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EC number: 203-002-1
CAS number: 102-06-7
The partition coefficient of 1,3 Diphenylguanidine was first determined according to the OECD guideline 117, but this method may not applied to ionisable substance. Thus, a second study was performed in accordance with OECD testing guideline 107 and GLP requirements and at pH 11 ( i.e. one unit higher than the pKa). The partition coefficient of 1,3 Diphenylguanidine was 2.42 at pH 11
The partition coefficient of DPG
(1,3-diphenylguanidine) was evaluated in 2 studies.
The first one was performed in
accordance with OECD testing guideline 117 and GLP requirements. The
partition coefficient of 1,3-diphenylguanidine was > 6.2 at pH = 9.3 and
of 4.4 at pH = 7.01. This
result is different from the other log Kow values that have been
determined with other methods:
The difference of results between
these data suggest that the OECD 117 method may not be the most
appropriate for DPG. Indeed, as indicated in the Chapter R.7A of the
REACH guidance (Section R.126.96.36.199), the HPLC method is to be applied to
acids and bases in their non-ionised forms, although the pH should be
kept in the range to 2 to 9. But according to several publications, the
dissociation constant of DPG is about 10.13. That means that a pH of at
least 11.13 should be used during the log Kow measurement of DPG in
order to be in the presence of the non-ionized form.
Therefore, a more reliable method for
such substances is the shake-flask method (OECD 107) using an
appropriate buffer with a pH of at least one unit below (free acid) or
above (free base) the pKa. This
is why a second study according to OECD 107 guideline and GLP
requirements was performed for the determination of the Log Kow of DPG: the
partition coefficient was evaluated at pH 11 ( i.e. one unit higher than
the pK): Log Kow = 2.42.
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