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EC number: 245-659-7
CAS number: 23432-62-4
The result was obtained using an appropriate QSAR method (see attached
QMRF and QPRF for details).
For detailed information on the results please refer to the attached
HYDROLYSIS EXPERIMENT (Tier 1 study)
Table 1: Hydrolysis Rate in Aqueous Sample (nominal concentration: 1000
µg test item/L, n=2).
Reaction rate constant k [1/s]
1.09 * 10-4
4.43 * 10-5
8.94 * 10-5
1.84 * 10-4
1.04 * 10-4
Hydrolysis half-life T1/2 [h]
ADSORPTION EXPERIMENT (Tier 3 study)
- As the test item stability in the test system is limited, no test
guideline experiments to determine the kinetics of adsorption
equilibrium have been conducted and the duration of the adsorption
experiments was set to 30 min. For the same reason, the desorption
isotherm was not determined.
mass balance was calculated from measured amounts of aqueous phase and
soil extracts and was between 44 and 74% (mean of all concentrations)
for all soils.
No adsorption was observed for the test item in the experiments with all
tested soils. At the end of the adsorption experiment, the measured
amount of test item in soil was lower than expected based on the residue
of the test item that was calculated to be in the remaining pore water.
This is assumed to be due to further hydrolysis occurring during sample
preparation. According ot the report determination of desorption data
for this test item according to the guideline is not useful because no
adsorption was observed. For this reason, no endpoints for desorption
are presented in this report.
Table 2: pH values of the aqueous
0.01 M CaCl2
after soil contact
after addition of the test item
[3-(trimethoxysilyl)propyl]carbamate (CAS 23432-62-4): no adsorption
potential (OECD 106)
(trihydroxysilyl)propyl]carbamate (silanol hydrolysis product): log Koc
= 0.57 (QSAR, PFA, 2019)
Methyl-N- [3-(trimethoxysilyl)propyl]carbamate (CAS 23432-62-4)
decomposes fast in the environment, due to rapid hydrolysis in contact
with water forming the corresponding hydrolysis products methyl-N-[3
(trihydroxysilyl)propyl]carbamate and methanol.
A study was conducted according to OECD 106 with the parent
substance in order to identify its adsorption/desorption properties
(2017). Five different soils were used for the experiments with pH
values between 5.5 and 7.2. Soils with pH close to neutral were chosen
since the substance is hydrolytically unstable and hydrolysis was
expected to be slowest for neutral pH. A Tier 1 test (hydrolysis rate in
aqueous samples) was conducted in order to check the stability of the
substance in the soils. The hydrolysis half-life was between 1 and 4.3
h. Due to fast hydrolysis a Tier 2 test (determination of adsorption
kinetics) was omitted and the study design of the Tier 3 (determination
of adsorption isotherms) test was adjusted according to the opinion
published by the scientific committee on plants on methods for the
determination of the organic carbon adsorption coefficient (KOC) for a
plant protection product active substance (SCP/KOC/002). The experiment
was conducted with five concentrations ranging from 0.2 to 20 mg test
item/L in order to determine the adsorption isotherms. The incubation
time was adjusted to 0.5 h due to fast hydrolysis of the substance. The
aqueous phase and the extracted solid phase were analyzed via LC-MS/MS
after the adsorption experiment. No adsorption was determined and
therefore no Koc values were calculated in the study.
Since the substance is hydrolytically unstable further information
on the adsorption behavior of the silanol hydrolysis product was
collected by two appropriate calculation methods.
In the first method the Koc was calculated with a prediction
method developed especially for organosilicon compounds including
N-containing substances (PFA, 2019). With this method a log Koc of 0.57
was calculated for the silanol hydrolysis product methyl-N-[3
(trihydroxysilyl)propyl]carbamate (neutral pH)
Considering the ionizing properties of the compound, the
adsorption potential has been additionally calculated using Franco and
Trapp ‘s expressions (2008) on estimation of the organic carbon-water
partitioning coefficient of ionisable organic substances. The adsorption
potential was calculated for pH 4, 7 and 9. The environmental relevant
pKa of the hydrolysis product determined with SPARC was 11.3. The
calculated log Koc of the hydrolysis product was -0.132 at pH 4, -0.13
at pH 7 and 0.118 at pH 9.
Both the experimental study for the parent substance and the QSAR
calculations with the hydrolysis product reveal a negligible adsorption
potential in soils and sediments.
Since the hydrolysis of the substance at pH 4, 5 and 9 was
identified to be very fast it is assumed that under environmental
conditions the hydrolysis product will be the dominant species present
and therefore its log Koc values are considered more appropriate for the
chemical safety assessment.
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