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Dear All,
Right now I am working on molecule with its labelled internal standard
(D4),i want to know whether is it necessary to perform ion suppression
and matrix effect experiments while using labelled internal standard
(D4).
Thanks in Advance
T.S.Chandran
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Dear Chandran,
It is better to perform these parameters even using Labelled internal
standards.
Thanks
Dr Zafar
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Dear all,
There is at least one reported example of a case in which the stable
label internal standard (SLIS) did not correct for matrix effect:
Jemal et al, Rapid Commun Mass Spectrom (2003), 17: 1723-1734
It is therefore recommended to evaluate matrix effect even when using
a SLIS. I think the best way is to present data for analyte and
internal standard (based on area) and for normalised data (based on
area ratio). This way you may reveal matrix effect but then determine
whether the SLIS was efficient at correcting for it. You then can
decide with complete information if data is acceptable or it is best
to improve the methodology.
One of the most useful information the co-eluting SLIS provides is
that of its area during real sample analysis: monitoring SLIS absolute
area in all samples may reveal unexpected matrix effects occurring in
real samples, that are not present in spiked standards and QC samples.
Patrice
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Very well done. The stable label does not obviate all of the required
exercises: Demonstrations of absolute and relative recovery are needed
as is
linearity of response and stability.
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Dear all,
Is it still relevant to quantitate/estimate ion suppression even
though we are analyzing the samples in the presence of calibration
standards which may be having the ion suppression factor along with
them?
thanks
SP
Dept of pharmacokinetics
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Hmm-"may be" would be something your QA and certainly the FDA would get
excited about! You would like to demonstrate that the suppression
is the
same in samples and in calibrators.
You might also want to demonstrate the suppression is the same over your
entire curve, as well as in samples that need to be diluted into the
curve.
EOC
www.aegisbioconsult.com
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Absolutely.
The key issue is the assay accuracy, precision and reproducibility. Ion
suppression may (most likely) negatively impact the assay's accuracy,
precision and reproducibility. You stated that the suppression is
observed/characterized in the calibration standards. I would assume
that you
observed the same degree of suppression in QC samples too? The
problem is
that there is no way to fully characterize ion suppression in every test
sample, which may or may not have the same type/degree of suppression
observed in the calibration standards/QC samples you prepared in the
lab.
That is why the best approach is to eliminate/ avoid ion suppression
region
if possible.
Hope this help.
TK Chen
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