Oxoaluminium, C16-C18-alkyl esters

Endpoint summary

Description of key information

Appearance/physical state/colour

The substance as a 50% w.w. concentration in pharmaceutical white oil is a pale yellow viscous liquid at ambient temperature.The data are taken from substance identification information in a GLP-compliant, guideline study available as an unpublished report (Harlan 2013).

Melting point/freezing point

The pour point of the substanceas a 50% w.w. concentration in pharmaceutical white oil is 21 ± 3°C. The pour point was determined in a GLP-compliant thermal analysis test, using differential scanning calorimetry, following OECD guideline 102 (Harlan 2013).

Boiling point

No experimental determination of the boiling temperature was possible for the substanceas detailed in Method A2 Boiling Temperature of Commission Regulation (EC) No 440/2008 of 30 May 2008, and Method 103 of the OECD Guidelines for Testing of Chemicals, 27 July 1995, becausedue to the presence of the pharmaceutical white oil, it was not possible to identify thermal events specific to the substancecontent of the test item.

Density

The relative density of the substanceas a 50% w.w. concentration in pharmaceutical white oil is 0.933 at 20 ± 0.5°C. The density of the test item was determined in a GLP-compliant air comparison pycnometer test following OECD guideline 109 (Harlan 2013).

Granulometry

The particle size distribution test has been waived because the substance is manufactured or used in a non-solid or granular form. The substance only exists in the presence of an inert carrier. As the substance is only manufactured in situ in a generic inert carrier, typically base oil, and the base oil retards the surface oxidation of the isolated substance, the hazard testing was conducted on the substance in situ in a carrier. All endpoints, where possible were determined using a 50% w.w. concentration in pharmaceutical white oil.

Vapour pressure

The vapour pressure of the substanceas a 50% w.w. concentration in pharmaceutical white oil has been determined to be 0.00015 Pa at 25°C. The vapour pressure of the test item was determined in a GLP-compliant study (Harlan 2013) following OECD guideline 104.

Water solubility

The water solubility of the substanceas a 50% w.w. concentration in pharmaceutical white oilhasbeen determined to be less than 0.00015 g/L of solution at 20.0 ± 0.5°C, based on test substance. The water solubility of test item was determined in a GLP-compliant, analysis study (Harlan 2013) following OECD guideline 105.

Partition Coefficient

No determination of the partition coefficient was possible by the shake-flask method due to the insolubility of the test itemin both n-octanol and water. Further to this, determination of the partition coefficient by the HPLC estimation method was also not possibledue to the insolubility of the test itemin suitable reverse phase HPLC solvents.

The partition coefficient was estimated by QSAR but the result is considered not to be relevant to the substance itself. As the substanceis anionisable salt, the partition coefficient can vary greatly depending on pH and the pKa of the substance. In order to compare partition coefficient values of different, ionizable compounds on a relative basis, partition coefficient values are sometimes reported as "corrected for ionization", indicating that the value represents the partition coefficient at a pH where a compound exists primarily in the non-ionized form. However, KOWWIN (KOWWIN v1.67 in EPISuite v4.00, US EPA 2009) considers the substanceto be “ion pairs” and as such only provides estimates for the ionised fatty acids rather than the salt. The partition coefficient value for the salt itself therefore could not be determined.

The substance is only manufactured in situ in a generic inert carrier, typically base oil. High temperature stability indicates that the grease thickener structure is robust and resistant to diffusion out of the carrier. Dissolution of the grease thickener from grease into water is very unlikely as the thickener is poorly water soluble and the thickener is embedded in the hydrophobic grease matrix and thus less likely to leach out. Thus the partition coefficient of the substance is not expected to be relevant.

Surface tension

The surface tension of duplicate 90% saturated aqueous solutions of the substanceas a 50% w.w. concentration in pharmaceutical white oilhas been determined to be 72.5 mN/m at 20.0 ± 0.5°C. Since the substance showed a surface tension greater than 60 mN/m it was considered not to be surface active. The surface tension of the test material was conducted in a GLP-compliant ring balance test following OECD guideline 115 (Harlan 2013).

