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EC number: 629-661-9 | CAS number: 83834-59-7
Remark on reaction rates, DT50 and quantum yields in table 20 and figure 14, 15 and 16 (see attached background material). Results where calculated based on TLC I, second irradiation study results.A major part of the activity appeared to adsorb onto testing equipment.Part of the adsorbed activity could be resolved (rinsing with organic solvents), but the rinsates were not analysed on TLC to retreive distribution of parent and metabolites. Hence, in order to calculate the degradationrate of 2-Ethylhexyl 4-methoxycinnamate the following two approaches were used:
1) "On plate": (low limit): the adsorbed activity could show the same distribution as found in the test solution. It was calculated using % distribution on plate.
2) "Of applied": (high limit): The adsorbed activity could consist of metabolites only. In this case degradation rate was calculated using % distribution of applied.
According to the authors thus a lower limit and a higher limit could be found, in wich region the actual degradation rate can be found.
Since the dark control did not show degradation, the degradation rates as obtained were equal to the final photolytic rates.
The quantum yield reported was between 1*10 -5 and 2*10 -5.
The photolytic degradation of 2-Ethylhexyl 4-methoxycinnamate was studied by irradiation of a test solution of 0.12 mg/L 2-Ethylhexyl 4-methoxycinnamate in milli-Q water and 20 % acetonitrile (to prevent hydrolysis) with a xenon lamp for 23 days, which was equivalent with 21 days in sunlight in a closed system .The test substance was radioactivily marked on its phenyl ring. TLC and a scintillation counter were used for seperation and identification of parent and metobalites.TLC plates were scanned and areas integrated for quantification. The mass balance decreased from 92 % at t = 0 to 52 % at t = 23 days, according to the authors due to adsorption to the test equipment. Comparison of the retention of reference substances and the metabolites on TLC was used for identification. pH temperature and sterility were monitored and kept stable. Light intensity was verified with an actinometre. See Conlusions for the final results.
Phototransformation in water: DT50 = 5 - 9 days (EPA Guideline Subdivision N 161-2 (Photodegradation Studies in Water))
According to the classification scheme by Mensink, trans-2-Ethylhexyl 4-methoxycinnamate can be regarded as being very rapidly degradable when transition to cis-2-Ethylhexyl 4-methoxycinnamate is taken into account.
When trans-cis transition is left out, 2-Ethylhexyl 4-methoxycinnamate can be classified as fairly degradable with a DT50 in the range of ca. 5 - 9 days. The main photolytic degradation products are p-methoxycinnamate (34.8 % applied initial substance), unidentifiable substances M1 and M3 (according to TLC method I) or MA, MB and MD (according to TLC method II). The quantum yield for the trans-to-cis conversion was 0.0021. The quantum yield for the degradation into metabolites appeared to be in the range of 1*10^-5 to 2*10^-5.
It is concluded that the test substance is fairly degradable by phototransformation in water.
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