1,3'-Bipyridinium, 5'-[[4-[[4-[(1',2'-dihydro-6'-hydroxy-3,4'-dimethyl-2'-oxo[1,3'-bipyridinium]-5'-yl)azo]benzoyl]amino]phenyl]azo]-1',2'-dihydro-6'-hydroxy-3,4'-dimethyl-2'-oxo-, salt with 2-hydroxypropanoic acid (1:2)

Hydrolysis

Description of key information

The substance is expected to be stable under natural conditions of pH and temperature.

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 the Basic Orange 064, it is likely that hydrolysis can be considered as negligible degradation pathway, due to the chemical structure and functional groups presents. The substance is a cationic azo dye, which has an amide group in the middle of two symmetrical moieties.

The amide functional group is expected to be hydrolysable under acid/basic conditions; however, at common natural pH conditions it is expected to be hydrolitically stable.

During the validation of analytical method experiment, conducted to analyze the test item in distilled water, ecotox medium and n-octanol, specific assays were performed to assess the test item stability: Basic Orange 064 resulted to be stable in distilled water at the temperature 15 - 25 °C for 24 hours and at the temperature 2 - 8 °C for 3 days.

However, no specific experiments were conducted on the hydrolisis potential of Basic Orange 064, therefore, the available information on Similar Substance 03 have been taken into consideration in order to support and confirm the expected substance behavior. Taking into consideration the aim of the approach, the read across can be considered as suitable and appropriate (details given in the documents attached to the IUCLID section 13).

The hydrolysis determination of the Similar Substance 03 at different pH values was conducted in accordance with the OECD guideline 111 and the EU method C.7. The solubility of the substance at pH 4.0 resulted to be very low, thus the measurements cannot be performed. The results at pH 7.0 showed no significant degradation at 50 °C. The substance was found to be not stable at pH 9.0; the degradation after 2.4 hours was higher than 50 %. It was concluded that the estimated half-life time at pH 7.0 is higher than one year under representative environmental conditions (25 °C).

In conclusion, the available information on the analogue, which is characterized by a similar chemical structure, confirmed that Basic Orange 064 can be considered as hydrolitically stable, under environmental common conditions.