying the KOWWIN Program (v1.67) in the US EPA 2009 Estimation Programs Interface (EPI) SuiteTM on the main structures of the surfactant fraction of the substance, the calculated log Kow is estimated to be between -0.64 and -4.19. Because of the complexity of the substance and since the exact structures and proportions of each surfactants constituents cannot be determined, it is not possible to refine more the calculated log Kow based on QSAR’s.
Executive summary:

For difficult substances it is recommended to compare measured values with a calculated value. Therefore the log Kow for potential constituents of the surfactant fraction was also calculated using the KOWWIN Program (v1.67) in the US EPA 2009 Estimation Programs Interface (EPI) SuiteTM for Microsoft® Windows, version 4.00. For this estimation the Nacl constituent was not taken into account.

The potential structures derived from the major alkyl chains C12 and C14 had all individual calculated log Kow ranging from – 0.64 to - 4.19 as sodium salts.

It is acknowledged that the Kow calculation model is not fully applicable to surfactants, as they tend to partition at the interface between both media. Nevertheless these QSAR’s values show consistency with the pragmatically assumed log Kow (-1). Because of the complexity of the substance and since the exact structures and proportions of each surfactants constituents cannot be determined, it is not possible to refine the calculated log Kow based on QSAR’s.

Description of key information

Based on the complex and not totally defined composition of the substance and taking into account the tensio-active properties of the surfactant fraction and the fact that classical methods cannot be used, it is considered reasonable to assume a log Kow value of -1. It is pragmatically assumed that the water solubility of the substance is 10 times higher than its n-octanol solubility, as the surfactant fraction of the substance is always under ionized form and in particular as a sodium salt form as manufactured. This log Kow of -1 is supported by a calculated log Kow of –0.64 to -4.19 for the main part of the surfactant fraction.

Key value for chemical safety assessment

Log Kow (Log Pow):
-1
at the temperature of:
20 °C

Additional information

As the substance is an UVCB substance, containing numerous surface active constituents and NaCl, it is expected that NaCl and the different surfactant constituents will behave differently in water and in octanol. So the standard test methods are not appropriate to measure the log Kow. The only suitable method was considered to be the estimation method, as all other methods were assessed to be not adequate; review of available methods:

HPLC method:

-Not suitable for surfactants and for switterionic substances

Flask method:

-Not suitable for surface active substances

-Not suitable for substances with many constituents

-Quantitative determination of the substance concentration in water and octanol is not possible

Calculation method:

-Not suitable as calculations are not possible for all constituents

-Not suitable for substances with many constituents, leading to a broad range with limited use

-Not suitable for salts

-Unreliable as it was shown that different calculation methods gave different results

Slow stirring method:

-Not suitable for substances with many constituents

-Quantitative determination of the substance concentration in water and octanol is not possible

Estimation method:

The estimation method is another alternative method cited in the guidance: Guidance on information requirements and chemical safety assessment, Chapter R.7a: Endpoint specific guidance. The estimation method is based on a separate measurement of the solubility in water and in octanol followed by the ratio of these measurements to estimate the Kow: Kow = [n-octanol] / [water]. On the basis of the conducted solubility tests in water and in octanol with the substance and with analogues it was shown that:

- The water solubility of the substance is extremely high. Visually it was determined that a solution of 206.4 g/L in water results in a clear solution without undissolved material.

- The n-octanol solubility of the surfactant part of the substance (determined analytically, only for the analogue amphoacetates C12) is also extremely high.

- Visual it was determined that a solution of 1.1 g/L in n-octanol results in a solution with undissolved material. The in n-octanol undissolved particles observed in the study most probably derive from sodium chloride.

 

Also with the estimation method it is concluded that it is technically not possible to determine a reliable estimate of the log Kow for this complex and variable substance.