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The following message was posted to: PharmPK
Dear all,
thanks for your wonderful suggestions regarding conversion of drug
into metabolite.
i have one more question related to suppression effect.
"It is possible that Deuterated Internal standard can suppress the
response of drug,
or Drug can suppress the response of Deuterated Internal standard? i
want to know why it happens, what could be the corrective actions"
hoping for your wonderful suggestions
kanchan soni
veeda clinical research.
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The following message was posted to: PharmPK
The two events are the 1) efficiency of ionization and 2) the
detection of
those ions. Depending on the ratios of IS to A there is the potential
for
suppression.
You should examine this using both exaggerated ratios of IS to A and
ratios
that would simulate the levels you would actually find. Run them
separately, then in combinations to see if one effects the other.
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The following message was posted to: PharmPK
Yes, deuterated IS can suppress ionization efficiency of analyte similar
to auto-suppression of analyte by analyte at higher concentrations.
Electrospray ionization tends to be more sensitive to this phenomenon
IIRC.
Best regards,
Frederik
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The following message was posted to: PharmPK
Hi, Kanchan,
If you have a very high concentration of your analyte already
approaching the upper border of linear response then it will suppress
the response of your deuterated IS or anything co-eluting for that
matter.
Of cource, this will happen also vice versa: a very high concentration
of IS will attenuate the response of your analyte.
THis happens because only a specific ammount of ions can be formed in
ESI interface per unit of time. If the concentration is higher than the
ionisation capability of your ESI, then the response will no be linear
and at a certain point, the detector response will no longer increase
with increasing concentration. This happens usually in the range of
several tens of ug/mL (around 50-300 ng on column if you inject 5uL).
Therefore, it is not adviseable to use a very high concentration of IS
(0,1 - 1 ug/mL range is a good starting point).
Best regards,
Jurij Trontelj, Ph D
Faculty of Pharmacy
University of Ljubljana
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The following message was posted to: PharmPK
hi sir,
is there any corrective action or any experiment by which we can
identify how much suppression or remove the suppression of analyte or
IS??
kanchan
veeda clinical research
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The following message was posted to: PharmPK
You can identify the amount of suppression by comparing the response
of the
IS and of the X individually with the response when IS and X are
combined.
Identify the level at which you begin to get impact then ensure that
you do
not exceed that level. Any samples that exceed the level(s) will need
to be
repeated at a greater dilution. Optimize ionization and suppression
parameters using the worst case sample(s).
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The following message was posted to: PharmPK
Dear Kanchan,
I don't quite see what the problem is; if you run a properly designed
calibration curve, with IS, then any of the effects that you are worried
about will be accounted for. Obviously, from a common sense point, you
use a (fixed) level of IS that is neither 'screamingly' high nor low.
Best regards,
Frederik
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