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EC number: 203-733-6
CAS number: 110-05-4
Due to the results of the preliminary
test, the log PBOWBof
Di-tert-butyl peroxide (CAS# 110-05-4) at 22 °C was estimated to be in
the range of about 1.4 and 1.9. On sponsor’s request, the shake flask
method was chosen to conduct the main test.
During the main study, three tests
were carried out, each in duplicate, with volume ratios of both solvents
of 1:1, 2:1 and 1:2. After equilibration the concentration of the test
item was determined in every phase by GC-MS. The results of the
individual measurements are summarized in Table 2X.
The tabulated values represent rounded results, which were obtained by
calculation using the exact raw data. The log PBOWBwas
calculated for each of the six vessels and was found to be in the range
of 3.14 to –3.27. Details are given in Table 2X.
In order to check the analytical work,
the mass balance for each vessel was calculated, too, and the recovery
of the test item was found to be in the range of 108% to 124%.Details
are given in Table 3X.
The tabulated results represent rounded-off values obtained by
calculations based on the exact raw data.
A typical chromatogram of a standard
solution of the water matrix is given in attached Figure 1X.
A typical chromatogram of a standard solution of the n-octanol matrix is
given in attached Figure2X.
A typical chromatogram of an aqueous sample solution is given in
attached Figure 3 and of a sample solution in n-octanol in attached
A typical GC-MS chromatogram of a blank solution is shown in attached
An example of a calibration curve and the data for test item-standards
used for water matrix is given in attached Figure 6 and Table 4 and used
for n-octanol matrix is given in attached Figure7 and Table5X.
The correlation coefficient rP2P
in water was 0.9984 and in n-octanol was 0.9992
(optimum 1.0000). This reflects the linearity of the GC-MS-system within
the calibration range of 0.037 µg/mL to 0.615 µg/mL of the test item in
water matrix and of 0.308 µg/mL to 2.153 µg/mL of the test item in
Table2 Calculation of the log PBOWB
Concentration of thetest item found
pH of the aqueousphase
Mean value (rounded) =
Standard deviation = ±
n.a. = not available. Sample 4 could
not be evaluated because of an injection error.
Table3 Mass Balance for the
Determination of the log PBOWB
Concentrationof test item
Mass of test item
of test item inboth phases
test item added
Vessels containing water and n-octanol
with volume ratios of 1:1, 2:1 and 1:2 were shaken for 30 minutes at
room temperature. Afterwards the samples were centrifuged and
equilibrated for another 1 hour at room temperature. After dilution with
acetonitrile the concentrations in both phases were determined by a
GC-MS method. From the results obtained the n-octanol / water partition
coefficient (log PBOWB)
of Di-tert-butyl peroxide (CAS# 110-05-4) was calculated to be
log PBOWB = 3.20
at 22 °C
Standard Deviation =±0.05
The pH in the aqueous phase was 7.2.
Di-tert-butyl peroxide has an octanol-water partition coefficient of log Pow 3.2.
See:110-05-4, Partition coefficient (shake
flask method), Elsner 2010, rs.
The partition coefficient was also
determined by the HPLC method (Nijenhuis, 2010). In that study, the log
Pow was found to be 5.2. The Nijenhuis study has been designated as a
supporting study. Although the study was valid (Klimisch 1), the data
are inconsistent with the water solubility of 170 mg/l and the two
calculated values for the log Kow (3.45 and 1.5).
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