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EC number: 273-227-8
CAS number: 68953-84-4
Water solubilities for the 3 main constituents of 1,4-benzenediamine, N,N'-mixed Ph and tolyl derivatives are: 0.13, 0.11 and 0.045 mg/L.N,N'-diphenyl-p-phenylenediamine; R-59; CAS: 74-31-7: 0.13 mg/L;N-(2-methylphenyl)-N'-phenylbenzene-1,4-diamine; R-1679; CAS: 27173-16-6: 0.11 mg/L;N,N'-bis(2-methylphenylbenzene)-1,4-diamine; R-898; CAS: 15017-02-4: 0.045 mg/L
The water solubility for DAPD, 0.095 mg/L, was calculated as the average
of water solubilities of the 3 main components.
The water solubility of 1,4-benzenediamine, N,N’-mixed phenyl and tolyl
derivatives was tested using two different testing protocols. A first
test used the Column Elution method as described in the OECD protocol n°
105 in combination with a GC analysis of the saturated solution. In the
second test, a saturated solution of test substance was created via the
flask method and analyzed by total carbon measurement, in accordance
with EU protocol A6. Due to the difference in test setup and analytical
technique used, the two test procedures lead to fundamentally different
values for the water solubility of 1,4-benzenediamine, N,N’-mixed phenyl
and tolyl derivatives.
Difference in the composition of the saturated test solution.
It should be noted that both techniques used to create a saturated test
solution are specifically suitable for the examination of pure
substances. However, as 1,4-benzenediamine, N,N’-mixed phenyl and tolyl
derivatives is a multi-constituent substance, the application of both
protocols leads to test solutions that are not identical in composition.
When using the flask method, in which a large amount of ground test
substance (> 5 times than the estimated amount that would dissolve) is
brought into contact with a certain amount of water and stirred for 24
hours, the watery solution will be enriched in the soluble constituents
or impurities present in the multi-constituent substance.
The protocol for the column elution method describes that the first 5
bed volumes of water eluted from the column should be removed, in order
to remove any highly soluble substances present in the test material. As
a consequence, the watery solution will be depleted in the highly
soluble impurities or constituents.
Difference in analytical technique used.
Both the total carbon measurement and GC analysis are considered to be
valid and suitable methods for analyzing the amount of test substance
dissolved in the saturated test solution. However, the total carbon
measurement will lead to one value for the multi-constituent substance
“1,4-benzenediamine, N,N’-mixed phenyl and tolyl derivatives” as such,
whereas the GC analysis will differentiate between the substance’s main
constituents and impurities.
As a consequence, by using the column elution technique in combination
with GC analysis the total water solubility of DAPD is underestimated,
as the soluble impurities that are part of the composition of DAPD are
not taken into account. The technique does however give a reliable
estimation of the water solubilities of the 3 main constituents of DAPD.
On the other hand, the flask elution method in combination with total
carbon measurements clearly overestimates the water solubility of the
testing substance, as the tested solution is enriched in highly soluble
impurities and total carbon measurement does not differentiate between
the impurities and the main constituents.
Adequacy for the purpose of chemical safety assessment.
It can be concluded that neither of both techniques described above
would lead to a good estimation of this “overall” water solubility value.
Upon assessing the adequacy of the available test results for the
purpose of the risk assessment it needs however to be taken into account
that separate exposure scenarioʼs have been built for each of the main
constituents of the multi-constituent substance. As a consequence,
specific water solubility values for the 3 main constituents are to be
taken into account in these exposure assessments. In a final stage of
the risk assessment, the results of the 3 separate assessments are then
combined to come to one overall conclusion. It is therefore relevant for
the risk assessment process to have the 3 separate water solubility
values for the main constituents of DAPD.
Based on the above reasoning the column elution test combined with GC
analysis was assigned as key study.
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