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EC number: 240-400-4
CAS number: 16324-27-9
tested substance is estimated as hydrolytically 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. The substance has not hydrolysable chemical groups within
the chemical structure.
Based on calculations according to AOPWIN
v1.92, the substance is indirectly photodegraded by reaction with
hydroxyl radicals in the atmosphere with half-lives of about 0.6 hours
taking into account a 12-h day.
dilute solutions and in presence of sunlight, the substance undergoes
reversible isomerisation of the stilbene moiety.In this process, two
isomeric forms occur. The E- and Z-isomers are under environmental
conditions in equilibrium within a few minutes. The parent substance
consists of the E-isomer, while isomerisation to the Z-form leads to
complete loss of fluorescence. The isomerisation process appears to play
a major role in the photochemical behaviour. A constant isomer mixture
is maintained during photochemical degradation processes. Since the
photoisomerisation process is temperature - as well as wavelength-
dependent, the isomer distribution changes in sunlit natural waters with
season (temperature) and depth (wavelength).
studies (for OB 2 -A and OB 3a-MSA) demonstrate that at solar latitude
60 °C, at 25 °C, and on surface layer depths of 0 to 5 m the remaining
E-isomer fraction is 13.9 to 9.5 and 17.8 to 13.3, respectively. The
preceding isomer equilibrium influences the photo-degradation rate. The
half-life for photo-oxidation in natural water was measured for the same
substances and under the same light conditions on the surface layer: 278
min (OB 2 -A) and 313 min (OB 3a-MSA).
Based on measured kinetic parameters and the quantum yield,
photochemical half-lives in three Swiss lakes are calculated according
to GCSOLAR as a function of surface layer depth and time of the year.
Both substances degrade with nearly identical half-lives. Therefore, it
is assumed that all substances of the category follow the same
photolytic processes and are effectively degraded in surface waters.
processes induced by sunlight are effective in degrading the substance.
The photodegradation importance in water does however strongly depend on
the light screening of the water constituents. The presence of suspended
solids or sediments in natural waters does not seem to have a major
impact on the photoreactivity of the substance. The extent of adsorption
at environmental relevant pHs is rather small. Thus, the small amounts
of particles in the photic zone of natural surface waters are not
capable of adsorbing larger amounts of the substance tested. The
particles may however reduce the availability of light for the substance
tested since they adsorb light themselves.
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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