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Environmental fate & pathways

Hydrolysis

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Description of key information

The test substance is stable at pH 4, 7 and 9 at 50 °C: it has a half-life period longer than one year at 25 °C at pH 4, 7 and 9.

Key value for chemical safety assessment

Half-life for hydrolysis:
1 yr
at the temperature of:
25 °C

Additional information

Hydrolysis is a common degradation route in the environment, namely the reaction of a substance with water with a net exchange of the X group with an OH at the reaction centre such that RX + H2O → ROH + HX. Hydrolysis is often dependent upon pH as the reaction is commonly driven by hydrogen or hydroxide ions. Hydrolysis kinetics are usually determined experimentally and should be used to consider the test type and whether parent or degradation product should be tested.

In the case of CAS 67786-25-8, it can be estimated that hydrolysis does not occur because there are not hydrolysable groups in any of the structures; this is also confirmed by calculation with HYDROWIN 2.0.

Hydrolysable organic groups are in fact those groups that can react with water like Esters, Anhydrides, Amides, Carbammates, Nitriles, Cyanates, Epoxides, Halomethanes, Alkylhalides, Urea and none of these groups are present within the substance or their impurities.

A reliable test on the Hydrolysis was conducted on an analogous substance of the Stilbene Fluorescent Whitening Agents category, group 3, CAS 16470-24-9, according to internationally accepted testing guidelines and performed according to GLP. The two substances (CAS 16470-24-9 and CAS 67786-25-8) are very similar and are constituted by the same functional groups, with the difference that CAS 16470-24-9 is the dihydroxyethylamino derivative, while CAS 67786-25-8 is the dihydroxyisopropylamino derivative. The difference has no impact on the hydrolysation potential, since both substances have no hydrolysable groups in the chemical structure. Quantity and chemical identity of the impurities have no influence on the possibility of Read Across for this end point. For further details refer to the Category Justification Report to the section 13 of the dossier.

Hydrolysis was determined at 50 °C at pH 4, 7 and 9 for the preliminary test in the analogous substance. The determination of residual test substance was performed by high performance liquid chromatography (HPLC) using an external standard. The test substance is stable at pH 4, 7 and 9 at 50 °C: it has a half-life period longer than one year at 25 °C at pH 4, 7 and 9 (Ciba-Geigy Ltd., 1992).