Reaction products of 1H-Imidazole-1-ethanol, 4,5-dihydro-, 2-(C7-C17 odd-numbered, C17-unsatd. alkyl) derivs. and sodium hydroxide and chloroacetic acid

Partition coefficient

Description of key information

Because of its extreme solubility in water, its lower solubility in octanol and because it is technically not possible to measure the logKow, it is considered justified to take a pragmatic approach for this substance and to derive a log Kow of -1 to use for the CSA, by concluding that it is assumed that the water solubility of the substance is 10 times higher than its n-octanol solubility. This log Kow of -1 is supported by a calculated log Kow  of –0.64 to -4.19 for a group of constituents obtained with KOWWIN.

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, 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. It was considered justified to study the Kow by 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 it was shown that:

-The water solubility of the substance is extremely high (>1000 g solids /L)

- The n-octanol solubility of the substance at 20°C is < 82 mg solids/L based on visual estimation (while surfactant constituents of the substance were found dissolved).

-The different constituents of the substance dissolve at different concentrations in n-octanol.

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. Nevertheless the solubility in water was measured to be more than 1000000 mg/L and the solubility in octanol less than 82 mg/l. Owing to the relatively large hydrophilic part (amidoamine glycinate function), and the fact that the surfactant fraction is always under ionized form and in particular as a sodium salt form as manufactured, the solubility of the surfactant fraction in water was found to be very high and clearly above the solubility in n-octanol in the screening estimate.

Because of its extreme solubility in water, its lower solubility in octanol and because it is technically not possible to measure the logKow, it is considered justified to take a pragmatic approach for this substance and to derive a log Kow of -1 for the CSA, by concluding that it is pragmatically assumed that the water solubility of the substance is 10 times higher than its n-octanol solubility.

For difficult substances it is recommended to compare measured values with a calculated value. Therefore the log Kow for various 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. The lower alkyl derivatives are also showing calculated logKow below -2.6. This group of potential amidoamine glycinates are expected to constitute around 80% of the surfactant fraction in average (see section 1 of the dossier). Only some of the potential structures among the longer alkyl chains (C16 and C18) derivatives had a calculated LogKow above 0 (0.35 to 1.33) while the longer alkyl chains with dicarboxylate forms had calculated log Kow ranging from -0.75 to -2.2. 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 based on the measurements in water and in n-octanol. 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.

Based on the complex and not totally defined composition of the substance which contains variable chain lengths with a higher proportion of C12 and C14 derivatives and a high concentration of NaCl and taking into account the tensio-active properties of the surfactant fraction and the fact that classical methods cannot be used, it is reasonable to assume a log Kow value of -1. This log Kow of -1 is justified on the basis of the experimental determined solubilities in water and in octanol, and on the basis of the calculated log Kow of –0.64 to -4.19 for the main part of the surfactant fraction obtained with KOWWIN.