tris (4-nonylphenol, branch) phosphorous acid ester

Hydrolysis

Description of key information

The hydrolysis endpoint for TNPP is very challenging to test as TNPP is highly insoluble in water. A true water solubility limit for TNPP has not been established and multiple attempts to have not been successful. Without being able to measure TNPP in water it is impossible to determine a hydrolysis rate.  However, in the most recent study (VU 2021) hydrolysis was inferred by observing more 4-nonylphenol, branched coming off of the generator column than would be expected by the amount present in the test substance.

 

 

In the draft EU Risk Assessment Report for TNPP (EU RAR 2008) that, "although it cannot be totally ruled out that there might be environmental conditions where hydrolysis could occur,hydrolysis of TNPP in the aquatic environment will not be considered as an important phenomenon. This is based on the expected very low water solubility of the substance that would not enable hydrolysis to occur in large amount. Furthermore, the high hydrophobicity of TNPP (high log Kow) will contribute to a large adsorption of the substance on sediment when entering the aquatic compartment thus reducing its availability for hydrolysis."  This conclusion is likely still valid for the most part, though the new study indicates that hydrolysis cannot be ruled out for TNPP and will likely occur when the conditions are favourable (i.e. high surface area between TNPP and water, lower pH, higher temperatures).