Flash Point

The substance as a 50% w.w. concentration in pharmaceutical white oil was determined to have a flash point of 159°C (not corrected to standard atmospheric pressure).The flash point of the test item was determined in a GLP-compliant study following EC 440/2008 A9 method (Harlan 2013).As the flash point is > 60ºC the substance does not meet the criteria for a flammable liquid.

Auto-flammability

The substance as a 50% w.w. concentration in pharmaceutical white oil was determined to have an auto-ignition temperature of 374°C, which is above its melting point. The relative self-ignition temperature of the test item was determined in a GLP-compliant study following EC 440/2008 A15 method (Harlan 2013).

Flammability

As the substance is only manufactured in situ in a generic inert carrier, typically base oil, and the base oil retards the surface oxidation of the isolated substance, the hazard testing was conducted on the substance in situ in a carrier. All endpoints, where possible, were determined using a 50% w.w. concentration in pharmaceutical white oil.

As the substance as a 50% w.w. concentration in pharmaceutical white oil is a liquid, its flammability is determined on the basis of its flash point and boiling point. Experience in manufacture and handling shows that the substance in a grease base does not ignite spontaneously on coming into contact with air or water at normal temperatures and therefore does not meet the criteria for classification as a pyrophoric substance or a substance which in contact with water emits flammable gases.

Dissociation constant

No data are available on the dissociation constants for the substanceso the dissociation constants have been read across from sodium palmitate (Kanicky et al 2000) and potassium stearate (Kanicky and Shah 2002).Kanicky et al. (2000) titrated sodium palmitate with sodium hydroxide and calculated the mean pKa from the pH at half the neutralisation volume for each of the five replicates. Kanicky and Shah (2002) titrated potassium stearate with hydrochloric acid and calculated the mean pKa from the pH at half the neutralisation volume for each of the five replicates. The studies are non-GLP, non-guideline experiments, available in peer-reviewed published journal articles. The experiments follow sound scientific principles and are considered adequate for assessment.

At neutral pH, and within the limits of solubility, the substanceisexpected to dissociate into aluminium species, mainly aluminium hydroxide and fatty acid anions. The fatty acid anions would then be expected to achieve equilibrium with respect to the H+ ions in the water (depending on the pKa of the fatty acids) and at neutral pH there would be ionised acids, unionised acids, and aluminium hydroxide species. Asthe dissociation constant of the substanceisexpected to be determined by the equilibrium of the fatty acidswith the hydrogen ions in the water,read across between the same fatty acids is considered to be justified.The measured dissociation constant for sodium palmitate of 8.8 (Kanicky et al. 2000) and for potassium stearate of 10.15 (Kanicky and Shah 2002) are both relatively high and thus any dissociated fatty acid would be expected to be unionised (protonated) at environmental pH.

Viscosity

The kinematic viscosity of the substanceas a 50% w.w. concentration in pharmaceutical white oil is 174.3 mm2/s at 100°C. The kinematic viscosity was determined in a non-GLP-compliant guideline study (MOL-LUB 2013).

Other physico-chemical endpoints

As the substanceas 50% w.w. concentration in pharmaceutical white oil is aviscous liquid, a flammability study is not required. Based on the structure of the substance, the explosiveness and oxidising properties studies have not been conducted as there are no structural alerts that would indicate explosive or oxidising properties. The stability in organic solvents and identity of relevant degradation products study has not been conducted as it is not considered to be a critical endpoint. As the substance is manufactured and used in situ in an inert carrier, typically base oil, and marketed or used in non-solid or granular forms, the particle size distribution test has been waived.

Classification and labelling

The substance is not classified for physico-chemical hazards. Based on the structure of the substance, it does not meet the criteria for oxidising or explosive properties and based on experimental data, the substance does not meet the criteria for a flammable liquid. Experience in manufacture and handling shows that the substance is not self-heating.

Additional information

As the substance is only manufactured in situ in a generic inert carrier, typically base oil, and the base oil retards the surface oxidation of the isolated substance, the hazard testing was conducted on the substance in situ in a carrier. All endpoints, where possible, were determined using a 50% w.w. concentration in pharmaceutical white oil. The presence of the pharmaceutical white oil will very likely have a strong influence on the properties of the substance. However, since the substance is always manufactured and used in the presence of an inert carrier, testing on the substance in a pharmaceutical white oil is considered justified.