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EC number: -
CAS number: -
Alkyl phosphites are expected to hydrolyze readily under most
conditions. Data on tris alkyl phosphites of similar composition
(triisodecyl phosphte (TDP) and triisotridecyl phosphite (TiTDP)) show
half-lives ranging from 0.43 hr (pH 1.2) to 20.1 hrs (pH 9). Additional
data on other phosphites also support the conclusion that this substance
It has been well established
through a series of modified tests and practical handling experience
that this class of alkyl phosphites readily hydrolyses. ECHA actually
notes in its REACH Guidance R.11 on PBT assessment that phosphites are a
class of substances that are known to hydrolyse in the environment.
Unfortunately, it is actually
very hard to test phosphites for their hydrolysis rates in the standard
OECD guideline (111) due to the extremely low water solubility of the
substances. The registrant sought to place the ECHA requested OECD 111
guideline test on TiTDP with an accredited laboratory but, after much
discussion with the laboratory, it was decided that the very low water
solubility of TiTDP would render it unsuitable for this test method.
A new comparative study of the
hydrolysis of TiTDP and TDP (Carraz 2014) was just conducted to both
draw a comparison of the relative rates of hydrolysis between the two
phosphites and also to evaluate the rate of hydrolysis in simulated
stomach acid (pH=1.2). In this study, it was found that using a
co-solvent, 50% acetone in solution, greatly increased the reliability
of the results likely because the co-solvent helped make the phosphites
available to the aqueous phase allowing hydrolysis to occur. From this
study,TiTDP with a t1/2of 0.43 hour hydrolysed more rapidly
than TDP with a t1/2of 2.44 hours.
By comparison, the Reimer (2002)
hydrolysis test of TDP, using 50% acetonitrile as a co-solvent, gave a
half-life of 4.1 hours at pH 5, 17 hours at pH 7 and 20.1 hours at pH 9
at ambient temperature. The shorter half-life at lower pH is to be
expected given that the hydrolysis of organophosphites is known to be
The results from Carraz (2014)
indicate that TiTDP has a similar, perhaps slightly faster, rate of
hydrolysis than TDP. As such, these data support the use of the Reimer
(2002) results on TDP for TiTDP dossier. The Carraz data also indicate
that TiTDP and TDP will behave similarly in the stomach, further
supporting the justification for using TDP toxicity data for TiTDP
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
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