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Hi
can anyone of you tell me the exact reason of using fresh Calibration
Curve for Stability exercises in bioanalytical method validation.
thanks in advance
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The following message was posted to: PharmPK
You should check your fresh curve with a single freeze-thaw to confirm
you have this stability. This is the reason you would first run a fresh
calibration curve.
Your SOPs should state what a baseline reading should be (most people
use frozen one time and run in a method no more then three days (72
hours) from initial freeze. Once you have this stability, you should
make a calibration curve every time you run stability, freeze it and run
in within the time stated in your SOP.
You always make a new one because this is what you are comparing it to
every time...you do not have stability so you can not use a calibration
curve that has been frozen longer then your SOP described baseline time.
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The following message was posted to: PharmPK
Hello,
The idea behind running a fresh calibration while assessing the
stability of an analyte in plasma or any other bio-matrix is to ensure
that the calibrants have not been exposed to any degradation process.
The standards are the bench-mark against which the stability samples are
measured. It is only if the calibrant stability have been previously
established (under a specific storage conditions) that these can be used
to assess stability of a new batch of stability samples.
The bottom line is that one does not want to introduce variability in
the measurements. In our lab, we assess QC stability by preparing a
fresh calibration curves plus fresh QC samples on top of the stability
samples. The fresh QC samples provide means to assess the accuracy of
the calibrants. The concentration of the stability samples is then
compared to the time zero measurements done right before these samples
are place in storage. The % difference between a given time point
concentration and that at time zero is taken as measure of the analyte
stability. All solution used in the preparation of the calibrants, QC,
etc are also checked against solutions prepared by a second analyst.
These solution must agree within a given specification in order to be
used in the process.
Hope this help
Luis
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The following message was posted to: PharmPK
In the beginning there is fresh and only fresh. You should
run fresh curves and fresh QCs for the first 5 of 6 A&P runs. The
sixth run should also be fresh but with the intent of using this run not
only to complete validation but also to certify excess material for use
as QCs. The QCs are "certified"- if they pass, and are then stored for
stability experiments in the validation and possbily for use in sample
analysis.
If you run frozen curves in validation you will be ignorant of the
impact of freezing on your material. Running frozen curves with frozen
QC is like building sand castles in the air and then choosing to live in
them.
--
Ed O'Connor, Ph.D.
Laboratory Director
Matrix BioAnalytical Laboratories
25 Science Park at Yale
New Haven, CT 06511
Web: www.matrixbioanalytical.com
Email: eoconnor.at.matrixbioanalytical.com
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Regarding the use of a freshly prepared set of calibration standards:
Aside from the good reasons stated by Franklin Spriggs and Luis, I
would note that for both stability studies and analysis of study
samples, it is a standard practice to prepare a fresh set of
calibration standards for each run. If standards and quality controls
are prepared at the same time and then stored, then any change in the
quantification (increase or decrease) of controls will very likely be
seen in the standards as well, so that the change would not be
apparent from using a set of stored (e.g., frozen) standards to
quantify a set of similarly stored quality controls. This would cause
an error in quantification for samples that were drawn and stored at a
different time. It is not only useful in detecting general, gradual
changes, but also for catching an isolated undetected event (e.g.,
undetected freezing and thawing in a freezer).
-Tom
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